Editing Swallow (section)

===Breeding===
[[File:Nesting Swallows at Skomer Island, Wales.webm|thumb|Swallow chicks nesting at the [[Skomer|Skomer Marine Conservation Zone]], 2017: Video by [[Natural Resources Wales]]]]
[[File:Cliff Swallow-27527-2.jpg|thumb|left|Two [[American cliff swallow]]s constructing mud nests]]
The more primitive species nest in existing cavities, for example in an old [[woodpecker]] nest, while other species excavate burrows in soft substrate such as sand banks.<ref name ="HBW"/> Swallows in the genera ''Hirundo'', ''Ptyonoprogne'', ''Cecropis'', ''Petrochelidon'', ''Atronanus'' and ''Delichon'' build mud nests close to overhead shelter in locations that are protected from both the weather and predators. The mud-nesters are most common in the Old World, particularly Africa, whereas cavity-nesters are more common in the New World. Mud-nesting species in particular are limited in areas of high humidity, which causes the mud nests to crumble. Many cave-, bank-, and cliff-dwelling species of swallows nest in large colonies. Mud nests are constructed by both males and females, and amongst the tunnel diggers, the excavation duties are shared, as well. In historical times, the introduction of man-made stone structures such as barns and bridges, together with forest clearance, has led to an abundance of colony sites around the globe, significantly increasing the breeding ranges of some species. Birds living in large colonies typically have to contend with both [[parasitism|ectoparasite]]s and conspecific [[brood parasite|nest parasitism]].<ref>{{cite journal | last1 = Brown | first1 = C | last2 = Brown | first2 = M | year = 1986 | title = Ectoparasitism as a Cost of Coloniality in Cliff Swallows (''Hirundo pyrrhonota'') | journal = Ecology | volume = 67 | issue = 5| jstor=1938676| pages = 1206–1218 | doi = 10.2307/1938676 | bibcode = 1986Ecol...67.1206B | url = http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1475&context=natrespapers | url-access = subscription }}</ref><ref>{{cite journal | last1 = Brown | first1 = C | year = 1984 | title = Laying Eggs in a Neighbor's Nest: Benefit and Cost of Colonial Nesting in Swallows | journal = Science | volume = 224 | issue = 4648| pages = 518–519 | doi = 10.1126/science.224.4648.518 | pmid = 17753777 | bibcode = 1984Sci...224..518B | s2cid = 21128259 }}</ref> In barn swallows, old mated males and young unmated males benefit from colonial behaviour, whereas females and mated young males likely benefit more from nesting by themselves.<ref name="Møller1987">{{cite journal|last1=Møller|first1=Anders Pape|title=Advantages and disadvantages of coloniality in the swallow, ''Hirundo rustica''|journal=Animal Behaviour|volume=35|issue=3|year=1987|pages=819–832|issn=0003-3472|doi=10.1016/S0003-3472(87)80118-5|s2cid=53185342}}</ref>

Pairs of mated swallows are monogamous,<ref>[http://www.eeb.cornell.edu/winkler/botw/hirundinidae.html Hirundinidae] {{Webarchive|url=https://web.archive.org/web/20020504182255/http://www.eeb.cornell.edu/winkler/botw/hirundinidae.html |date=2002-05-04 }}. eeb.cornell.edu</ref> and pairs of nonmigratory species often stay near their breeding area all year, though the nest site is defended most vigorously during the breeding season. Migratory species often return to the same breeding area each year, and may select the same nest site if they were previously successful in that location. First-year breeders generally select a nesting site close to where they were raised.<ref>[http://www.answers.com/topic/swallows-hirundinidae-biological-family Swallows (Hirundinidae)] {{Webarchive|url=https://web.archive.org/web/20090129193740/http://www.answers.com/topic/swallows-hirundinidae-biological-family |date=2009-01-29 }}. Answers.com</ref> The breeding of temperate species is seasonal, whereas that of subtropical or tropical species can either be continuous throughout the year or seasonal. Seasonal species in the subtropics or tropics usually time their breeding to coincide with the peaks in insect activity, which is usually the wet season, but some species, such as the [[white-bibbed swallow]], nest in the dry season to avoid flooding in their riverbank nesting habitat.<ref name ="HBW"/> All swallows defend their nests from egg predators, although solitary species are more aggressive towards predators than colonial species.<ref name = "colonial">{{cite journal | last1 = Snapp | first1 = B | year = 1976 | title = Colonial Breeding in the Barn Swallow (Hirundo rustica) and Its Adaptive Significance | url = http://sora.unm.edu/sites/default/files/journals/condor/v078n04/p0471-p0480.pdf | journal = The Condor | volume = 78 | issue = 4| pages = 471–480 | doi = 10.2307/1367096 | jstor = 1367096 }}</ref> Overall, the contribution of male swallows towards parental care is the highest of any passerine bird.<ref name ="HBW"/>

{{multiple image
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 | image1 = Wire tailed swallow2 @kannur.jpg
 | alt1 = Parent approaching with food
 | image2 = Wire tailed swallow @kannur.jpg
 | alt2 = Transferring the food
 | footer = A [[wire-tailed swallow]] feeding a recently fledged chick
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The [[egg (biology)|eggs]] of swallows tend to be white, although those of some mud-nesters are speckled. The typical [[avian clutch size|clutch size]] is around four to five eggs in temperate areas and two to three eggs in the tropics. The [[avian incubation|incubation]] duties are shared in some species, and in others the eggs are incubated solely by the females. Amongst the species where the males help with incubation, their contribution varies amongst species, with some species such as the cliff swallow sharing the duties equally and the female doing most of the work in others. Amongst the barn swallows, the male of the American subspecies helps (to a small extent), whereas the European subspecies does not. Even in species where the male does not incubate the eggs, he may sit on them when the female is away to reduce heat loss (this is different from incubation as that involves warming the eggs, not just stopping heat loss). Incubation stints last for 5–15 minutes and are followed by bursts of feeding activity. From laying, swallow eggs take 10–21 days to hatch, with 14–18 days being more typical.<ref name ="HBW"/>

The chicks of swallows hatch naked, generally with only a few tufts of down. The eyes are closed and do not fully open for up to 10 days. The feathers take a few days to begin to sprout, and the chicks are brooded by the parents until they are able to [[thermoregulate]]. On the whole, they develop slowly compared to other passerine birds. The parents do not usually feed the chicks individual insects, but instead feed a bolus of food comprising 10–100 insects. Regardless of whether the species has males that incubate or brood the chicks, the males of all hirundines help feed the chicks. When the young [[fledge]] is difficult to determine, as they are enticed out of the nest after three weeks by parents, but frequently return to the nest afterwards to roost.<ref name ="HBW"/>