Delichon
Encyclopedia
Delichon is a small genus
of passerine
bird
s that belongs to the swallow
family and contains three species
named as house martins. These are chunky, bull-headed and short-tailed birds, blackish-blue above with a contrasting white rump, and with white or grey underparts. They have feathering on the toes and tarsi
that is characteristic of this genus. The house martins are closely related to other swallows that build mud nests
, particularly the Hirundo
barn swallows. They breed only in Europe
, Asia and the mountains of North Africa
. Two species, the Common and Asian House Martin
s, migrate
south in winter, while the Nepal House Martin
is resident in the Himalayas
year-round.
The house martins nest in colonies on cliffs or buildings, constructing feather- or grass-lined mud nests. The typical clutch
is two or three white eggs
; both parents build the nest, incubate
the eggs and feed the chicks. These martins are aerial hunters of small insects such as flies
and aphid
s. Despite their flying skills the Delichon martins are sometimes caught by fast-flying birds of prey
. They may carry flea
s or internal parasite
s. None of the species are considered threatened
, although widespread reductions in Common House Martin numbers have been reported from central and northern Europe. This decline is due to factors including poor weather, poisoning by agricultural pesticide
s, lack of mud for nest building and competition with House Sparrow
s for nest sites.
s. DNA
studies suggest that there are three major groupings within the Hirundininae, broadly correlating with the type of nest built. The groups are the "core martins" including burrowing species like the Sand Martin
, the "nest-adopters", which are birds like the Tree Swallow
that utilise natural cavities, and the "mud nest builders". The Delichon species construct a closed mud nest and therefore belong to the latter group; they appear to be intermediate between the Hirundo
and Ptyonoprogne
species that make open cup nests, and the Cecropis
and Petrochelidon
swallows, which have retort-like
closed nests with an entrance tunnel. The genetic evidence suggests a close relationship between Hirundo
and Delichon, which is further supported by the frequency of interbreeding between two widespread species, the Barn Swallow
and the Common House Martin, despite being their being in different genera. The suggested taxonomic sequence of the mud-building swallows has been recommended by at least two European taxonomic committees.
The genus Delichon was created by American naturalist Thomas Horsfield
and British entomologist
Frederic Moore
in 1854 to accommodate the Nepal House Martin that was first described by Moore in the same year, and is therefore the type species
for the genus. The two other house martins were moved to Delichon from the genus Chelidon in which they had been placed up to that time. The name of the new genus, "Delichon", is an anagram
of the Ancient Greek
term χελιδον/chelidôn, meaning swallow.
The genus contains three similar species:
The Common and Asian House Martins have sometimes been considered to be a single species, although both breed in the western Himalayas
without hybridising. There is also limited DNA evidence that suggests a significant genetic distance
between these two martins.
genus with all three species breeding only in the northern hemisphere. The Common House Martin is a widespread migrant breeder across Europe, north Africa and all northern temperate Asia to Kamchatka
. Its western subspecies D. u. urbicum winters in tropical Africa, and eastern D. u. lagopodum moves to southern China
and Southeast Asia
. The Asian House Martin breeds further south than Common House Martin in the mountains of central and eastern Asia; its nominate subspecies winters in Southeast Asia
, but the races breeding in the Himalayan and Taiwan may just move from the high mountains to lower altitudes. The Nepal House Martin is resident in the mountains of southern Asia.
The preferred habitat of the Common House Martin is open country with low vegetation, such as pasture, meadows and farmland, and preferably near water, although it is also found in mountains up to at least 2,200 metres (7,200 ft) altitude. As its name implies, it readily nests on man-made buildings, and will breed even in city centres if the air is clean enough. The other two species favour mountainous country (and sea cliffs in the case of Asian House Martin); they use buildings as nest sites less frequently than their northern relative. The wintering grounds of the two migrant species include a range of open country and hilly habitats.
