Hirundinidae Swallows
Version: 1.0 — Published March 4, 2020
Introduction
Like the swifts, treeswifts, and woodswallows that they superficially resemble, swallows are highly specialized aerial insectivores. Feeding on aerial plankton that is constantly varying with the vagaries of the weather, their lifestyle is in many ways more like that of a storm-petrel than a typical passerine. They cannot defend a territory around foraging grounds, and they split up their habitats by places where they nest and what kind of nest they build more than by what they eat. With nest-site often comes social system, and this varies from solitary to highly colonial. Intensely territorial in the immediate vicinity of their nests, most migratory species aggregate in enormous nocturnal roosts once the breeding season is past.
Habitat
Swallows live in almost all open habitat types, with only a few living in densely forested areas, and most species often found near water.
Diet and Foraging
Hirundinids are almost exclusively insectivorous, primarily feeding on insects on the wing. However, some species, most notably the Tree Swallow Tachycineta bicolor, feed on berries during migration and winter when flying insects are more scarce.
Breeding
Swallows are generally monogamous with biparental care, albeit with high levels of extra-pair fertilizations documented in some species and low levels of simultaneous polygyny in some. Swallow nests are of three general types: burrows in sandy soils, adopted cavities, and nests made of mud. Within the last, shapes vary from open cups, through closed cups, to retort globe-shaped with long access tunnels. Females lay 2 to 8 eggs, with most clutches in the range of 3 to 6 and larger clutches away from the tropics. Nest-building and incubation are by both sexes or by the female alone, and the nestlings are provisioned by both attending adults. Incubation takes 10 to 21 days, with most species in the range of 14 to 18 days, and the nestlings leave the nest at three to four weeks post-hatch. Post-fledging parental care varies from none to feeding for up to ten days post-fledge.
Conservation Status
Habitat destruction is the primary threat facing hirundinids, seven species of which (9%) are of conservation concern (4 VU, 2 EN, 1 CR). The critically endangered White-eyed River Martin Pseudochelidon sirintarae, known only from its wintering grounds in Thailand, has not been reliably seen since the 1980’s and may well be extinct. Its decline may be linked to habitat loss and hunting of the large flocks that used to gather at winter roost sites, but this is hard to judge without knowledge of its breeding grounds and threats that might have been at play there. A number of other swallow species are range-restricted and of concern, including Bahama and Golden Swallows (Tachycineta cyaneoviridis and T. euchrysea, respectively) in the Caribbean and Blue and White-tailed Swallows in Africa (Hirundo atrocaerulea and H. megaensis, respectively). Aerial insectivores in North America and Europe appear to be suffering range-wide declines, so far very poorly understood, but climate change and increased effectiveness of agricultural insect control appear to be likely contributing factors.
Systematics History
Hirundinidae is part of the sylvioid radiation, but its relative position within this large superfamily remains uncertain. Hirundinidae is perhaps sister to a clade that includes Scotocercidae, Aegithalidae, and Phylloscopidae (Alström et al. 2006, Barker et al. 2004), or in a polytomy of three clades: Hirundinidae, Pycnonotidae, and the above group plus the babbler radiation including Timaliidae, Sylviidae, and others (Alström et al. 2011a). Most recent studies, however, have found Hirundinidae involved in polytomies that include various groupings of most of the rest of Sylvioidea (Johansson et al. 2008b, Gelang et al. 2009, Irestedt et al. 2011, Fregin et al. 2012, Alström et al. 2013a, Olsson et al. 2013). We have made a tentative list of related families above, but clearly, much further work will be required to identify the sister taxa to Hirundinidae with greater certainty. Within Hirundinidae, there are two distinct subfamilies, with the two species in Pseudochelidoninae sister to the rest of the species in Hirundininae (Sheldon et al. 2005) and three clades in the latter distinguishable largely by nesting habits: mud-nesters, burrowers, and cavity adopters (Winkler & Sheldon 1993).
Conservation Status
Least Concern |
80.7%
|
---|---|
Near Threatened |
1.1%
|
Vulnerable |
4.5%
|
Endangered |
2.3%
|
Critically Endangered |
1.1%
|
Extinct in the Wild |
0%
|
Extinct |
0%
|
Not Evaluated |
0%
|
Data Deficient |
2.3%
|
Unknown |
8%
|
Data provided by IUCN (2023) Red List. More information
Related families
In addition to Pnoepygidae, Hirundinidae appears close to a large radiation of the Sylvioidea, including Timaliidae, Pycnonotidae, and Phylloscopidae.