Tropical Gnatcatcher
Encyclopedia
The Tropical Gnatcatcher (Polioptila plumbea) is a small active insectivorous songbird
, which is a resident species throughout a large part of the Neotropics. There are large geographical variations in its voice and plumage
, resulting in some populations sometimes being considered separate species, notably the bilineata group as the White-browed Gnatcatcher, and the taxon
maior as the Marañón Gnatcatcher.
" is similar to that of other gnatcatchers
; a small bird with a relatively long thin bill, a long frequently cocked tail, grey upperparts and whitish underparts. The central rectrices are black, while the outer are white (consequently, the tail appears primarily black from above, white from below), and there is a white patch in the wing (caused by broad white edging to the tertials). Males of the nominate group have a contrasting black cap that reaches just below the eye, while this is lacking in females, which instead have a grey cap (same colour as back). Some females have an irregular black post-ocular patch. This is especially prominent in female of the subspecies atricapilla from north-eastern Brazil
.
Males of the White-browed Gnatcatcher (bilineata group) resemble males of the nominate group, but the white of their underparts extends clearly above the eye, resulting in a more restricted black cap, which, however, often is connected with a fine black line from the nape to the rear of the eye. Females resemble males, but with the black of the cap replaced by grey, except for an irregulat black patch in the post-ocular region (lacking in some females). As the white in both sexes extends above the eye, they appear rather "white-browed" (unlike the nominate group), resulting in the common name
proposed for this group if considered a separate species.
The final group, which only includes the taxon
maior (the so-called Marañón Gnatcatcher), is distinctive. Males resemble males of the nominate group, but, except for their white forecrown, females resemble males of the bilineata group. Juveniles
of all groups resemble females.
The Tropical Gnatcatcher has a thin buzzy gezzz call and a trilled swee see see si si si su su song. However, exact structure and tone of the voice varies greatly over its range.
region), west through the Amazon Basin
, and north to the Guianas, northern Venezuela
and northern Colombia (including the valleys of Magdalena
and Cauca
). The bilineata group is found from north-western Peru
, through the Chocó and Central America
, to southern Mexico
. The Marañón Gnatcatcher is restricted to the Marañón
valley in northern Peru
.
Both the nominate and the bilineata group are found in a wide range of wooded habitats, ranging from the arid woodland and scrub (such as the Caatinga
in Brazil) to humid forest (such as the various types of humid forest in the Amazon). They are mainly found in lowlands below an altitude of 1,000 m (3,300 ft), but the taxon maior, which is restricted to dry woodland and scrub, is found at altitudes of 200-2,700 m (650-8,850 ft).
In dense humid forest, it is typically found at canopy
height, but it is commonly seen a lower levels in more open habitats. The Tropical Gnatcatcher gleans spider
s and their eggs, beetle
s, caterpillar
s and other insect
s from outer twigs and foliage. Moving about alone or in pairs, it often joins mixed-species feeding flock
s with tanager
s, New World warbler
s and honeycreeper
s.
The nest is a small cup like that of a hummingbird
, constructed from vegetable fibres 6.5 – 28 ft (2–8 m) high on a tree branch. The female lays two or three brown-spotted white eggs in May and June.
This is a curious bird and unafraid of humans; this behavior renders it vulnerable to predators however. Even omnivorous mammal
s as small as the Common Marmoset
(Callithrix jacchus) will eagerly plunder Tropical Gnatcatcher nests in the undergrowth – perhaps more often during the dry season
when fruits are scarce – despite the birds' attempts to defend their offspring.
by BirdLife International
and IUCN. In the Amazon, this species is primarily associated with relatively open habitats (e.g. Várzea Forest), resulting in it being rather local. It may benefit from the opening of the forest caused by deforestation
, at least as long as some stands of trees remain. The Marañón Gnatcatcher remains common, but is restricted to a small region with extensive habitat destruction
. Three other taxa with highly restricted distributions may be threatened, these being anteocularis of the Magdalena Valley (Colombia), daguae of the Cauca Valley (Colombia), and cinericia of Coiba Island (Panama
).
Songbird
A songbird is a bird belonging to the suborder Passeri of the perching birds . Another name that is sometimes seen as scientific or vernacular name is Oscines, from Latin oscen, "a songbird"...
, which is a resident species throughout a large part of the Neotropics. There are large geographical variations in its voice and 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...