. The Common House Martin is the largest bird of the three, with an average weight of 18.3 g (0.65 oz), and has the most deeply forked tail; the Nepalese species is the smallest (15 g, 0.53 oz) and has the squarest tail. Distinctive species plumage
features are the black chin and black undertail coverts
of Nepal House Martin, and the greyish wash to the underparts of Asian House Martin. As with other swallows and martins, the moult is slow and protracted because of the need to maintain efficient flight at all times to enable feeding. Moult normally starts on arrival at the wintering grounds, but overlaps with the breeding season for the non-migratory Nepal House Martin.
The Delichon martins have simple flight calls of one to three notes. In the two more widespread species these have a distinctive buzzing quality. The male's song is a short simple ripple, perhaps less musical than that given by other swallows.
As a group, the house martins cannot easily be confused with any other swallows. Four species of the genus Tachycineta
have white rumps and underparts, but they have bright metallic green or blue-green upperparts, longer tails, and are restricted to Central and South America. The variable plumages of the South Asian species and a confused taxonomic history has left their distribution ranges in doubt.
David Winkler and Frederick Sheldon believe that evolutionary development in the mud-building swallows, and individual species follow this order of construction. A retort builder like Red-rumped Swallow
starts with an open cup, closes it, and then builds the entrance tunnel. Winkler and Sheldon propose that the development of closed nests reduced competition between males for copulations with the females. Since mating occurs inside the nest, the difficulty of access means other males are excluded. This reduction in competition permits the dense breeding colonies typical of the Delichon martins.
The urban Common House Martin has to compete with House Sparrows, which frequently attempt to take over the nest during construction, with the House Martins rebuilding elsewhere if the sparrows are successful. The entrance at the top of the completed cup is so small that the sparrows cannot take over the nest once it is finished.
As with other swallows, pairing and copulation displays are normally brief, taking just a few minutes. The male calls to a female and attempts to lead her to the nest, where he lands and continues calling while posing with lowered head, dropped wings and ruffled throat. If he is successful, the female calls and allows him to mount her, usually in the nest. Three or four white eggs are the normal clutch
and all three species are frequently double-brooded
. Both sexes build the nest, incubate the eggs and feed the chicks, although the female does most of the incubation, which normally lasts 14–16 days. The newly hatched chicks are altricial
, and after a further 22–32 days, depending on weather, the chicks leave the nest. The fledge
d young stay with, and are fed by, the parents for about a week after leaving the nest. Occasionally, young birds from the first brood will assist in feeding the second brood.
A Scottish study showed that mortality in Common House Martins occurred mostly outside the breeding season and averaged 57%. Females that had raised two clutches in a season had a higher mortality than those that were single-brooded, but there was no such correlation for the males.
, aphids
and Hymenoptera
such as winged ants. A wide range of other insects are caught, including Lepidoptera
, beetle
s and lacewing
s. The Asian House Martin appears to occasionally take terrestrial springtail
s and larva
e and the Common House Martin also sometimes feeds on the ground. These martins are gregarious, feeding in flocks often with other aerial predators like swift
s, or other hirundines
such as the Barn
or Striated Swallow
s. In the case of at least the Common House Martin, the start of egg laying appears to be linked to the appearance of large numbers of flying aphids, which provide a stable and abundant food supply.
(Falco subbuteo
). Birds of the Delichon species are most vulnerable when collecting mud from the ground. This has therefore become a communal activity, with a group of these birds descending suddenly on a patch of mud. The generally insectivorous Collared Falconet
has been recorded as hunting Nepal House Martin.
The house martins are parasitised by flea
s and mite
s, including the "House Martin Flea", Ceratophyllus hirundinis and its relatives. A Polish study of the Common House Martin showed that nests typically contained more than 29 species of ectoparasite, with C. hirundinis and another swallow specialist, Oeciacus hirundinis, the most abundant. The genus also hosts endoparasites
such as Haemoproteus prognei (avian malaria
), which are transmitted by blood-sucking insects including mosquitoes.
