Antbird
Encyclopedia
The antbirds are a large family
, Thamnophilidae, of passerine
bird
s found across subtropical and tropical Central and South America, from Mexico to Argentina. There are more than 200 species, known variously as antshrikes, antwrens, antvireos, fire-eyes, bare-eyes and bushbirds. They are related to the antthrushes and antpittas (family Formicariidae
), the tapaculo
s, the gnateater
s and the ovenbirds
. Despite some species' common names, this family is not closely related to the wren
s, vireo
s or shrike
s.
Antbirds are generally small birds with rounded wings and strong legs. They have mostly sombre grey, white, brown and rufous
plumage
, which is sexually dimorphic
in pattern and colouring. Some species communicate warnings to rivals by exposing white feather patches on their backs or shoulders. Most have heavy bills
, which in many species are hooked at the tip.
Most species live in forests, although a few are found in other habitats. Insect
s and other arthropods form the most important part of their diet, although small vertebrates are occasionally taken. Most species feed in the understory
and midstory of the forest, although a few feed in the canopy
and a few on the ground. Many join mixed-species feeding flocks, and a few species are core members. To various degrees, around eighteen species specialise in following
columns of army ant
s to eat the small invertebrate
s flushed by the ants, and many others may feed in this way opportunistically.
Antbirds are monogamous
, mate for life, and defend territories
. They usually lay two eggs in a nest that is either suspended from branches or supported on a branch, stump, or mound on the ground. Both parents share the tasks of incubation
and of brooding and feeding the nestlings. After fledging
, each parent cares exclusively for one chick.
Thirty-eight species are threatened with extinction as a result of human activities. Antbirds are not targeted by either hunters or the pet trade. The principal threat is habitat loss
, which causes habitat fragmentation
and increased nest predation in habitat fragments.
that included antthrush
es and antpitta
s. Formerly, that larger family was known as the "antbird family" and the Thamnophilinae were "typical antbirds". In this article, "antbird" and "antbird family" refer to the family Thamnophilidae.
Thamnophilidae was removed from Formicariidae, leaving behind the antthrushes and antpittas, due to recognition of differences in the structure of the breastbone (sternum
) and syrinx
, and Sibley and Ahlquist's examination of DNA-DNA hybridisation. The Thamnophilidae antbirds are members of the infraorder Tyrannides (or tracheophone suboscines
), one of two infraorders in the suborder Tyranni. The Thamnophilidae are now thought to occupy a fairly basal
position within the infraorder, i. e. with regard to their relatives the antthrushes and antpittas, tapaculo
s, gnateater
s, and also the ovenbirds
. The sister group of the Thamnophilidae is thought to be the gnateaters. The ovenbirds, tapaculos, antthrushes and antpittas are thought to represent a different radiation of that early split.
The antbird family contains over 200 species, variously called antwrens, antvireos, antbirds and antshrikes. The names refer to the relative sizes of the birds (increasing in the order given, though with exceptions) rather than any particular resemblance to the true wren
s, vireo
s or shrike
s. In addition, members of the genus Phlegopsis are known as bare-eye
s, Pyriglena as fire-eye
s and Neoctantes and Clytoctantes as bushbird
s. Although the systematics of the Thamnophilidae is based on studies from the mid-19th century, when fewer than half the present species were known, comparison of the myoglobin
intron
2, GAPDH
intron 11 and the mtDNA
cytochrome b
DNA sequences has largely confirmed it. There are two major clade
s – most antshrikes and other larger, strong-billed species as well as Herpsilochmus
, versus the classical antwrens and other more slender, longer-billed species – and the monophyly
of most genera was confirmed.
The Thamnophilidae contains several large or very large genera
and numerous small or monotypic ones. Several, which are difficult to assign, seem to form a third, hitherto unrecognised clade independently derived from ancestral antbirds. The results also confirmed suspicions of previous researchers that some species, most notably in Myrmotherula
and Myrmeciza
, need to be assigned to other genera. Still, due to the difficulties of sampling from such a large number of often poorly known species, the assignment of some genera is still awaiting confirmation.
The antbirds are a group of small to medium-sized passerine
s that range in size from the large Giant Antshrike
, which measures 45 cm (18 in) and weighs 150 g
(5.29 oz
), to the tiny 8-cm (3 in) Pygmy Antwren
, which weighs 7 g (0.25 oz). In general terms, "antshrikes" are relatively large-bodied birds, "antvireos" are medium-sized and chunky, while "antwrens" include most smaller species; "antbird" genuses can vary greatly in size. Members of this family have short rounded wings that provide good manoeuvrability when flying
in dense undergrowth. The legs are large and strong, particularly in species that are obligate ant-follower
s. These species are well adapted to gripping vertical stems and sapling
s, which are more common than horizontal branches in the undergrowth, and thus the ability to grip them is an advantage for birds following swarms of army ants. The claws of these antbirds are longer than those of species that do not follow ants, and the soles of some species have projections that are tough and gripping when the foot is clenched. Tarsus
length in antbirds is related to foraging strategy. Longer tarsi typically occur in genera such as the Thamnophilus
antshrikes that forage by perch-gleaning
(sitting and leaning forward to snatch insects from the branch), whereas shorter tarsi typically occur in those that catch prey on the wing, such as the Thamnomanes
antshrikes.
Most antbirds have proportionately large, heavy bills
. Several genera of antshrike have a strongly hooked tip to the bill, and all antbirds have a notch or 'tooth' at the tip of the bill which helps in holding and crushing insect prey. The two genera
of bushbirds have upturned chisel-like bills.
The plumage
of antbirds is soft and not brightly coloured, although it is occasionally striking. The colour palette of most species is blackish shades, whitish shades, rufous, chestnut and brown. Plumages can be uniform in colour or patterned with barring or spots. Sexual dimorphism
– differences in plumage colour and pattern between males and females – is common in the family. Overall the pattern within the family is for the males to have combinations of grey, black or white plumage and the females having buff, rufous and brown colours. For example, the male Dot-winged Antwren
is primarily blackish, whereas the female has rust-coloured underparts. In some genera, such as Myrmotherula, species are better distinguished by female plumage than by male. Many species of antbirds have a contrasting 'patch' of white (sometimes other colours) feathers on the back (known as a interscapular patches), shoulder or underwing. This is usually concealed by the darker feathers on the back but when the bird is excited or alarmed these feathers can be raised to flash the white patch. Dot-winged Antwrens puff out white back patches, whereas in Bluish-slate Antshrike
s and White-flanked Antwren
s the white patch is on the shoulder.
) which have simpler syrinxes
("voiceboxes") than other songbirds. Nevertheless their songs are distinctive and species-specific, allowing field identification by ear. Antbirds rely on their calls for communication, as is typical of birds in dark forests. Most species have at least two types of call, the loudsong and the softsong. The functions of many calls have been deduced from their context; for example some loudsongs have a territorial purpose
and are given when birds meet at the edges of their territories, or during the morning rounds of the territory. Pairs in neighbouring territories judge the proximity of rivals by the degradation of the song caused by interference by the environment. In bouts of territorial defence the male will face off with the other male and the female with her counterpart. Loudsong duets are also potentially related to the maintenance of pair bonds. The functions of softsongs are more complex, and possibly related to pair-bond maintenance. In addition to these two main calls a range of other sounds are made; these include scolding in mobbing of predators. The calls of antbirds are also used interspecifically. Some species of antbirds and even other birds will actively seek out ant-swarms using the calls of some species of ant-followers as clues.
The distribution of the antbirds is entirely Neotropical, with the vast majority of the species being found in the tropics. A few species reach southern Mexico and northern Argentina. Some species, such as the Barred Antshrike
, have a continental distribution that spans most of the South and Middle American
distribution of the family; others, such as the Ash-throated Antwren
, have a tiny distribution.
Antbirds are mostly birds of humid lowland rainforest
s. Few species are found at higher elevations, with less than 10% of species having ranges above 2000 m (6500 ft) and almost none with ranges above 3000 m (10000 ft). The highest species diversity is found in the Amazon Basin
, with up to 45 species being found in single locations in sites across Brazil
, Colombia
, Bolivia
and Peru
. The number of species drops dramatically towards the further reaches of the family's range; there are only seven species in Mexico, for example. Areas of lower thamnophilid diversity may contain localised endemics, however. The Yapacana Antbird
, for example, is restricted to the stunted woodlands that grow in areas of nutrient-poor white-sand soil
(the so-called Amazonian caatinga
) in Brazil, Venezuela and Colombia. Some species are predominantly associated with microhabitats within a greater ecosystem; for example, the Bamboo Antshrike
is predominantly found in bamboo patches.