, resulting in some populations sometimes being considered separate species, notably the bilineata group as the White-browed Gnatcatcher, and the taxon
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...
maior as the Marañón Gnatcatcher.
Description
The adult Tropical Gnatcatcher is 10–12 cm (4-5 in) long, and weighs 6–8 g (0.2-0.3 oz). Its "jizzJizz (birding)
Jizz is a term used by birders to describe the overall impression or appearance of a bird garnered from such features as shape, posture, flying style or other habitual movements, size and colouration combined with voice, habitat and location....
" is similar to that of other gnatcatchers
Polioptila
Polioptila is a genus of bird in the Polioptilidae family.It contains the following species:* Blue-gray Gnatcatcher, Polioptila caerulea* Cuban Gnatcatcher, Polioptila lembeyei* California Gnatcatcher, Polioptila californica...
; a small bird with a relatively long thin bill, a long frequently cocked tail, grey upperparts and whitish underparts. The central rectrices are black, while the outer are white (consequently, the tail appears primarily black from above, white from below), and there is a white patch in the wing (caused by broad white edging to the tertials). Males of the nominate group have a contrasting black cap that reaches just below the eye, while this is lacking in females, which instead have a grey cap (same colour as back). Some females have an irregular black post-ocular patch. This is especially prominent in female of the subspecies atricapilla from north-eastern 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...
.
Males of the White-browed Gnatcatcher (bilineata group) resemble males of the nominate group, but the white of their underparts extends clearly above the eye, resulting in a more restricted black cap, which, however, often is connected with a fine black line from the nape to the rear of the eye. Females resemble males, but with the black of the cap replaced by grey, except for an irregulat black patch in the post-ocular region (lacking in some females). As the white in both sexes extends above the eye, they appear rather "white-browed" (unlike the nominate group), resulting in the common name
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
proposed for this group if considered a separate species.
The final group, which only includes the taxon
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...
maior (the so-called Marañón Gnatcatcher), is distinctive. Males resemble males of the nominate group, but, except for their white forecrown, females resemble males of the bilineata group. Juveniles
Juvenile (organism)
A juvenile is an individual organism that has not yet reached its adult form, sexual maturity or size. Juveniles sometimes look very different from the adult form, particularly in terms of their colour...
of all groups resemble females.
The Tropical Gnatcatcher has a thin buzzy gezzz call and a trilled swee see see si si si su su song. However, exact structure and tone of the voice varies greatly over its range.
Distribution and ecology
The nominate group if found from north-eastern Brazil (the CaatingaCaatinga
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"...
region), west through 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...
, and north to the Guianas, northern Venezuela
Venezuela
Venezuela , officially called the Bolivarian Republic of Venezuela , is a tropical country on the northern coast of South America. It borders Colombia to the west, Guyana to the east, and Brazil to the south...
and northern Colombia (including the valleys of Magdalena
Magdalena River Valley
The Magdalena River Valley is a valley in Colombia located within the Colombian Andes mountain ranges. The valley is specifically located between the Cordillera Central and Cordillera Oriental and crossed by the river of the same name, the Magdalena River....
and Cauca
Cauca River
The Cauca River is a river in Colombia that lies between the Occidental and Central cordilleras. Born in southwestern Colombia near the city of Popayán, it joins the Magdalena River near Pinillos in Bolívar Department, and the combined river eventually flows out into the Caribbean Sea. It has a...
). The bilineata group is found from north-western 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....
, through the Chocó and Central America
Central America
Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent...
, to southern Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
. The Marañón Gnatcatcher is restricted to the Marañón
Marañón River
The Marañón River rises about 160 km to the northeast of Lima, Peru, flows through a deeply-eroded Andean valley in a northwesterly direction, along the eastern base of the Cordillera of the Andes, as far as 5 degrees 36' southern latitude; then it makes a great bend to the northeast, and...
valley in northern 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....
.
Both the nominate and the bilineata group are found in a wide range of wooded habitats, ranging from the arid woodland and scrub (such as the 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) to humid forest (such as the various types of humid forest in the Amazon). They are mainly found in lowlands below an altitude of 1,000 m (3,300 ft), but the taxon maior, which is restricted to dry woodland and scrub, is found at altitudes of 200-2,700 m (650-8,850 ft).