More than 40 beetle species have been recorded in Common House Martin nests, but most are either typical of the locality or found in the nests of other birds. The typical number of individuals, around 200, is relatively low compared to other bird species (1,400 individual beetles for House Sparrow, 2,000 for Sand Martin
). The beetles have no effect on the nesting birds, and the reason for their comparatively low numbers is unknown, although the numbers of specific parasites found in House Martin's nests is also quite small.
of species. A species is assessed as subject to varying levels of threat if it has a small, fragmented or declining range, or if the total population is less than 10,000 mature individuals, or if numbers have dropped rapidly (by more than 10% in ten years or three generations). None of the three Delichon species meets these criteria, and three genus house martins are therefore considered of Least Concern
.
The numbers of the two Asian species are unknown, but both can be locally common or abundant, and the Asian House Martin is extending its range in southern Siberia
. The lowland breeding Common House Martin has greatly benefited from forest clearance, creating the open habitats it prefers, and from human habitation which has given it an abundance of safe man-made nest sites, although widespread declines in its numbers have been reported from central and northern Europe since 1970. This is due to factors including poor weather, poisoning by agricultural pesticides, lack of mud for nest building and competition with House Sparrows for nest sites. Despite this, the huge geographical range and large numbers of the Common House Martin mean that its global status is secure.
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 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 that belongs to the swallow
Swallow
The swallows and martins are a group of passerine birds in the family Hirundinidae which are characterised by their adaptation to aerial feeding...
family and contains three species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
named as house martins. These are chunky, bull-headed and short-tailed birds, blackish-blue above with a contrasting white rump, and with white or grey underparts. They have feathering on the toes and tarsi
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...
that is characteristic of this genus. The house martins are closely related to other swallows that build mud 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...
, particularly the Hirundo
Hirundo
The bird genus Hirundo is a group of passerines in the family Hirundinidae . These are the typical swallows, including the widespread Barn Swallow. Many of this group have blue backs, red on the face and sometimes the rump or nape, and whitish or rufous underparts...
barn swallows. They breed only in Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, Asia and the mountains of North Africa
North Africa
North Africa or Northern Africa is the northernmost region of the African continent, linked by the Sahara to Sub-Saharan Africa. Geopolitically, the United Nations definition of Northern Africa includes eight countries or territories; Algeria, Egypt, Libya, Morocco, South Sudan, Sudan, Tunisia, and...
. Two species, the Common and Asian House Martin
Asian House Martin
The Asian House Martin is a migratory passerine bird of the swallow family Hirundinidae. It has mainly blue-black upperparts, other than its white rump, and has pale grey underparts. Its three subspecies breed in the Himalayas and in central and eastern Asia, and spend the winter lower in the...
s, migrate
Bird migration
Bird migration is the regular seasonal journey undertaken by many species of birds. Bird movements include those made in response to changes in food availability, habitat or weather. Sometimes, journeys are not termed "true migration" because they are irregular or in only one direction...
south in winter, while the Nepal House Martin
Nepal House Martin
The Nepal House Martin is a non-migratory passerine of the swallow family Hirundinidae. Its two subspecies breed in the Himalayas from northwestern India through Nepal to Burma, northern Vietnam, and just into China...
is resident in the Himalayas
Himalayas
The Himalaya Range or Himalaya Mountains Sanskrit: Devanagari: हिमालय, literally "abode of snow"), usually called the Himalayas or Himalaya for short, is a mountain range in Asia, separating the Indian subcontinent from the Tibetan Plateau...
year-round.
The house martins nest in colonies on cliffs or buildings, constructing feather- or grass-lined mud nests. The typical clutch
Clutch (eggs)
A clutch of eggs refers to all the eggs produced by birds or reptiles, often at a single time, particularly those laid in a nest.In birds, destruction of a clutch by predators, , results in double-clutching...
is two or three white eggs
Bird egg
Bird eggs are laid by females and incubated for a time that varies according to the species; a single young hatches from each egg. Average clutch sizes range from one to about 17...
; both parents build the nest, incubate
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...
the eggs and feed the chicks. These martins are aerial hunters of small insects such as flies
Fly
True flies are insects of the order Diptera . They possess a pair of wings on the mesothorax and a pair of halteres, derived from the hind wings, on the metathorax...
and aphid
Aphid
Aphids, also known as plant lice and in Britain and the Commonwealth as greenflies, blackflies or whiteflies, are small sap sucking insects, and members of the superfamily Aphidoidea. Aphids are among the most destructive insect pests on cultivated plants in temperate regions...
s. Despite their flying skills the Delichon martins are sometimes caught by fast-flying 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....
