Pale Crag-Martin

Identificazione

The pale crag martin of the nominate subspecies P. o. obsoleta is 12–13 centimetres (4+1⁄2–5 inches) long with light brown upperparts, becoming paler on the lower back, and a short square tail that has small white patches near the tips of all but the central and outermost pairs of feathers. It has a pale grey throat, upper breast and underwing coverts, and the rest of the underparts are a dirty white. The eyes are brown, the small bill is mainly black, and the legs are brownish-pink. The wing length averages 13 cm (5 in) and the tail averages 4.8 cm (1+7⁄8 in). The sexes are similar in appearance, but juveniles have pale edges to the upperparts and flight feathers. The other subspecies differ from the nominate form as detailed in the table above.<p>This martin moults early, with adults having completely replaced their feathers by late August. Juveniles moult somewhat later, and their old primary feathers are retained even when the body has mainly adult plumage.<p>The pale crag martin's flight is slow, with rapid wing beats interspersed with flat-winged glides, and it is more acrobatic than the larger Eurasian crag martin. It is a quiet bird; the song is a muffled twitter, and other calls include a trrt resembling the call of the common house martin, a nasal vick, and a high-pitched twee contact call.<p>The pale crag martin is much drabber than most African swallows, and confusion is unlikely except with other crag martins or with sand martins of the genus Riparia. It is 15% smaller, paler and greyer than the Eurasian crag martin, and has smaller tail spots. It is smaller, paler, and has a more contrasting throat than the rock martin. In the far east of its range, the pale crag martin always has lighter underparts than the dusky crag martin. Although only slightly larger than the sand martin and brown-throated sand martin, the pale crag martin is more robust, has white tail spots, and lacks a breast band. Separation of similar species in flight may be complicated by the difficulty of judging colours accurately in strong desert light, particularly with juveniles. The fast flight of the brown-throated sand martin also makes identification more difficult.

Tassonomia

The pale crag martin was first formally described in 1851 by German ornithologist Jean Cabanis as Cotyle obsoleta, using a specimen collected from near Cairo, Egypt. It was moved to the new genus Ptyonoprogne, created by German ornithologist Heinrich Gustav Reichenbach, in the same year. The genus name is derived from the Ancient Greek ptuon (πτύον), "a fan", referring to the shape of the opened tail, and Procne (Πρόκνη), a mythological girl who was turned into a swallow. The specific name obsoleta means "worn" in Latin.<p>The Ptyonoprogne 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 martins. DNA sequence studies suggest that there are three major groupings within the Hirundininae, broadly correlating with the type of nest built. These 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 Ptyonoprogne species construct open mud nests and therefore belong to the last group. Hirundo species also build open nests, Delichon house martins have a closed nest, and the Cecropis and Petrochelidon swallows have retort-like closed nests with an entrance tunnel.<p>The genus Ptyonoprogne is closely related to the larger swallow genus Hirundo, and is sometimes included within it since the nests of the Ptyonoprogne crag martins resemble those of typical Hirundo species like the barn swallow. However, a DNA analysis showed that if Hirundo is enlarged to contain the crag martins, it should include all the mud-builder genera. Conversely, if the Delichon house martins are considered to be a separate genus, as is normally the case, Cecropis, Petrochelidon and Ptyonoprogne should also be split off. The pale crag martin's nearest relatives are the other members of the genus, the dusky crag martin P. concolor of southern Asia, the rock martin P. fuligula of Southern Africa, and the Eurasian crag martin P. rupestris.<p>The pale crag martin was formerly often treated as the small, pale northern subspecies of the rock martin, but it is now usually considered to be a separate species. The changes in size and colour are continuous, so the evidence for separate species is not strong, although some rock martins can weigh more than twice as much as the smallest subspecies of the pale crag martin. The average weight for P. f. fusciventris is 22.4 grams (346 grains) against 10 g (150 gr) for P. o. obsoleta. There do not appear to be any intermediate forms where pale crag martins and rock martin populations breed close to each other in Somalia and Ethiopia.<p>In areas of Pakistan where its range overlaps with that of the dusky crag martin, the pale crag martin breeds at a higher altitude. Its range does not overlap there with the Eurasian crag martin, which is found high in the Himalayas, but where both occur in Iran, the pale crag martin favours more arid habitats. In North Africa, the Eurasian species is again found at a higher level. The separation by altitude and aridity means that it is not known whether the closely related Ptyonoprogne martins could hybridise. If they were shown to do so, it would cast doubts on their specific distinctness.<p>There are several subspecies differing in plumage shade or size, although the differences are clinal, and races interbreed where their ranges meet.

Nome scientifico

Ptyonoprogne obsoleta

Autorità

(Cabanis, 1851)

Ordine

Passeriformi

Famiglia

Hirundinidae

Genere

Ptyonoprogne

Areale e habitat

The pale crag martin breeds in suitable habitats throughout northern Africa and through the Middle East as far as Afghanistan and Pakistan. It is largely resident apart from local movements or a descent to lower altitudes after breeding. In addition, there is some short-range movement, including martins from southern Arabia crossing the Red Sea and wintering alongside the local breeding birds in Ethiopia and the Horn of Africa, and non-breeding P. f. spatzi and P. f. presaharica joining rock martins in Mali and Mauritania. In Pakistan, the breeding range of the subspecies P. f. peloplasta overlaps with that of the dusky crag martin, although that species breeds at much lower levels, and in North Africa P. f. obsoleta occupies desert habitats whilst the Eurasian crag martin is found in the mountains. The pale crag martin has been recorded as a vagrant in Bahrain, Qatar, Kuwait, and Sri Lanka, although its occurrence in the last country is treated as unproven in a 2011 field guide. The martin has been claimed to visit Turkey, but this is also disputed.<p>The natural breeding habitat is hilly or mountainous country with cliffs, gorges and caves up to 3,700 m (12,100 ft) above sea level, but this martin also breeds in lowlands, especially if rocks or buildings are available, and may be found far from water. This species readily uses man-made structures as a substitute for natural precipices, and has bred on houses in southern Israel since the 1970s. In Egypt it may breed near monuments like Abu Simbel or in desert towns such as Aswan. It uses towns, bridges and cliffs in Ethiopia, and tower blocks in Arabia. In the breeding season, the martin needs mud or wet soil to construct its nests, and this is normally readily found near human habitations. This species appears to be scarce in some forested and coastal areas with high humidity, in which the red-rumped swallow tends to be the common hirundine.

Migrazione

Migratori completi

Comportamento

Comportamento migratorio: Migratori completi.

Conservazione

Tendenza della popolazione: in aumento.

Tendenza della popolazione

in aumento