, a behaviour in which ants (or other arthropods) are rubbed on the feathers before being discarded or eaten. While this has conventionally been considered a way to remove and control feather parasite
s, it has been suggested that for antbirds it may simply be a way to deal with the distasteful substances in prey items.
The main component of the diet of all antbirds is arthropod
s. These are mostly insects, including grasshoppers and crickets, cockroaches, praying mantises, stick insects and the larvae of butterflies and moths. In addition antbirds often take spiders, scorpions and centipedes. They swallow smaller prey items quickly, whereas they often beat larger items against branches in order to remove wings and spines. Larger species can kill and consume frog
s and lizard
s as well, but generally these do not form an important part of the diet of this family. Other food items may also be eaten, including fruit, eggs and slugs.
The family uses a number of techniques to obtain prey. The majority of antbirds are arboreal
, with most of those feeding in the understory
, many in the middle story and some in the canopy
. A few species feed in the leaf litter
; for example, the Wing-banded Antbird
forages in areas of dense leaf-litter. It does not use its feet to scratch the leaf litter, as do some other birds; instead it uses its long bill to turn over leaves rapidly (never picking them up). The antbirds that forage arboreally show a number of techniques and specialisations. Some species perch-glean
, perching on a branch watching for prey and snatching it by reaching forward, where others sally
from a perch and snatch prey on the wing. In both cases birds will hop through the foliage or undergrowth and pause, scanning for prey, before pouncing or moving on. The time paused varies, although smaller species tend to be more active and pause for shorter times.
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Many species participate in mixed-species feeding flocks, forming a large percentage of the participating species within their range. Some of these are core or "nuclear species". These nuclear species share territories with other nuclear species but exclude conspecific
s (members of the same species) and are found in almost all flocks; these are joined by "attendant species". Loud and distinctive calls and conspicuous plumage
are important attributes of nuclear species as they promote cohesion in the flock. The composition of these flocks varies geographically; in Amazonia species of Thamnomanes
antshrike are the leading nuclear species; elsewhere other species, such as the Dot-winged Antwren
s and Checker-throated Antwren
s, fill this role. Other species of antwren and antbird join them along with woodcreeper
s, ant-tanagers, foliage-gleaner
s and greenlet
s. The benefits of the mixed flock are thought to be related to predation
, since many eyes are better for spotting predatory hawks and falcons. Comparisons between multi-species feeding flocks in different parts of the world found that instances of flocking were positively correlated with predation risk by raptors. For example, where Thamnomanes antshrikes lead the group they give loud warning calls in the presence of predators. These calls are understood and reacted to by all the other species in the flock. The advantage to the Thamnomanes antshrikes is in allowing the rest of the flock, which are typically gleaners, to act as beaters, flushing prey while foraging which the antshrikes can obtain by sallying. Similar roles are filled in other flocks by other antbird species or other bird families, for example the shrike-tanager
s. Within the feeding flocks competition
is reduced by microniche partitioning
; where Dot-winged Antwrens, Checker-throated Antwrens and White-flanked Antwren
s feed in flocks together, the Dot-wings feed in the densest vines, the White-flank in less dense vegetation, and the Checker-throats in the same density as the latter but in dead foliage only.
Swarms of army ant
s are an important resource used by some species of antbird, and the one from which the family's common name is derived. Many species of tropical ant
form large raiding swarms, but the swarms are often nocturnal or raid underground. While birds visit these swarms when they occur, the species most commonly attended by birds is the Neotropical species Eciton burchellii
, which is both diurnal and surface-raiding. It was once thought that attending birds were actually eating the ants, but numerous studies in various parts of E. burchellii's range has shown that the ants act as beaters, flushing insects, other arthropods and small vertebrates into the waiting flocks of "ant-followers". The improvement in foraging efficiency can be dramatic; a study of Spotted Antbird
s found that they made attempts at prey every 111.8 seconds away from ants, but at swarms they made attempts every 32.3 seconds. While many species of antbirds (and other families) may opportunistically feed at army ant swarms, 18 species of antbird are obligate ant-followers, obtaining most of their diet from swarms. With only three exceptions, these species never regularly forage away from ant swarms. A further four species regularly attend swarms but are as often seen away from them. Obligate ant-followers visit the nesting bivouacs of army ants in the morning to check for raiding activities; other species do not. These species tend to arrive at swarms first, and their calls are used by other species to locate swarming ants.
Because army ants are unpredictable in their movements, it is impractical for obligate ant-followers to maintain a territory
that always contains swarms to feed around. Antbirds have evolved
a more complicated system than the strict territoriality of most other birds. They generally (details vary among species) maintain breeding territories but travel outside those territories in order to feed at swarms. Several pairs of the same species may attend a swarm, with the dominant pair at the swarm being the pair which holds the territory that the swarm is in. In addition to competition within species, competition among species exists, and larger species are dominant. In its range, the Ocellated Antbird
is the largest of the obligate ant-following antbirds and is dominant over other members of the family, although it is subordinate to various species from other families (including certain woodcreeper
s, motmot
s and the Rufous-vented Ground Cuckoo). At a swarm, the dominant species occupies positions above the central front of the swarm, which yields the largest amount of prey. Smaller, less dominant species locate themselves further away from the centre, or higher above the location of the dominant species, where prey is less plentiful.
, in almost all cases forming pair bond
s that last the life of the pair. Studies of the Dusky Antbird
and the White-bellied Antbird
did not find "infidelity". In the White-plumed Antbird
divorces between pairs are common, but, as far as known, this species is exceptional. In most species the pair defends a classic territory
, although the nesting territories of ant-followers are slightly different (see feeding above). Territories vary in size from as small as 0.5 ha for the Manu Antbird
, to 1500 m (5000 ft) in diameter for the Ocellated Antbird. Ocellated Antbirds have an unusual social system where the breeding pair forms the nucleus of a group or clan that includes their male offspring and their mates. These clans, which can number up to eight birds, work together to defend territories against rivals. Pair bonds are formed with courtship feeding, where the male presents food items to the female. In Spotted Antbirds males may actually feed females sufficiently for the female to cease feeding herself, although she will resume feeding once copulation has occurred. Mutual grooming also plays a role in courtship in some species.
The nesting and breeding biology of antbirds have not been well studied. Even in relatively well-known species the breeding behaviour can be poorly known; for example the nest of the Ocellated Antbird
was first described in 2004. Nests
are constructed by both parents, although the male undertakes more of the work in some species. Antbird nests are cups of vegetation such as twigs, dead leaves and plant fibre, and they follow two basic patterns: either suspended or supported. Suspended cups, which may hang from forks in branches, or between two branches, are the more common style of nest. Supported nests rest upon branches, amongst vines, in hollows, and sometimes on mounds of vegetation on the ground. Each species nests at the level where it forages, so a midstory species would build its nest in the midstory. Closely related species nest in the same ways. For example antvireos in the genus Dysithamnus
are all suspension nesters.
Almost all antbirds lay two eggs. A few species of antshrike lay three eggs, and a smaller number of antbirds lay one egg, but this is unusual. Small clutch sizes are typical of tropical birds compared to more temperate species of the same size, possibly due to nest predation, although this is disputed. Both parents participate in incubation
, although only the female incubates at night. The length of time taken for chicks to hatch is 14–16 days in most species, although some, such as the Dusky Antbird
, can take as long as 20 days. The altricial
chicks are born naked and blind. Both parents brood the young until they are able to thermoregulate
, although, as with incubation, only the female broods at night. In common with many songbirds, the parents take faecal sacs for disposal away from the nest. Both parents feed the chicks, often bringing large prey items. When the chicks reach fledging
age, after 8–15 days, attending parents call their chicks. As each chick leaves the nest it is cared for exclusively from then on by the parent that was present then. After the first chick fledges and leaves with a parent the remaining parent may increase the supply of food to speed up the process of fledging. After fledging, chicks spend the first few days well hidden as the parents bring them food. Chicks of some species may not become independent of the parents for as long as four months in some antwrens, but two months is more typical for the rest of the family.
. They are preyed upon by birds of prey
, and their tendency to join flocks is thought to provide protection against such predation. The Greater Round-eared Bat
preys on some antbird species, such as the White-bibbed Antbird
and the Scaled Antbird
; the latter is the bat's preferred prey. Nests, including incubating adults, chicks and eggs, are vulnerable to predators, particularly snake
s but also nocturnal mammals. Nesting success is low for many species, particularly in areas of fragmented habitat.