. They may carry flea
Flea
Flea is the common name for insects of the order Siphonaptera which are wingless insects with mouthparts adapted for piercing skin and sucking blood...
s or internal 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. None of the species are considered threatened
Threatened species
Threatened species are any speciesg animals, plants, fungi, etc.) which are vulnerable to endangerment in the near future.The World Conservation Union is the foremost authority on threatened species, and treats threatened species not as a single category, but as a group of three categories,...
, although widespread reductions in Common House Martin numbers have been reported from central and northern Europe. This decline is due to factors including poor weather, poisoning by agricultural pesticide
Pesticide
Pesticides are substances or mixture of substances intended for preventing, destroying, repelling or mitigating any pest.A pesticide may be a chemical unicycle, biological agent , antimicrobial, disinfectant or device used against any pest...
s, lack of mud for nest building and competition with House Sparrow
House Sparrow
The House Sparrow is a bird of the sparrow family Passeridae, found in most parts of the world. One of about 25 species in the genus Passer, the House Sparrow occurs naturally in most of Europe, the Mediterranean region, and much of Asia...
s for nest sites.
Taxonomy
The three Delichon species are members of the swallow family of birds, and are classed as members of the Hirundininae subfamily which comprises all swallows and martins except the very distinctive river martinRiver martin
The river martins form a distinctive subfamily Pseudochelidoninae within the swallow and martin bird family Hirundinidae. The two species are the African River Martin Pseudochelidon eurystomina, found in the Congo and Gabon, and the White-eyed River Martin Pseudochelidon sirintarae, known only from...
s. DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
studies suggest that there are three major groupings within the Hirundininae, broadly correlating with the type of nest built. The groups are the "core martins" including burrowing species like the Sand Martin
Sand Martin
The Sand Martin is a migratory passerine bird in the swallow family. It has a wide range in summer, embracing practically the whole of Europe and the Mediterranean countries, part of northern Asia and also North America. It winters in eastern and southern Africa, South America and South Asia...
, the "nest-adopters", which are birds like the Tree Swallow
Tree Swallow
The Tree Swallow, Tachycineta bicolor, is a migratory passerine bird that breeds in North America and winters in Mexico, Central America and the Caribbean. It is a very rare vagrant to western Europe....
that utilise natural cavities, and the "mud nest builders". The Delichon species construct a closed mud nest and therefore belong to the latter group; they appear to be intermediate between the Hirundo
Hirundo
The bird genus Hirundo is a group of passerines in the family Hirundinidae . These are the typical swallows, including the widespread Barn Swallow. Many of this group have blue backs, red on the face and sometimes the rump or nape, and whitish or rufous underparts...
and Ptyonoprogne
Ptyonoprogne
The crag martins are three species of small passerine birds in the genus Ptyonoprogne of the swallow family. They are the Eurasian Crag Martin , the Rock Martin and the Dusky Crag Martin . They are closely related to each other, and have formerly sometimes been considered to be one species...
species that make open cup nests, and the Cecropis
Cecropis
Cecropis is a genus of large swallows found in Africa and tropical Asia. The Red-rumped Swallow's range also extends into southern Europe. This genus is frequently subsumed into the larger genus Hirundo.The species are:...
and Petrochelidon
Petrochelidon
Petrochelidon is a genus of birds known as cliff-nesting swallows.It contains the following species:-Species in taxonomic order:* Red-throated Cliff Swallow * Preuss's Cliff Swallow...
swallows, which have retort-like
Retort
In a chemistry laboratory, a retort is a glassware device used for distillation or dry distillation of substances. It consists of a spherical vessel with a long downward-pointing neck. The liquid to be distilled is placed in the vessel and heated...
closed nests with an entrance tunnel. The genetic evidence suggests a close relationship between Hirundo
Hirundo
The bird genus Hirundo is a group of passerines in the family Hirundinidae . These are the typical swallows, including the widespread Barn Swallow. Many of this group have blue backs, red on the face and sometimes the rump or nape, and whitish or rufous underparts...
and Delichon, which is further supported by the frequency of interbreeding between two widespread species, the Barn Swallow
Barn Swallow
The Barn Swallow is the most widespread species of swallow in the world. It is a distinctive passerine bird with blue upperparts, a long, deeply forked tail and curved, pointed wings. It is found in Europe, Asia, Africa and the Americas...
and the Common House Martin, despite being their being in different genera. The suggested taxonomic sequence of the mud-building swallows has been recommended by at least two European taxonomic committees.
