Swallow (bird)
| Swallow | |
|---|---|
 |
|
| Red-rumped swallow | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Passeriformes |
| Suborder: | Passeri |
| Family: |
Hirundinidae Rafinesque, 1815 |
| Genera | |
|
19, see text. |
|
19, see text.
The swallows and martins are a group of passerine birds in the family Hirundinidae that are characterised by their adaptation to aerial feeding. Swallow is used colloquially in Europe as a synonym for the barn swallow.
This family comprises two subfamilies: Pseudochelidoninae (the river martins of the genus Pseudochelidon) and Hirundininae (all other swallows and martins). Within the Old World, the name "martin" tends to be used for the squarer-tailed species, and the name "swallow" for the more fork-tailed species; however, there is no scientific distinction between these two groups. Within the New World, "martin" is reserved for members of the genus Progne. (These two systems are responsible for the sand martin being called "bank swallow" in the New World.) The entire family contains around 83 species in 19 genera.
The swallows have a cosmopolitan distribution across the world and breed on all the continents except Antarctica. It is believed that this family originated in Africa as hole-nesters; Africa still has the greatest diversity of the species. They also occur on a number of oceanic islands. A number of European and North American species are long-distance migrants; by contrast, the West and South African swallows are non-migratory.
The swallows and martins have an evolutionarily conservative body shape which is similar across the clade but is unlike that of other passerines. Swallows have adapted to hunting insects on the wing by developing a slender, streamlined body and long pointed wings, which allow great maneuverability and endurance, as well as frequent periods of gliding. Their body shape allows for very efficient flight; the metabolic rate of swallows in flight is 49–72% lower than equivalent passerines of the same size.
Like the unrelated swifts and nightjars, which hunt in a similar way, they have short bills, but strong jaws and a wide gape. Their body length ranges from about 10–24 cm (3.9–9.4 in) and their weight from about 10–60 g (0.35–2.12 oz). The wings are long, pointed, and have nine primary feathers. The tail has 12 feathers and may be deeply forked, somewhat indented, or square-ended. A long tail increases maneuverability, and may also function as a sexual adornment, since the tail is frequently longer in males. In barn swallows the tail of the male is 18% longer than those of the female, and females will select mates on the basis of tail length.
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