It was once suggested that the relationship between the obligate and regular ant-followers and the army ants, particularly Eciton burchellii, was mutualistic, with the ants benefiting by having the birds chase prey back down towards them. However, experiments where ant-followers were excluded have shown that the foraging success of the army ants was 30% lower when the birds were present, suggesting that the birds' relationship was in fact parasitic
. This has resulted in a number of behaviours by the ants in order to reduce kleptoparasitism
, including hiding of secured prey in the leaf litter and caching of food on trails. It has been suggested that the depressive effect of this parasitism slows the development of E. burchellii swarms and in turn benefits other ant species which are preyed upon by army ants. The ant-following antbirds are themselves followed by three species of butterfly
in the family Ithomiinae
which feed on their droppings
. Bird droppings are usually an unpredictable resource in a rainforest, but the regular behaviour of ant-followers makes the exploitation of this resource possible.
As of April 2008, 38 species are considered by the IUCN to be near threatened
or worse and therefore at risk of extinction
. Antbirds are neither targeted by the pet trade nor large enough to be hunted; the principal cause of the decline in antbird species is habitat loss
. The destruction or modification of forests has several effects on different species of antbirds. The fragmentation of forests into smaller patches affects species that are averse to crossing gaps as small as roads. If these species become locally extinct in a fragment, this reluctance to cross unforested barriers makes their re-establishment unlikely. Smaller forest fragments are unable to sustain mixed-species feeding flocks, leading to local extinctions. Another risk faced by antbirds in fragmented habitat is increased nest
predation. An unplanned experiment in fragmentation occurred on Barro Colorado Island
, a former hill in Panama
that became an isolated island during the flooding caused by the creation of the Panama Canal
. Numerous species of antbird formerly resident in the area were extirpated
, in no small part due to increased levels of nest predation on the island. While the species lost from Barro Colorado are not globally threatened, they illustrate the vulnerability of species in fragmented habitats and help explain the declines of some species. The majority of threatened species have very small natural ranges. Some are also extremely poorly known; for example the Rio de Janeiro Antwren
is known only from a single specimen
collected in 1982, although there have been unconfirmed reports since 1994 and it is currently listed as critically endangered
. Additionally, new species are discovered at regular intervals; the Caatinga Antwren
was described in 2000, the Acre Antshrike
in 2004, the Sincorá Antwren
in 2007, and the description of a relative of the Paraná Antwren
discovered in 2005 in the outskirts of São Paulo
is being prepared. While not yet scientifically described, conservation efforts have already been necessary, as the site of discovery was set out to be flooded to form a reservoir. Consequently, 72 individuals were captured and transferred to another locality.
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
, Thamnophilidae, of passerine
Passerine
A passerine is a bird of the order Passeriformes, which includes more than half of all bird species. Sometimes known as perching birds or, less accurately, as songbirds, the passerines form one of the most diverse terrestrial vertebrate orders: with over 5,000 identified species, it has roughly...
bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s found across subtropical and tropical Central and South America, from Mexico to Argentina. There are more than 200 species, known variously as antshrikes, antwrens, antvireos, fire-eyes, bare-eyes and bushbirds. They are related to the antthrushes and antpittas (family Formicariidae
Formicariidae
The Formicariidae, formicariids, or ground antbirds are a family of smallish passerine birds of subtropical and tropical Central and South America. They are between 10 and 20 cm in length, and are related to the antbirds, Thamnophilidae, and gnateaters, Conopophagidae...
), the tapaculo
Tapaculo
The tapaculos are a group of small suboscine passeriform birds with numerous species, found mainly in South America and with the highest diversity in the Andean regions...
s, the gnateater
Gnateater
The gnateaters are a bird family, Conopophagidae, consisting of ten small passerine species in two genera, which occur in South and Central America...
s and the ovenbirds
Ovenbird (family)
Ovenbirds or furnariids are a large family of small suboscine passerine birds found in Mexico, and Central and South America. They form the family Furnariidae...
. Despite some species' common names, this family is not closely related to the wren
Wren
The wrens are passerine birds in the mainly New World family Troglodytidae. There are approximately 80 species of true wrens in approximately 20 genera....
s, vireo
Vireo
The vireos are a group of small to medium-sized passerine birds restricted to the New World. They are typically dull-plumaged and greenish in color, the smaller species resembling wood warblers apart from their heavier bills...
s or shrike
Shrike
Shrikes are passerine birds of the family Laniidae. The family is composed of thirty-one species in three genera. The family name, and that of the largest genus, Lanius, is derived from the Latin word for "butcher", and some shrikes were also known as "butcher birds" because of their feeding habits...
s.
Antbirds are generally small birds with rounded wings and strong legs. They have mostly sombre grey, white, brown and rufous
Rufous
Rufous is a colour that may be described as reddish-brown or brownish-red, as of rust or oxidised iron.The first recorded use of rufous as a colour name in English was in the year 1782....
plumage
Plumage
Plumage refers both to the layer of feathers that cover a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage vary between species and subspecies and can also vary between different age classes, sexes, and season. Within species there can also be a...
, which is sexually dimorphic
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
in pattern and colouring. Some species communicate warnings to rivals by exposing white feather patches on their backs or shoulders. Most have heavy bills
Beak
The beak, bill or rostrum is an external anatomical structure of birds which is used for eating and for grooming, manipulating objects, killing prey, fighting, probing for food, courtship and feeding young...
, which in many species are hooked at the tip.
Most species live in forests, although a few are found in other habitats. Insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s and other arthropods form the most important part of their diet, although small vertebrates are occasionally taken. Most species feed in the understory
Understory
Understory is the term for the area of a forest which grows at the lowest height level below the forest canopy. Plants in the understory consist of a mixture of seedlings and saplings of canopy trees together with understory shrubs and herbs...
and midstory of the forest, although a few feed in the canopy
Canopy (forest)
In biology, the canopy is the aboveground portion of a plant community or crop, formed by plant crowns.For forests, canopy also refers to the upper layer or habitat zone, formed by mature tree crowns and including other biological organisms .Sometimes the term canopy is used to refer to the extent...
and a few on the ground. Many join mixed-species feeding flocks, and a few species are core members. To various degrees, around eighteen species specialise in following
Ant-follower
Ant-followers are birds that feed by following swarms of army ants and take prey flushed by those ants. The best known ant-followers are 18 species of antbird in the family Thamnophilidae, but other families of birds may follow ants including thrushes, chats, ant-tanagers, cuckoos, and...
columns of army ant
Ecitoninae
Most New World army ants belong to the subfamily Ecitoninae. This subfamily is further broken into two groups in the New World, the tribes Cheliomyrmecini and Ecitonini. The former contains only the genus Cheliomyrmex, and the tribe Ecitonini contains four genera, Neivamyrmex, Nomamyrmex, Labidus,...
s to eat the small invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s flushed by the ants, and many others may feed in this way opportunistically.
Antbirds are monogamous
Monogamy
Monogamy /Gr. μονός+γάμος - one+marriage/ a form of marriage in which an individual has only one spouse at any one time. In current usage monogamy often refers to having one sexual partner irrespective of marriage or reproduction...
, mate for life, and defend territories
Territory (animal)
In ethology the term territory refers to any sociographical area that an animal of a particular species consistently defends against conspecifics...
. They usually lay two eggs in a nest that is either suspended from branches or supported on a branch, stump, or mound on the ground. Both parents share the tasks of incubation
Avian incubation
Incubation refers to the process by which certain oviparous animals hatch their eggs, and to the development of the embryo within the egg. The most vital factor of incubation is the constant temperature required for its development over a specific period. Especially in domestic fowl, the act of...
and of brooding and feeding the nestlings. After fledging
Fledge
Fledge is the stage in a young bird's life when the feathers and wing muscles are sufficiently developed for flight. It also describes the act of a chick's parents raising it to a fully grown state...
, each parent cares exclusively for one chick.
Thirty-eight species are threatened with extinction as a result of human activities. Antbirds are not targeted by either hunters or the pet trade. The principal threat is habitat loss
Habitat destruction
Habitat destruction is the process in which natural habitat is rendered functionally unable to support the species present. In this process, the organisms that previously used the site are displaced or destroyed, reducing biodiversity. Habitat destruction by human activity mainly for the purpose of...
, which causes habitat fragmentation
Habitat fragmentation
Habitat fragmentation as the name implies, describes the emergence of discontinuities in an organism's preferred environment , causing population fragmentation...
and increased nest predation in habitat fragments.