The genus Delichon was created by American naturalist Thomas Horsfield
Thomas Horsfield
Thomas Horsfield M. D. was an American physician and naturalist.Horsfield was born in Bethlehem, Pennsylvania, and studied medicine at the University of Pennsylvania. He was the grandson of Timothy Horsfield, Sr., a colonel and justice of the peace in Bethlehem, and a friend mentioned in Benjamin...
and British entomologist
Entomology
Entomology is the scientific study of insects, a branch of arthropodology...
Frederic Moore
Frederic Moore
Frederic Moore FZS was a British entomologist. It has been said that Moore was born at 33 Bruton Street but may be incorrect given that this was the address of the menagerie and office of the Zoological Society of London from 1826 to 1836.Moore was appointed an assistant in the East India Company...
in 1854 to accommodate the Nepal House Martin that was first described by Moore in the same year, and is therefore the type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
for the genus. The two other house martins were moved to Delichon from the genus Chelidon in which they had been placed up to that time. The name of the new genus, "Delichon", is an anagram
Anagram
An anagram is a type of word play, the result of rearranging the letters of a word or phrase to produce a new word or phrase, using all the original letters exactly once; e.g., orchestra = carthorse, A decimal point = I'm a dot in place, Tom Marvolo Riddle = I am Lord Voldemort. Someone who...
of the Ancient Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
term χελιδον/chelidôn, meaning swallow.
The genus contains three similar species:
- Common House Martin (Delichon urbicum) originally described as Hirundo urbica by Linnaeus in 1758.
- Asian House MartinAsian House MartinThe Asian House Martin is a migratory passerine bird of the swallow family Hirundinidae. It has mainly blue-black upperparts, other than its white rump, and has pale grey underparts. Its three subspecies breed in the Himalayas and in central and eastern Asia, and spend the winter lower in the...
(Delichon dasypus) described as Chelidon dasypus by BonaparteCharles Lucien BonaparteCharles Lucien Jules Laurent Bonaparte, 2nd Prince of Canino and Musignano was a French naturalist and ornithologist.-Biography:...
in 1850. - Nepal House MartinNepal House MartinThe Nepal House Martin is a non-migratory passerine of the swallow family Hirundinidae. Its two subspecies breed in the Himalayas from northwestern India through Nepal to Burma, northern Vietnam, and just into China...
(Delichon nipalense) described by Moore in 1854.
The Common and Asian House Martins have sometimes been considered to be a single species, although both breed in the western Himalayas
Himalayas
The Himalaya Range or Himalaya Mountains Sanskrit: Devanagari: हिमालय, literally "abode of snow"), usually called the Himalayas or Himalaya for short, is a mountain range in Asia, separating the Indian subcontinent from the Tibetan Plateau...
without hybridising. There is also limited DNA evidence that suggests a significant genetic distance
Genetic distance
Genetic distance refers to the genetic divergence between species or between populations within a species. It is measured by a variety of parameters. Smaller genetic distances indicate a close genetic relationship whereas large genetic distances indicate a more distant genetic relationship...
between these two martins.
Distribution and habitat
Delichon is an Old WorldOld World
The Old World consists of those parts of the world known to classical antiquity and the European Middle Ages. It is used in the context of, and contrast with, the "New World" ....
genus with all three species breeding only in the northern hemisphere. The Common House Martin is a widespread migrant breeder across Europe, north Africa and all northern temperate Asia to Kamchatka
Kamchatka Peninsula
The Kamchatka Peninsula is a peninsula in the Russian Far East, with an area of . It lies between the Pacific Ocean to the east and the Sea of Okhotsk to the west...
