page_title: Eurasian crag martin
section_title: Breeding
hierarchical_section_title: Eurasian crag martin / Behaviour / Breeding
caption_attribution_description: Español: Nido de avión roquero con tres crías. Poncebos, Asturias. English: Three well-grown chicks in a nest in Asturias
context_page_description: The Eurasian crag martin or just crag martin is a small passerine bird in the swallow family. It is about 14 cm long with ash-brown upperparts and paler underparts, and a short, square tail that has distinctive white patches on most of its feathers. It breeds in the mountains of southern Europe, northwestern Africa and across the Palearctic. It can be confused with the three other species in its genus, but is larger than both, with brighter tail spots and different plumage tone. Many European birds are resident, but some northern populations and most Asian breeders are migratory, wintering in northern Africa, the Middle East or India.
  The Eurasian crag martin builds a nest adherent to the rock under a cliff overhang or increasingly onto a man-made structure. It makes a neat half-cup mud nest with an inner soft lining of feathers and dry grass. Nests are often solitary, although a few pairs may breed relatively close together at good locations. Two to five brown-blotched white eggs are incubated mainly by the female, and both parents feed the chicks. This species does not form large breeding colonies, but is gregarious outside the breeding season.
context_section_description: Crag martin pairs nest alone or in small colonies, usually containing fewer than ten nests. Nests are on average 30 m (98 ft) apart and each pair aggressively defends its breeding territory against other crag martin and most other bird species. Nesting takes place from May to August, and usually two broods are raised. The nest, built by both adults, is an open half cup made of mud and lined with soft material such as feathers or dry grass. It is constructed under an overhang on a rock cliff face, in a crevice or cave, or on a man-made structure. It takes one to three weeks to build and is re-used for the second brood and in subsequent years. The clutch is two to five eggs with an average of three. The eggs are white with brownish blotches particularly at the wide end, and average 20.2 mm × 14.0 mm (0.80 in × 0.55 in) with a weight of 2.08 g (0.073 oz). The eggs are incubated mainly by the female for 13–17 days to hatching, and the chicks take another 24–27 days to fledge. Both parents feed the chicks bringing food every two to five minutes, and the young are fed for 14–21 days after fledging. With such frequent feeding rates the adults mainly forage in the best hunting zones in the immediate vicinity of the nest, since the further they fly to forage the longer it would take to bring food to the chicks in the nest. In an Italian study, the hatching rate was 80.2 percent, and the average number of fledged young was 3.1.
  The crag martin has over the last few decades increasingly used houses and other man-made sites to nest. This greater availability of breeding sites has enabled the species to expand its range, but it is possible that this will lead to competition with other hirundines, such as the barn swallow and common house martin, which also use artificial nest sites.
  An Italian study showed that, as with other aerial feeders, the start of breeding was delayed by cold or wet weather, but this had no influence on the clutch size nor on the number of fledged young. Unexpectedly, it was found that once the eggs had hatched there was a negative relationship between temperature and the number of fledged young. The authors suggested that hot weather dried up the small rivers where the parents found food. Colony size did not influence the laying date, the clutch size or the number of successfully fledged young, but this species does not form large colonies anyway.
caption: Nest with young
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