Systematics
The antbird family Thamnophilidae used to be considered a subfamily, Thamnophilinae, within a larger family FormicariidaeFormicariidae
The Formicariidae, formicariids, or ground antbirds are a family of smallish passerine birds of subtropical and tropical Central and South America. They are between 10 and 20 cm in length, and are related to the antbirds, Thamnophilidae, and gnateaters, Conopophagidae...
that included antthrush
Formicariidae
The Formicariidae, formicariids, or ground antbirds are a family of smallish passerine birds of subtropical and tropical Central and South America. They are between 10 and 20 cm in length, and are related to the antbirds, Thamnophilidae, and gnateaters, Conopophagidae...
es and antpitta
Formicariidae
The Formicariidae, formicariids, or ground antbirds are a family of smallish passerine birds of subtropical and tropical Central and South America. They are between 10 and 20 cm in length, and are related to the antbirds, Thamnophilidae, and gnateaters, Conopophagidae...
s. Formerly, that larger family was known as the "antbird family" and the Thamnophilinae were "typical antbirds". In this article, "antbird" and "antbird family" refer to the family Thamnophilidae.
Thamnophilidae was removed from Formicariidae, leaving behind the antthrushes and antpittas, due to recognition of differences in the structure of the breastbone (sternum
Sternum
The sternum or breastbone is a long flat bony plate shaped like a capital "T" located anteriorly to the heart in the center of the thorax...
) and syrinx
Syrinx (biology)
Syrinx is the name for the vocal organ of birds. Located at the base of a bird's trachea, it produces sounds without the vocal cords of mammals. The sound is produced by vibrations of some or all of the membrana tympaniformis and the pessulus caused by air flowing through the syrinx...
, and Sibley and Ahlquist's examination of DNA-DNA hybridisation. The Thamnophilidae antbirds are members of the infraorder Tyrannides (or tracheophone suboscines
Tyranni
The suborder of passerine birds Tyranni includes about 1,000 species, the large majority of which are South American. It is named after the type genus Tyrannus....
), one of two infraorders in the suborder Tyranni. The Thamnophilidae are now thought to occupy a fairly basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
position within the infraorder, i. e. with regard to their relatives the antthrushes and antpittas, tapaculo
Tapaculo
The tapaculos are a group of small suboscine passeriform birds with numerous species, found mainly in South America and with the highest diversity in the Andean regions...
s, gnateater
Gnateater
The gnateaters are a bird family, Conopophagidae, consisting of ten small passerine species in two genera, which occur in South and Central America...
s, and also the ovenbirds
Ovenbird (family)
Ovenbirds or furnariids are a large family of small suboscine passerine birds found in Mexico, and Central and South America. They form the family Furnariidae...
. The sister group of the Thamnophilidae is thought to be the gnateaters. The ovenbirds, tapaculos, antthrushes and antpittas are thought to represent a different radiation of that early split.
The antbird family contains over 200 species, variously called antwrens, antvireos, antbirds and antshrikes. The names refer to the relative sizes of the birds (increasing in the order given, though with exceptions) rather than any particular resemblance to the true wren
Wren
The wrens are passerine birds in the mainly New World family Troglodytidae. There are approximately 80 species of true wrens in approximately 20 genera....
s, vireo
Vireo
The vireos are a group of small to medium-sized passerine birds restricted to the New World. They are typically dull-plumaged and greenish in color, the smaller species resembling wood warblers apart from their heavier bills...
s or shrike
Shrike
Shrikes are passerine birds of the family Laniidae. The family is composed of thirty-one species in three genera. The family name, and that of the largest genus, Lanius, is derived from the Latin word for "butcher", and some shrikes were also known as "butcher birds" because of their feeding habits...
s. In addition, members of the genus Phlegopsis are known as bare-eye
Phlegopsis
Phlegopsis is a genus of bird in the Thamnophilidae family. They are known as "bare-eyes", which is a reference to a colourful bare patch of skin around their eyes. They are restricted to humid forest in the Amazon of South America...
s, Pyriglena as fire-eye
Pyriglena
The fire-eyes, Pyriglena, are a genus of birds in the antbird family Thamnophilidae.The genus contains three species, all found in South America. The fire-eyes are 16–18 cm in length, weigh 25-36 g and have characteristic red eyes that give them their name...
s and Neoctantes and Clytoctantes as bushbird
Clytoctantes
Clytoctantes is a South American genus of bird in the Thamnophilidae family. Males are grey or black and females are mainly rufous. The stubby, hefty bill has a distinctly upcurved lower mandible and a straight culmen , which possibly is a modification for opening bamboo stems in their search for...
s. Although the systematics of the Thamnophilidae is based on studies from the mid-19th century, when fewer than half the present species were known, comparison of the myoglobin
Myoglobin
Myoglobin is an iron- and oxygen-binding protein found in the muscle tissue of vertebrates in general and in almost all mammals. It is related to hemoglobin, which is the iron- and oxygen-binding protein in blood, specifically in the red blood cells. The only time myoglobin is found in the...
intron
Intron
An intron is any nucleotide sequence within a gene that is removed by RNA splicing to generate the final mature RNA product of a gene. The term intron refers to both the DNA sequence within a gene, and the corresponding sequence in RNA transcripts. Sequences that are joined together in the final...
2, GAPDH
Glyceraldehyde 3-phosphate dehydrogenase
Glyceraldehyde 3-phosphate dehydrogenase is an enzyme of ~37kDa that catalyzes the sixth step of glycolysis and thus serves to break down glucose for energy and carbon molecules...
intron 11 and the mtDNA
Mitochondrial DNA
Mitochondrial DNA is the DNA located in organelles called mitochondria, structures within eukaryotic cells that convert the chemical energy from food into a form that cells can use, adenosine triphosphate...
cytochrome b
Cytochrome b
Cytochrome b/b6 is the main subunit of transmembrane cytochrome bc1 and b6f complexes. In addition, it commonly refers to a region of mtDNA used for population genetics and phylogenetics.- Function :...
DNA sequences has largely confirmed it. There are two major clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
s – most antshrikes and other larger, strong-billed species as well as Herpsilochmus
Herpsilochmus
Herpsilochmus is a genus of birds in the antbird family . They are found in forest, woodland and shrub in South America, although a single species also occurs in Panama. All are relatively small antbirds that are sexually dichromatic...
, versus the classical antwrens and other more slender, longer-billed species – and the monophyly
Monophyly
In common cladistic usage, a monophyletic group is a taxon which forms a clade, meaning that it contains all the descendants of the possibly hypothetical closest common ancestor of the members of the group. The term is synonymous with the uncommon term holophyly...
of most genera was confirmed.
The Thamnophilidae contains several large or very large genera
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
and numerous small or monotypic ones. Several, which are difficult to assign, seem to form a third, hitherto unrecognised clade independently derived from ancestral antbirds. The results also confirmed suspicions of previous researchers that some species, most notably in Myrmotherula
Myrmotherula
Myrmotherula is a genus of bird in the Thamnophilidae family. Several species previously included in this genus as the "Stipple-throated group" have now been transferred to a new genus, Epinecrophylla...
and Myrmeciza
Myrmeciza
Myrmeciza is a perching bird genus in the family Thamnophilidae. About 20 species have been placed here in recent times, but thus delimited the "genus" is almost certainly not monophyletic....
, need to be assigned to other genera. Still, due to the difficulties of sampling from such a large number of often poorly known species, the assignment of some genera is still awaiting confirmation.
Morphology
Passerine
A passerine is a bird of the order Passeriformes, which includes more than half of all bird species. Sometimes known as perching birds or, less accurately, as songbirds, the passerines form one of the most diverse terrestrial vertebrate orders: with over 5,000 identified species, it has roughly...
s that range in size from the large Giant Antshrike
Giant Antshrike
The Giant Antshrike is a species of bird in the Thamnophilidae family, belonging to the monotypic genus Batara. It is found in Argentina, Bolivia, Brazil, and Paraguay...
, which measures 45 cm (18 in) and weighs 150 g
Gram
The gram is a metric system unit of mass....
(5.29 oz
Ounce
The ounce is a unit of mass with several definitions, the most commonly used of which are equal to approximately 28 grams. The ounce is used in a number of different systems, including various systems of mass that form part of the imperial and United States customary systems...
), to the tiny 8-cm (3 in) Pygmy Antwren
Pygmy Antwren
The Pygmy Antwren is a species of bird in the Thamnophilidae family, the antbirds.It is found in Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Peru, Suriname, and Venezuela....