. Its western subspecies D. u. urbicum winters in tropical Africa, and eastern D. u. lagopodum moves to southern China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
and Southeast Asia
Southeast Asia
Southeast Asia, South-East Asia, South East Asia or Southeastern Asia is a subregion of Asia, consisting of the countries that are geographically south of China, east of India, west of New Guinea and north of Australia. The region lies on the intersection of geological plates, with heavy seismic...
. The Asian House Martin breeds further south than Common House Martin in the mountains of central and eastern Asia; its nominate subspecies winters in Southeast Asia
Southeast Asia
Southeast Asia, South-East Asia, South East Asia or Southeastern Asia is a subregion of Asia, consisting of the countries that are geographically south of China, east of India, west of New Guinea and north of Australia. The region lies on the intersection of geological plates, with heavy seismic...
, but the races breeding in the Himalayan and Taiwan may just move from the high mountains to lower altitudes. The Nepal House Martin is resident in the mountains of southern Asia.
The preferred habitat of the Common House Martin is open country with low vegetation, such as pasture, meadows and farmland, and preferably near water, although it is also found in mountains up to at least 2,200 metres (7,200 ft) altitude. As its name implies, it readily nests on man-made buildings, and will breed even in city centres if the air is clean enough. The other two species favour mountainous country (and sea cliffs in the case of Asian House Martin); they use buildings as nest sites less frequently than their northern relative. The wintering grounds of the two migrant species include a range of open country and hilly habitats.
Description
Delichon martins are 13–15 cm (5–6 in) long, blackish blue above with a contrasting white rump, and with white or grey underparts. They are chunky, bull-headed and short-tailed birds, and have feathering on the toes and tarsiTarsus (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...
. The Common House Martin is the largest bird of the three, with an average weight of 18.3 g (0.65 oz), and has the most deeply forked tail; the Nepalese species is the smallest (15 g, 0.53 oz) and has the squarest tail. Distinctive species 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...
features are the black chin and black undertail coverts
Covert (feather)
A covert feather on a bird is one of a set of feathers, called coverts, which as the name implies, cover other feathers. The coverts help to smooth airflow over the wings and tail.- Wing-coverts :...
of Nepal House Martin, and the greyish wash to the underparts of Asian House Martin. As with other swallows and martins, the moult is slow and protracted because of the need to maintain efficient flight at all times to enable feeding. Moult normally starts on arrival at the wintering grounds, but overlaps with the breeding season for the non-migratory Nepal House Martin.
The Delichon martins have simple flight calls of one to three notes. In the two more widespread species these have a distinctive buzzing quality. The male's song is a short simple ripple, perhaps less musical than that given by other swallows.
As a group, the house martins cannot easily be confused with any other swallows. Four species of the genus Tachycineta
Tachycineta
Tachycineta is a genus of birds in the swallow family. There are nine described species. Its members are restricted to the Americas....
have white rumps and underparts, but they have bright metallic green or blue-green upperparts, longer tails, and are restricted to Central and South America. The variable plumages of the South Asian species and a confused taxonomic history has left their distribution ranges in doubt.
Breeding
The Delichon martins were originally cliff nesters, breeding in colonies situated under an overhang on a vertical cliff. However, the House Martin now largely uses human structures, as, to a lesser extent, does the Asian House Martin. The typical nest is a grass or feather-lined deep closed mud bowl with a small opening at the top, but many Asian House Martins leave the top of the nest open.David Winkler and Frederick Sheldon believe that evolutionary development in the mud-building swallows, and individual species follow this order of construction. A retort builder like Red-rumped Swallow
Red-rumped Swallow
The Red-rumped Swallow is a small passerine bird in the swallow family. It breeds in open hilly country of temperate southern Europe and Asia from Portugal and Spain to Japan, India and tropical Africa. The Indian and African birds are resident, but European and other Asian birds are migratory...
starts with an open cup, closes it, and then builds the entrance tunnel. Winkler and Sheldon propose that the development of closed nests reduced competition between males for copulations with the females. Since mating occurs inside the nest, the difficulty of access means other males are excluded. This reduction in competition permits the dense breeding colonies typical of the Delichon martins.