In dense humid forest, it is typically found at 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...
height, but it is commonly seen a lower levels in more open habitats. The Tropical Gnatcatcher gleans spider
Spider
Spiders are air-breathing arthropods that have eight legs, and chelicerae with fangs that inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other groups of organisms...
s and their eggs, beetle
Beetle
Coleoptera is an order of insects commonly called beetles. The word "coleoptera" is from the Greek , koleos, "sheath"; and , pteron, "wing", thus "sheathed wing". Coleoptera contains more species than any other order, constituting almost 25% of all known life-forms...
s, caterpillar
Caterpillar
Caterpillars are the larval form of members of the order Lepidoptera . They are mostly herbivorous in food habit, although some species are insectivorous. Caterpillars are voracious feeders and many of them are considered to be pests in agriculture...
s and other 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 from outer twigs and foliage. Moving about alone or in pairs, it often joins mixed-species feeding flock
Mixed-species feeding flock
A mixed-species feeding flock, also termed a mixed-species foraging flock, mixed hunting party or informally bird wave, is a flock of usually insectivorous birds of different species, that join each other and move together while foraging...
s with tanager
Tanager
The tanagers comprise the bird family Thraupidae, in the order Passeriformes. The family has an American distribution.There were traditionally about 240 species of tanagers, but the taxonomic treatment of this family's members is currently in a state of flux...
s, New World warbler
New World warbler
The New World warblers or wood-warblers are a group of small, often colorful, passerine birds restricted to the New World. They are not related to the Old World warblers or the Australian warblers....
s and honeycreeper
Honeycreeper
The typical honeycreepers are small birds in the tanager family. They are found in the tropical New World from Mexico south to Brazil.They occur in the forest canopy, and, as the name implies, they are specialist nectar feeders with long curved bills....
s.
The nest is a small cup like that of a hummingbird
Hummingbird
Hummingbirds are birds that comprise the family Trochilidae. They are among the smallest of birds, most species measuring in the 7.5–13 cm range. Indeed, the smallest extant bird species is a hummingbird, the 5-cm Bee Hummingbird. They can hover in mid-air by rapidly flapping their wings...
, constructed from vegetable fibres 6.5 – 28 ft (2–8 m) high on a tree branch. The female lays two or three brown-spotted white eggs in May and June.
This is a curious bird and unafraid of humans; this behavior renders it vulnerable to predators however. Even omnivorous mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s as small as the Common Marmoset
Common Marmoset
The common marmoset is a New World monkey. It originally lived on the Northeastern coast of Brazil, in the states of Piaui, Paraiba, Ceará, Rio Grande do Norte, Pernambuco, Alagoas and Bahia...
(Callithrix jacchus) will eagerly plunder Tropical Gnatcatcher nests in the undergrowth – perhaps more often during the dry season
Dry season
The dry season is a term commonly used when describing the weather in the tropics. The weather in the tropics is dominated by the tropical rain belt, which oscillates from the northern to the southern tropics over the course of the year...
when fruits are scarce – despite the birds' attempts to defend their offspring.
Conservation status
In general, this species is common and widespread throughout most of its range. Consequently, it considered to be of least concernLeast Concern
Least Concern is an IUCN category assigned to extant taxon or lower taxa which have been evaluated but do not qualify for any other category. As such they do not qualify as threatened, Near Threatened, or Conservation Dependent...
by BirdLife International
BirdLife International
BirdLife International is a global Partnership of conservation organisations that strives to conserve birds, their habitats and global biodiversity, working with people towards sustainability in the use of natural resources...
and IUCN. In the Amazon, this species is primarily associated with relatively open habitats (e.g. Várzea Forest), resulting in it being rather local. It may benefit from the opening of the forest caused by deforestation
Deforestation
Deforestation is the removal of a forest or stand of trees where the land is thereafter converted to a nonforest use. Examples of deforestation include conversion of forestland to farms, ranches, or urban use....
, at least as long as some stands of trees remain. The Marañón Gnatcatcher remains common, but is restricted to a small region with extensive habitat destruction
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...
. Three other taxa with highly restricted distributions may be threatened, these being anteocularis of the Magdalena Valley (Colombia), daguae of the Cauca Valley (Colombia), and cinericia of Coiba Island (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...
).
External links
- Tropical Gnatcatcher: Photos, vocalizations from "Avifauna of the Interior of Ceará, Brasil"