, which weighs 7 g (0.25 oz). In general terms, "antshrikes" are relatively large-bodied birds, "antvireos" are medium-sized and chunky, while "antwrens" include most smaller species; "antbird" genuses can vary greatly in size. Members of this family have short rounded wings that provide good manoeuvrability when flying
Bird flight
Flight is the main mode of locomotion used by most of the world's bird species. Flight assists birds while feeding, breeding and avoiding predators....
in dense undergrowth. The legs are large and strong, particularly in species that are obligate ant-follower
Ant-follower
Ant-followers are birds that feed by following swarms of army ants and take prey flushed by those ants. The best known ant-followers are 18 species of antbird in the family Thamnophilidae, but other families of birds may follow ants including thrushes, chats, ant-tanagers, cuckoos, and...
s. These species are well adapted to gripping vertical stems and sapling
Tree
A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...
s, which are more common than horizontal branches in the undergrowth, and thus the ability to grip them is an advantage for birds following swarms of army ants. The claws of these antbirds are longer than those of species that do not follow ants, and the soles of some species have projections that are tough and gripping when the foot is clenched. Tarsus
Tarsus (skeleton)
In tetrapods, the tarsus is a cluster of articulating bones in each foot situated between the lower end of tibia and fibula of the lower leg and the metatarsus. In the foot the tarsus articulates with the bones of the metatarsus, which in turn articulate with the bones of the individual toes...
length in antbirds is related to foraging strategy. Longer tarsi typically occur in genera such as the Thamnophilus
Thamnophilus
Thamnophilus is a genus of antbird in the family Thamnophilidae. The species in this genus are commonly known as antshrikes. They are insectivores that feed by gleaning prey from foliage and are found in the Neotropics....
antshrikes that forage by perch-gleaning
Gleaning (birds)
Gleaning is a term for a feeding strategy by birds in which they catch invertebrate prey, mainly arthropods, by plucking them from foliage or the ground, from crevices such as rock faces and under the eaves of houses, or even, as in the case of ticks and lice, from living animals. This behavior is...
(sitting and leaning forward to snatch insects from the branch), whereas shorter tarsi typically occur in those that catch prey on the wing, such as the Thamnomanes
Thamnomanes
Thamnomanes is a genus of antshrikes in the perching bird family Thamnophilidae. They are restricted to the Neotropics and are important components of forest mixed-species feeding flocks.This genus contains the following species:...
antshrikes.
Most antbirds have proportionately large, heavy bills
Beak
The beak, bill or rostrum is an external anatomical structure of birds which is used for eating and for grooming, manipulating objects, killing prey, fighting, probing for food, courtship and feeding young...
. Several genera of antshrike have a strongly hooked tip to the bill, and all antbirds have a notch or 'tooth' at the tip of the bill which helps in holding and crushing insect prey. The two genera
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of bushbirds have upturned chisel-like bills.
The plumage
Plumage
Plumage refers both to the layer of feathers that cover a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage vary between species and subspecies and can also vary between different age classes, sexes, and season. Within species there can also be a...
of antbirds is soft and not brightly coloured, although it is occasionally striking. The colour palette of most species is blackish shades, whitish shades, rufous, chestnut and brown. Plumages can be uniform in colour or patterned with barring or spots. Sexual dimorphism
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
– differences in plumage colour and pattern between males and females – is common in the family. Overall the pattern within the family is for the males to have combinations of grey, black or white plumage and the females having buff, rufous and brown colours. For example, the male Dot-winged Antwren
Dot-winged Antwren
The Dot-winged Antwren is a passerine bird in the antbird family. In the past it was sometimes known as the Velvety Antwren, and some of its more distinctive subspecies have their own infrequently used English names...
is primarily blackish, whereas the female has rust-coloured underparts. In some genera, such as Myrmotherula, species are better distinguished by female plumage than by male. Many species of antbirds have a contrasting 'patch' of white (sometimes other colours) feathers on the back (known as a interscapular patches), shoulder or underwing. This is usually concealed by the darker feathers on the back but when the bird is excited or alarmed these feathers can be raised to flash the white patch. Dot-winged Antwrens puff out white back patches, whereas in Bluish-slate Antshrike
Bluish-slate Antshrike
The Bluish-slate Antshrike is a species of bird in the Thamnophilidae family.It is found in Bolivia, Brazil, and Peru.Its natural habitat is subtropical or tropical moist lowland forests.-References:...
s and White-flanked Antwren
White-flanked Antwren
The White-flanked Antwren is a passerine bird in the antbird family.-Taxonomy:The subspecies M. a. luctuosa, the Silvery-flanked Antwren, is sometimes split as a full species.-Distribution and habitat:...
s the white patch is on the shoulder.
Voice
The songs and calls of antbirds are generally composed of repeated simple uncomplicated notes. The family is one of the suboscines (suborder TyranniTyranni
The suborder of passerine birds Tyranni includes about 1,000 species, the large majority of which are South American. It is named after the type genus Tyrannus....
) which have simpler syrinxes
Syrinx (biology)
Syrinx is the name for the vocal organ of birds. Located at the base of a bird's trachea, it produces sounds without the vocal cords of mammals. The sound is produced by vibrations of some or all of the membrana tympaniformis and the pessulus caused by air flowing through the syrinx...
("voiceboxes") than other songbirds. Nevertheless their songs are distinctive and species-specific, allowing field identification by ear. Antbirds rely on their calls for communication, as is typical of birds in dark forests. Most species have at least two types of call, the loudsong and the softsong. The functions of many calls have been deduced from their context; for example some loudsongs have a territorial purpose
Territory (animal)
In ethology the term territory refers to any sociographical area that an animal of a particular species consistently defends against conspecifics...
and are given when birds meet at the edges of their territories, or during the morning rounds of the territory. Pairs in neighbouring territories judge the proximity of rivals by the degradation of the song caused by interference by the environment. In bouts of territorial defence the male will face off with the other male and the female with her counterpart. Loudsong duets are also potentially related to the maintenance of pair bonds. The functions of softsongs are more complex, and possibly related to pair-bond maintenance. In addition to these two main calls a range of other sounds are made; these include scolding in mobbing of predators. The calls of antbirds are also used interspecifically. Some species of antbirds and even other birds will actively seek out ant-swarms using the calls of some species of ant-followers as clues.
Distribution and habitat
Barred Antshrike
The Barred Antshrike, Thamnophilus doliatus, is a passerine bird in the antbird family. It is found in the Neotropics from Tamaulipas, Mexico, through Central America, Trinidad and Tobago, and a large part of South America east of the Andes as far south as northern Argentina, Bolivia and Paraguay....
, have a continental distribution that spans most of the South and Middle American
Middle America (Americas)
Middle America is a region in the mid-latitudes of the Americas. In southern North America, it usually comprises Mexico, the nations of Central America, and the West Indies. The scope of the term may vary...
distribution of the family; others, such as the Ash-throated Antwren
Ash-throated Antwren
The Ash-throated Antwren is a bird in the Antbird family, described as new to science in 1986.The first specimens were collected in northern Peru in 1983....
, have a tiny distribution.
Antbirds are mostly birds of humid lowland rainforest
Rainforest
Rainforests are forests characterized by high rainfall, with definitions based on a minimum normal annual rainfall of 1750-2000 mm...
s. Few species are found at higher elevations, with less than 10% of species having ranges above 2000 m (6500 ft) and almost none with ranges above 3000 m (10000 ft). The highest species diversity is found in the Amazon Basin
Amazon Basin
The Amazon Basin is the part of South America drained by the Amazon River and its tributaries that drains an area of about , or roughly 40 percent of South America. The basin is located in the countries of Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru, and Venezuela...
, with up to 45 species being found in single locations in sites across Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
, Colombia
Colombia
Colombia, officially the Republic of Colombia , is a unitary constitutional republic comprising thirty-two departments. The country is located in northwestern South America, bordered to the east by Venezuela and Brazil; to the south by Ecuador and Peru; to the north by the Caribbean Sea; to the...
, Bolivia
Bolivia
Bolivia officially known as Plurinational State of Bolivia , is a landlocked country in central South America. It is the poorest country in South America...
and Peru
Peru
Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....
. The number of species drops dramatically towards the further reaches of the family's range; there are only seven species in Mexico, for example. Areas of lower thamnophilid diversity may contain localised endemics, however. The Yapacana Antbird
Yapacana Antbird
The Yapacana Antbird is a species of bird in the Thamnophilidae family. It is found in Brazil, Colombia, and Venezuela.Its natural habitat is subtropical or tropical moist lowland forests.-References:...
, for example, is restricted to the stunted woodlands that grow in areas of nutrient-poor white-sand soil
Soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...
(the so-called Amazonian caatinga
Caatinga
Caatinga is a type of vegetation, and an ecoregion characterized by this vegetation in the northeastern part of Brazil. The name "Caatinga" is a Tupi word meaning "white forest" or "white vegetation"...
) in Brazil, Venezuela and Colombia. Some species are predominantly associated with microhabitats within a greater ecosystem; for example, the Bamboo Antshrike
Bamboo Antshrike
The Bamboo Antshrike is a species of bird in the Thamnophilidae family.It is found in Bolivia, Brazil, and Peru.Its natural habitat is subtropical or tropical moist lowland forests.-References:...
is predominantly found in bamboo patches.