The urban Common House Martin has to compete with House Sparrows, which frequently attempt to take over the nest during construction, with the House Martins rebuilding elsewhere if the sparrows are successful. The entrance at the top of the completed cup is so small that the sparrows cannot take over the nest once it is finished.
As with other swallows, pairing and copulation displays are normally brief, taking just a few minutes. The male calls to a female and attempts to lead her to the nest, where he lands and continues calling while posing with lowered head, dropped wings and ruffled throat. If he is successful, the female calls and allows him to mount her, usually in the nest. Three or four white eggs are the normal clutch
Clutch
A clutch is a mechanical device which provides for the transmission of power from one component to another...
and all three species are frequently double-brooded
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...
. Both sexes build the nest, incubate the eggs and feed the chicks, although the female does most of the incubation, which normally lasts 14–16 days. The newly hatched chicks are 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...
, and after a further 22–32 days, depending on weather, the chicks leave the nest. The fledge
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...
d young stay with, and are fed by, the parents for about a week after leaving the nest. Occasionally, young birds from the first brood will assist in feeding the second brood.
A Scottish study showed that mortality in Common House Martins occurred mostly outside the breeding season and averaged 57%. Females that had raised two clutches in a season had a higher mortality than those that were single-brooded, but there was no such correlation for the males.
Feeding
The Delichon species typically feed higher in the air, and take smaller prey than other swallows. It is believed that this reduces inter-specific food competition, particularly with the Barn Swallow which shares much of the breeding and wintering range of the martins. The insects eaten are mostly small fliesFly
True flies are insects of the order Diptera . They possess a pair of wings on the mesothorax and a pair of halteres, derived from the hind wings, on the metathorax...
, aphids
Aphis
Aphis may refer to:* Aphis, a genus of aphid species* Animal and Plant Health Inspection Service , organizational unit of the USDA* HMS Aphis , Royal Navy insect class gunboat...
and Hymenoptera
Hymenoptera
Hymenoptera is one of the largest orders of insects, comprising the sawflies, wasps, bees and ants. There are over 130,000 recognized species, with many more remaining to be described. The name refers to the heavy wings of the insects, and is derived from the Ancient Greek ὑμήν : membrane and...
such as winged ants. A wide range of other insects are caught, including Lepidoptera
Lepidoptera
Lepidoptera is a large order of insects that includes moths and butterflies . It is one of the most widespread and widely recognizable insect orders in the world, encompassing moths and the three superfamilies of butterflies, skipper butterflies, and moth-butterflies...
, 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 and lacewing
Neuroptera
The insect order Neuroptera, or net-winged insects, includes the lacewings, mantidflies, antlions, and their relatives. The order contains some 6,010 species...
s. The Asian House Martin appears to occasionally take terrestrial springtail
Springtail
Springtails form the largest of the three lineages of modern hexapods that are no longer considered insects...
s and larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
e and the Common House Martin also sometimes feeds on the ground. These martins are gregarious, feeding in flocks often with other aerial predators like swift
Swift
The swifts are a family, Apodidae, of highly aerial birds. They are superficially similar to swallows, but are actually not closely related to passerine species at all; swifts are in the separate order Apodiformes, which they share with hummingbirds...
s, or other hirundines
Swallow
The swallows and martins are a group of passerine birds in the family Hirundinidae which are characterised by their adaptation to aerial feeding...
such as the Barn
Barn Swallow
The Barn Swallow is the most widespread species of swallow in the world. It is a distinctive passerine bird with blue upperparts, a long, deeply forked tail and curved, pointed wings. It is found in Europe, Asia, Africa and the Americas...
or Striated Swallow
Striated Swallow
The Striated Swallow is a species of swallow found in open, often hilly areas, clearings and cultivation in South and Southeast Asia from northeastern India and Taiwan south to Timor...
s. In the case of at least the Common House Martin, the start of egg laying appears to be linked to the appearance of large numbers of flying aphids, which provide a stable and abundant food supply.