Behaviour
Antbirds are diurnal: they feed, breed and defend territories during the day. Many of the family are, however, reluctant to enter areas of direct sunlight where it breaks through the forest canopy. Antbirds will engage in antingAnting (bird activity)
In the behavior called anting, birds rub insects on their feathers, usually ants, which secrete liquids containing chemicals such as formic acid, that can act as an insecticide, miticide, fungicide, bactericide, or to make them edible by removing the distasteful acid. It possibly also supplements...
, a behaviour in which ants (or other arthropods) are rubbed on the feathers before being discarded or eaten. While this has conventionally been considered a way to remove and control feather parasite
Parasitism
Parasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred to organisms with lifestages that needed more than one host . These are now called macroparasites...
s, it has been suggested that for antbirds it may simply be a way to deal with the distasteful substances in prey items.
Feeding
Arthropod
An arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...
s. These are mostly insects, including grasshoppers and crickets, cockroaches, praying mantises, stick insects and the larvae of butterflies and moths. In addition antbirds often take spiders, scorpions and centipedes. They swallow smaller prey items quickly, whereas they often beat larger items against branches in order to remove wings and spines. Larger species can kill and consume frog
Frog
Frogs are amphibians in the order Anura , formerly referred to as Salientia . Most frogs are characterized by a short body, webbed digits , protruding eyes and the absence of a tail...
s and lizard
Lizard
Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...
s as well, but generally these do not form an important part of the diet of this family. Other food items may also be eaten, including fruit, eggs and slugs.
The family uses a number of techniques to obtain prey. The majority of antbirds are arboreal
Arboreal locomotion
Arboreal locomotion is the locomotion of animals in trees. In every habitat in which trees are present, animals have evolved to move in them. Some animals may only scale trees occasionally, while others are exclusively arboreal. These habitats pose numerous mechanical challenges to animals...
, with most of those feeding in the understory
Understory
Understory is the term for the area of a forest which grows at the lowest height level below the forest canopy. Plants in the understory consist of a mixture of seedlings and saplings of canopy trees together with understory shrubs and herbs...
, many in the middle story and some in the canopy
Canopy (forest)
In biology, the canopy is the aboveground portion of a plant community or crop, formed by plant crowns.For forests, canopy also refers to the upper layer or habitat zone, formed by mature tree crowns and including other biological organisms .Sometimes the term canopy is used to refer to the extent...
. A few species feed in the leaf litter
Plant litter
Plant litter, leaf litter or tree litter is dead plant material, such as leaves, bark, needles, and twigs, that has fallen to the ground. Litter provides habitat for small animals, fungi, and plants, and the material may be used to construct nests. As litter decomposes, nutrients are released to...
; for example, the Wing-banded Antbird
Wing-banded Antbird
The Wing-banded Antbird is a species of bird in the Thamnophilidae family. It is placed in the monotypic genus Myrmornis....
forages in areas of dense leaf-litter. It does not use its feet to scratch the leaf litter, as do some other birds; instead it uses its long bill to turn over leaves rapidly (never picking them up). The antbirds that forage arboreally show a number of techniques and specialisations. Some species perch-glean
Gleaning (birds)
Gleaning is a term for a feeding strategy by birds in which they catch invertebrate prey, mainly arthropods, by plucking them from foliage or the ground, from crevices such as rock faces and under the eaves of houses, or even, as in the case of ticks and lice, from living animals. This behavior is...
, perching on a branch watching for prey and snatching it by reaching forward, where others sally
Hawking (birds)
Hawking is a feeding strategy in birds involving catching flying insects in the air. The term usually refers to a technique of sallying out from a perch to snatch an insect and then returning to the same or a different perch...
from a perch and snatch prey on the wing. In both cases birds will hop through the foliage or undergrowth and pause, scanning for prey, before pouncing or moving on. The time paused varies, although smaller species tend to be more active and pause for shorter times.
Mixed-species feeding flocks
Conspecificity
Conspecificity is a concept in biology. Two or more individual organisms, populations, or taxa are conspecific if they belong to the same species....
s (members of the same species) and are found in almost all flocks; these are joined by "attendant species". Loud and distinctive calls and conspicuous plumage
Plumage
Plumage refers both to the layer of feathers that cover a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage vary between species and subspecies and can also vary between different age classes, sexes, and season. Within species there can also be a...
are important attributes of nuclear species as they promote cohesion in the flock. The composition of these flocks varies geographically; in Amazonia species of Thamnomanes
Thamnomanes
Thamnomanes is a genus of antshrikes in the perching bird family Thamnophilidae. They are restricted to the Neotropics and are important components of forest mixed-species feeding flocks.This genus contains the following species:...
antshrike are the leading nuclear species; elsewhere other species, such as the Dot-winged Antwren
Dot-winged Antwren
The Dot-winged Antwren is a passerine bird in the antbird family. In the past it was sometimes known as the Velvety Antwren, and some of its more distinctive subspecies have their own infrequently used English names...
s and Checker-throated Antwren
Checker-throated Antwren
The Checker-throated Antwren or Fulvous-bellied Antwren is a small passerine bird in the antbird family. It has traditionally been placed in the genus Myrmotherula, but is, together with other members of the so-called "stipple-throated group", now placed in the new genus Epinecrophylla...
s, fill this role. Other species of antwren and antbird join them along with woodcreeper
Woodcreeper
The woodcreepers comprise a subfamily of sub-oscine passerine birds endemic to the Neotropics. They have traditionally been considered a distinct family Dendrocolaptidae, but most authorities now place them as a subfamily of the ovenbirds...
s, ant-tanagers, foliage-gleaner
Ovenbird (family)
Ovenbirds or furnariids are a large family of small suboscine passerine birds found in Mexico, and Central and South America. They form the family Furnariidae...
s and greenlet
Hylophilus
Hylophilus is a genus of bird in the Vireonidae family.It contains the following species:* Gray-eyed Greenlet * Golden-fronted Greenlet * Brown-headed Greenlet...
s. The benefits of the mixed flock are thought to be related to predation
Predation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...
, since many eyes are better for spotting predatory hawks and falcons. Comparisons between multi-species feeding flocks in different parts of the world found that instances of flocking were positively correlated with predation risk by raptors. For example, where Thamnomanes antshrikes lead the group they give loud warning calls in the presence of predators. These calls are understood and reacted to by all the other species in the flock. The advantage to the Thamnomanes antshrikes is in allowing the rest of the flock, which are typically gleaners, to act as beaters, flushing prey while foraging which the antshrikes can obtain by sallying. Similar roles are filled in other flocks by other antbird species or other bird families, for example the shrike-tanager
Lanio
Lanio is the genus of shrike-tanagers.-Species list:* Fulvous Shrike-tanager, Lanio fulvus* White-winged Shrike-tanager, Lanio versicolor* Black-throated Shrike-tanager, Lanio aurantius...
s. Within the feeding flocks competition
Competition (biology)
Competition is an interaction between organisms or species, in which the fitness of one is lowered by the presence of another. Limited supply of at least one resource used by both is required. Competition both within and between species is an important topic in ecology, especially community ecology...
is reduced by microniche partitioning
Niche differentiation
The term niche differentiation , as it applies to the field of ecology, refers to the process by which natural selection drives competing species into different patterns of resource use or different niches...
; where Dot-winged Antwrens, Checker-throated Antwrens and White-flanked Antwren
White-flanked Antwren
The White-flanked Antwren is a passerine bird in the antbird family.-Taxonomy:The subspecies M. a. luctuosa, the Silvery-flanked Antwren, is sometimes split as a full species.-Distribution and habitat:...
s feed in flocks together, the Dot-wings feed in the densest vines, the White-flank in less dense vegetation, and the Checker-throats in the same density as the latter but in dead foliage only.
Ant-followers
Ecitoninae
Most New World army ants belong to the subfamily Ecitoninae. This subfamily is further broken into two groups in the New World, the tribes Cheliomyrmecini and Ecitonini. The former contains only the genus Cheliomyrmex, and the tribe Ecitonini contains four genera, Neivamyrmex, Nomamyrmex, Labidus,...
s are an important resource used by some species of antbird, and the one from which the family's common name is derived. Many species of tropical ant
Ant
Ants are social insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from wasp-like ancestors in the mid-Cretaceous period between 110 and 130 million years ago and diversified after the rise of flowering plants. More than...
form large raiding swarms, but the swarms are often nocturnal or raid underground. While birds visit these swarms when they occur, the species most commonly attended by birds is the Neotropical species Eciton burchellii
Eciton burchellii
Eciton burchellii is the predominant species of the genus Eciton and a type of New World army ant. Distinct in its expansive, highly organized swarm raids, it is often considered the archetypal species of "army ant" — so much that the term has become its common name — and remains one of...
, which is both diurnal and surface-raiding. It was once thought that attending birds were actually eating the ants, but numerous studies in various parts of E. burchellii's range has shown that the ants act as beaters, flushing insects, other arthropods and small vertebrates into the waiting flocks of "ant-followers". The improvement in foraging efficiency can be dramatic; a study of Spotted Antbird
Spotted Antbird
The Spotted Antbird is a species of bird in the Thamnophilidae family.In southern Central America, it is found in Nicaragua, Costa Rica and Panama; also Colombia and Ecuador of northwestern South America....
s found that they made attempts at prey every 111.8 seconds away from ants, but at swarms they made attempts every 32.3 seconds. While many species of antbirds (and other families) may opportunistically feed at army ant swarms, 18 species of antbird are obligate ant-followers, obtaining most of their diet from swarms. With only three exceptions, these species never regularly forage away from ant swarms. A further four species regularly attend swarms but are as often seen away from them. Obligate ant-followers visit the nesting bivouacs of army ants in the morning to check for raiding activities; other species do not. These species tend to arrive at swarms first, and their calls are used by other species to locate swarming ants.
Because army ants are unpredictable in their movements, it is impractical for obligate ant-followers to maintain a territory
Territory (animal)
In ethology the term territory refers to any sociographical area that an animal of a particular species consistently defends against conspecifics...
that always contains swarms to feed around. Antbirds have evolved
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
a more complicated system than the strict territoriality of most other birds. They generally (details vary among species) maintain breeding territories but travel outside those territories in order to feed at swarms. Several pairs of the same species may attend a swarm, with the dominant pair at the swarm being the pair which holds the territory that the swarm is in. In addition to competition within species, competition among species exists, and larger species are dominant. In its range, the Ocellated Antbird
Ocellated Antbird
The Ocellated Antbird is a species of antbird in the family Thamnophilidae. It is monotypic within the genus Phaenostictus.It is found in Colombia, Costa Rica, Ecuador, Honduras, Nicaragua, and Panama....
is the largest of the obligate ant-following antbirds and is dominant over other members of the family, although it is subordinate to various species from other families (including certain woodcreeper
Woodcreeper
The woodcreepers comprise a subfamily of sub-oscine passerine birds endemic to the Neotropics. They have traditionally been considered a distinct family Dendrocolaptidae, but most authorities now place them as a subfamily of the ovenbirds...
s, motmot
Motmot
The motmots or Momotidae are a family of birds in the near passerine order Coraciiformes, which also includes the kingfishers, bee-eaters and rollers. All extant motmots are restricted to woodland or forest in the Neotropics, and the largest diversity is in Middle America. They have a colourful...
s and the Rufous-vented Ground Cuckoo). At a swarm, the dominant species occupies positions above the central front of the swarm, which yields the largest amount of prey. Smaller, less dominant species locate themselves further away from the centre, or higher above the location of the dominant species, where prey is less plentiful.
Breeding
Antbirds are monogamousMonogamy
Monogamy /Gr. μονός+γάμος - one+marriage/ a form of marriage in which an individual has only one spouse at any one time. In current usage monogamy often refers to having one sexual partner irrespective of marriage or reproduction...
, in almost all cases forming pair bond
Pair bond
In biology, a pair bond is the strong affinity that develops in some species between the males and females in a pair, potentially leading to breeding. Pair-bonding is a term coined in the 1940s that is frequently used in sociobiology and evolutionary psychology circles...
s that last the life of the pair. Studies of the Dusky Antbird
Dusky Antbird
The Dusky Antbird or Tyrannine Antbird, Cercomacra tyrannina, is a passerine bird in the antbird family. It is a resident breeder in tropical Central and South America from southeastern Mexico southwards to western Ecuador, and Amazonian Brazil....
and the White-bellied Antbird
White-bellied Antbird
The White-bellied Antbird , is a passerine bird which breeds in the tropical New World from Panama to northern Brazil and in Trinidad. It is also called Swainson's Antcatcher after William John Swainson, who first described it scientifically...
did not find "infidelity". In the White-plumed Antbird
White-plumed Antbird
The White-plumed Antbird is a species of insectivorous bird in the Thamnophilidae family. It is marked by deep red-brownish plumage, black wings, and a black head with a bright-white feathered mask....
divorces between pairs are common, but, as far as known, this species is exceptional. In most species the pair defends a classic territory
Territory (animal)
In ethology the term territory refers to any sociographical area that an animal of a particular species consistently defends against conspecifics...
, although the nesting territories of ant-followers are slightly different (see feeding above). Territories vary in size from as small as 0.5 ha for the Manu Antbird
Manu Antbird
The Manu Antbird is a species of bird in the Thamnophilidae family.It is found in Bolivia, Brazil, and Peru.Its natural habitat is subtropical or tropical moist lowland forests.-References:...
, to 1500 m (5000 ft) in diameter for the Ocellated Antbird. Ocellated Antbirds have an unusual social system where the breeding pair forms the nucleus of a group or clan that includes their male offspring and their mates. These clans, which can number up to eight birds, work together to defend territories against rivals. Pair bonds are formed with courtship feeding, where the male presents food items to the female. In Spotted Antbirds males may actually feed females sufficiently for the female to cease feeding herself, although she will resume feeding once copulation has occurred. Mutual grooming also plays a role in courtship in some species.
Ocellated Antbird
The Ocellated Antbird is a species of antbird in the family Thamnophilidae. It is monotypic within the genus Phaenostictus.It is found in Colombia, Costa Rica, Ecuador, Honduras, Nicaragua, and Panama....
was first described in 2004. Nests
Bird nest
A bird nest is the spot in which a bird lays and incubates its eggs and raises its young. Although the term popularly refers to a specific structure made by the bird itself—such as the grassy cup nest of the American Robin or Eurasian Blackbird, or the elaborately woven hanging nest of the...
are constructed by both parents, although the male undertakes more of the work in some species. Antbird nests are cups of vegetation such as twigs, dead leaves and plant fibre, and they follow two basic patterns: either suspended or supported. Suspended cups, which may hang from forks in branches, or between two branches, are the more common style of nest. Supported nests rest upon branches, amongst vines, in hollows, and sometimes on mounds of vegetation on the ground. Each species nests at the level where it forages, so a midstory species would build its nest in the midstory. Closely related species nest in the same ways. For example antvireos in the genus Dysithamnus
Dysithamnus
Dysithamnus is a genus of bird in the Thamnophilidae family. Species in this genus are known as antvireos.It contains the following species:* Spot-breasted Antvireo, Dysithamnus stictothorax* Plain Antvireo, Dysithamnus mentalis...
are all suspension nesters.
Avian incubation
Incubation refers to the process by which certain oviparous animals hatch their eggs, and to the development of the embryo within the egg. The most vital factor of incubation is the constant temperature required for its development over a specific period. Especially in domestic fowl, the act of...
, although only the female incubates at night. The length of time taken for chicks to hatch is 14–16 days in most species, although some, such as the Dusky Antbird
Dusky Antbird
The Dusky Antbird or Tyrannine Antbird, Cercomacra tyrannina, is a passerine bird in the antbird family. It is a resident breeder in tropical Central and South America from southeastern Mexico southwards to western Ecuador, and Amazonian Brazil....
, can take as long as 20 days. The altricial
Altricial
Altricial, meaning "requiring nourishment", refers to a pattern of growth and development in organisms which are incapable of moving around on their own soon after hatching or being born...
chicks are born naked and blind. Both parents brood the young until they are able to thermoregulate
Thermoregulation
Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different...
, although, as with incubation, only the female broods at night. In common with many songbirds, the parents take faecal sacs for disposal away from the nest. Both parents feed the chicks, often bringing large prey items. When the chicks reach fledging
Fledge
Fledge is the stage in a young bird's life when the feathers and wing muscles are sufficiently developed for flight. It also describes the act of a chick's parents raising it to a fully grown state...
age, after 8–15 days, attending parents call their chicks. As each chick leaves the nest it is cared for exclusively from then on by the parent that was present then. After the first chick fledges and leaves with a parent the remaining parent may increase the supply of food to speed up the process of fledging. After fledging, chicks spend the first few days well hidden as the parents bring them food. Chicks of some species may not become independent of the parents for as long as four months in some antwrens, but two months is more typical for the rest of the family.
Ecology
Antbirds are common components of the avifauna of some parts of the Neotropics and are thought to be important in some ecological processesEcology
Ecology is the scientific study of the relations that living organisms have with respect to each other and their natural environment. Variables of interest to ecologists include the composition, distribution, amount , number, and changing states of organisms within and among ecosystems...