Predators and parasites
The main predators of the house martins are those birds of prey which are capable of catching these agile fliers, such as the HobbyEurasian Hobby
The Eurasian Hobby , or just simply Hobby, is a small slim falcon. It belongs to a rather close-knit group of similar falcons often considered a subgenus Hypotriorchis.-Description:...
(Falco subbuteo
Eurasian Hobby
The Eurasian Hobby , or just simply Hobby, is a small slim falcon. It belongs to a rather close-knit group of similar falcons often considered a subgenus Hypotriorchis.-Description:...
). Birds of the Delichon species are most vulnerable when collecting mud from the ground. This has therefore become a communal activity, with a group of these birds descending suddenly on a patch of mud. The generally insectivorous Collared Falconet
Collared Falconet
The Collared Falconet is a species of bird of prey in the Falconidae family.It is found in the Indian Subcontinent and Southeast Asia, ranging across Bangladesh, Bhutan, Cambodia, India, Laos, Myanmar, Nepal, Thailand, and Vietnam.Its natural habitat is temperate forests.-References:* BirdLife...
has been recorded as hunting Nepal House Martin.
The house martins are parasitised by flea
Flea
Flea is the common name for insects of the order Siphonaptera which are wingless insects with mouthparts adapted for piercing skin and sucking blood...
s and mite
Mite
Mites, along with ticks, are small arthropods belonging to the subclass Acari and the class Arachnida. The scientific discipline devoted to the study of ticks and mites is called acarology.-Diversity and systematics:...
s, including the "House Martin Flea", Ceratophyllus hirundinis and its relatives. A Polish study of the Common House Martin showed that nests typically contained more than 29 species of ectoparasite, with C. hirundinis and another swallow specialist, Oeciacus hirundinis, the most abundant. The genus also hosts endoparasites
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...
such as Haemoproteus prognei (avian malaria
Avian malaria
Avian malaria is a parasitic disease of birds.-Etiology:Avian malaria is most notably caused by Plasmodium relictum, a protist that infects birds in tropical regions...
), which are transmitted by blood-sucking insects including mosquitoes.
More than 40 beetle species have been recorded in Common House Martin nests, but most are either typical of the locality or found in the nests of other birds. The typical number of individuals, around 200, is relatively low compared to other bird species (1,400 individual beetles for House Sparrow, 2,000 for Sand Martin
Sand Martin
The Sand Martin is a migratory passerine bird in the swallow family. It has a wide range in summer, embracing practically the whole of Europe and the Mediterranean countries, part of northern Asia and also North America. It winters in eastern and southern Africa, South America and South Asia...
). The beetles have no effect on the nesting birds, and the reason for their comparatively low numbers is unknown, although the numbers of specific parasites found in House Martin's nests is also quite small.
Conservation status
The International Union for Conservation of Nature (IUCN) is the organisation responsible for assessing the conservation statusConservation status
The conservation status of a group of organisms indicates whether the group is still extant and how likely the group is to become extinct in the near future...
of species. A species is assessed as subject to varying levels of threat if it has a small, fragmented or declining range, or if the total population is less than 10,000 mature individuals, or if numbers have dropped rapidly (by more than 10% in ten years or three generations). None of the three Delichon species meets these criteria, and three genus house martins are therefore considered of Least Concern
Least 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...
.
The numbers of the two Asian species are unknown, but both can be locally common or abundant, and the Asian House Martin is extending its range in southern Siberia
Siberia
Siberia is an extensive region constituting almost all of Northern Asia. Comprising the central and eastern portion of the Russian Federation, it was part of the Soviet Union from its beginning, as its predecessor states, the Tsardom of Russia and the Russian Empire, conquered it during the 16th...
. The lowland breeding Common House Martin has greatly benefited from forest clearance, creating the open habitats it prefers, and from human habitation which has given it an abundance of safe man-made nest sites, although widespread declines in its numbers have been reported from central and northern Europe since 1970. This is due to factors including poor weather, poisoning by agricultural pesticides, lack of mud for nest building and competition with House Sparrows for nest sites. Despite this, the huge geographical range and large numbers of the Common House Martin mean that its global status is secure.