. They are preyed upon by birds of prey
Bird of prey
Birds of prey are birds that hunt for food primarily on the wing, using their keen senses, especially vision. They are defined as birds that primarily hunt vertebrates, including other birds. Their talons and beaks tend to be relatively large, powerful and adapted for tearing and/or piercing flesh....
, and their tendency to join flocks is thought to provide protection against such predation. The Greater Round-eared Bat
Greater Round-eared Bat
The Greater Round-eared Bat, Tonatia bidens, is a bat species from South America. It is found in northeastern and southern Brazil, northern Argentina, Paraguay and Bolivia. The species feeds on fruit as well as hunting small birds. Once caught birds are taken to a shelter and consumed.-References:*...
preys on some antbird species, such as the White-bibbed Antbird
White-bibbed Antbird
The White-bibbed Antbird is a species of bird in the Thamnophilidae family. It is endemic to Brazil.Its natural habitats are subtropical or tropical moist lowland forests and subtropical or tropical moist montane forests....
and the Scaled Antbird
Scaled Antbird
The Scaled Antbird is a species of bird in the Thamnophilidae family.It is endemic to Brazil.Its natural habitats are subtropical or tropical moist lowland forests and heavily degraded former forest.-References:...
; the latter is the bat's preferred prey. Nests, including incubating adults, chicks and eggs, are vulnerable to predators, particularly snake
Snake
Snakes are elongate, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales...
s but also nocturnal mammals. Nesting success is low for many species, particularly in areas of fragmented habitat.
It was once suggested that the relationship between the obligate and regular ant-followers and the army ants, particularly Eciton burchellii, was mutualistic, with the ants benefiting by having the birds chase prey back down towards them. However, experiments where ant-followers were excluded have shown that the foraging success of the army ants was 30% lower when the birds were present, suggesting that the birds' relationship was in fact parasitic
Parasitism
Parasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred to organisms with lifestages that needed more than one host . These are now called macroparasites...
. This has resulted in a number of behaviours by the ants in order to reduce kleptoparasitism
Kleptoparasitism
Kleptoparasitism or cleptoparasitism is a form of feeding in which one animal takes prey or other food from another that has caught, collected, or otherwise prepared the food, including stored food...
, including hiding of secured prey in the leaf litter and caching of food on trails. It has been suggested that the depressive effect of this parasitism slows the development of E. burchellii swarms and in turn benefits other ant species which are preyed upon by army ants. The ant-following antbirds are themselves followed by three species of butterfly
Butterfly
A butterfly is a mainly day-flying insect of the order Lepidoptera, which includes the butterflies and moths. Like other holometabolous insects, the butterfly's life cycle consists of four parts: egg, larva, pupa and adult. Most species are diurnal. Butterflies have large, often brightly coloured...
in the family Ithomiinae
Ithomiini
Ithomiini is a butterfly tribe in the nymphalid subfamily Danainae. Some authors consider the group to be a subfamily . These butterflies are exclusively Neotropical, found in humid forests from sea-level to 3000 m, from the southwestern United States to Argentina...
which feed on their droppings
Guano
Guano is the excrement of seabirds, cave dwelling bats, and seals. Guano manure is an effective fertilizer due to its high levels of phosphorus and nitrogen and also its lack of odor. It was an important source of nitrates for gunpowder...
. Bird droppings are usually an unpredictable resource in a rainforest, but the regular behaviour of ant-followers makes the exploitation of this resource possible.
Status and conservation
Near Threatened
Near Threatened is a conservation status assigned to species or lower taxa that may be considered threatened with extinction in the near future, although it does not currently qualify for the threatened status...
or worse and therefore at risk of extinction
Extinction
In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...
. Antbirds are neither targeted by the pet trade nor large enough to be hunted; the principal cause of the decline in antbird species is habitat loss
Habitat destruction
Habitat destruction is the process in which natural habitat is rendered functionally unable to support the species present. In this process, the organisms that previously used the site are displaced or destroyed, reducing biodiversity. Habitat destruction by human activity mainly for the purpose of...
. The destruction or modification of forests has several effects on different species of antbirds. The fragmentation of forests into smaller patches affects species that are averse to crossing gaps as small as roads. If these species become locally extinct in a fragment, this reluctance to cross unforested barriers makes their re-establishment unlikely. Smaller forest fragments are unable to sustain mixed-species feeding flocks, leading to local extinctions. Another risk faced by antbirds in fragmented habitat is increased nest
Bird nest
A bird nest is the spot in which a bird lays and incubates its eggs and raises its young. Although the term popularly refers to a specific structure made by the bird itself—such as the grassy cup nest of the American Robin or Eurasian Blackbird, or the elaborately woven hanging nest of the...
predation. An unplanned experiment in fragmentation occurred on Barro Colorado Island
Barro Colorado Island
Barro Colorado Island is located in the man-made Gatun Lake in the middle of the Panama Canal. The island was formed when the waters of the Chagres River were dammed to form the lake. When the waters rose, they covered a significant part of the existing rainforest, and the hilltops remained as...
, a former hill in Panama
Panama
Panama , officially the Republic of Panama , is the southernmost country of Central America. Situated on the isthmus connecting North and South America, it is bordered by Costa Rica to the northwest, Colombia to the southeast, the Caribbean Sea to the north and the Pacific Ocean to the south. The...
that became an isolated island during the flooding caused by the creation of the Panama Canal
Panama Canal
The Panama Canal is a ship canal in Panama that joins the Atlantic Ocean and the Pacific Ocean and is a key conduit for international maritime trade. Built from 1904 to 1914, the canal has seen annual traffic rise from about 1,000 ships early on to 14,702 vessels measuring a total of 309.6...
. Numerous species of antbird formerly resident in the area were extirpated
Local extinction
Local extinction, also known as extirpation, is the condition of a species which ceases to exist in the chosen geographic area of study, though it still exists elsewhere...
, in no small part due to increased levels of nest predation on the island. While the species lost from Barro Colorado are not globally threatened, they illustrate the vulnerability of species in fragmented habitats and help explain the declines of some species. The majority of threatened species have very small natural ranges. Some are also extremely poorly known; for example the Rio de Janeiro Antwren
Rio de Janeiro Antwren
The Rio de Janeiro Antwren is a species of bird in the Thamnophilidae family.It is endemic to Brazil, and is currently thought only to survive in Guapi Açu Ecological Reserve, although identification is tricky and its continued survival has been questioned.Its natural habitat is subtropical or...
is known only from a single specimen
Specimen
A specimen is a portion/quantity of material for use in testing, examination, or study.BiologyA laboratory specimen is an individual animal, part of an animal, a plant, part of a plant, or a microorganism, used as a representative to study the properties of the whole population of that species or...
collected in 1982, although there have been unconfirmed reports since 1994 and it is currently listed as critically endangered
Critically Endangered
Critically Endangered is the highest risk category assigned by the IUCN Red List for wild species. Critically Endangered means that a species' numbers have decreased, or will decrease, by 80% within three generations....
. Additionally, new species are discovered at regular intervals; the Caatinga Antwren
Caatinga Antwren
The Caatinga Antwren is a species of bird in the Thamnophilidae family.It is endemic to Brazil.Its natural habitats are subtropical or tropical dry forests and dry savanna.It is threatened by habitat loss.-References:...
was described in 2000, the Acre Antshrike
Acre Antshrike
The Acre Antshrike is a member of the antbird family . Its closest relatives are the Streak-backed Antshrike and the Amazonian Antshrike ....
in 2004, the Sincorá Antwren
Sincorá Antwren
The Sincorá Antwren is a small passerine bird of the genus Formicivora in the family Thamnophilidae, the typical antbirds. It is endemic to a small area of eastern Brazil. The bird was not described as a new species until 2007...
in 2007, and the description of a relative of the Paraná Antwren
Marsh Antwren
The Marsh Antwren , also known as the Paraná Antwren, is a species of bird in the Thamnophilidae family. It is monotypic within the genus Stymphalornis, but possibly better included in Formicivora. It is endemic to marshes and swamps in the Brazilian states of Paraná and Santa Catarina...
discovered in 2005 in the outskirts of São Paulo
São Paulo
São Paulo is the largest city in Brazil, the largest city in the southern hemisphere and South America, and the world's seventh largest city by population. The metropolis is anchor to the São Paulo metropolitan area, ranked as the second-most populous metropolitan area in the Americas and among...
is being prepared. While not yet scientifically described, conservation efforts have already been necessary, as the site of discovery was set out to be flooded to form a reservoir. Consequently, 72 individuals were captured and transferred to another locality.
External links
- Antbird videos and photos on the Internet Bird Collection
- Xeno-Canto: Antbird sounds