Pale crag martin

Appearance

The pale crag martin of the nominate subspecies "P. o. obsoleta" is 12–13 centimetres 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 and the tail averages 4.8 cm. 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.

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.

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.

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.

Naming

There are several subspecies differing in plumage shade or size, although the differences are clinal, and races interbreed where their ranges meet.

Distribution

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.

Habitat

The natural breeding habitat is hilly or mountainous country with cliffs, gorges and caves up to 3,700 m 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.

Reproduction

Pale crag martin pairs often nest alone, especially in the Sahara, although where suitable sites are available small loose colonies may form. This martin aggressively defends its nesting territory against conspecifics and other species. In Africa breeding dates vary geographically and with local weather conditions, but in northwest Africa February to April is normal, and in Asia nesting is from April to June. Two broods are common, and three have been raised in a season.

The nest, built by both adults over several weeks, is made from several hundred mud pellets and lined with feathers and soft, dry grass, hair, sheep's wool or plant down. It may be a half-cup when constructed under an overhang on a vertical wall or cliff, or shaped as a bowl like that of the barn swallow when placed on a sheltered ledge. The nest may be built on a rock cliff face, in a crevice or on a man-made structure, and is re-used for the second brood and in subsequent years. Caves are found in limestone formations and in the lava flows which cover much of western Saudi Arabia, and their ceilings are a favoured location for nesting pale crag martins, red-rumped swallows, and the little swifts which may appropriate the hirundines' nests. In buildings, nests are usually constructed against concrete, which provides adhesion similar to that of rock, but metal walls are sometimes used, and nests may be supported on beams or other horizontal supports. Birds sometimes breed in occupied buildings, and there is a record of a pair nesting in a busy restaurant kitchen. Artificial nests are readily used, and halved coconut shells have been successfully occupied in Abu Dhabi.

The clutch is usually two or three buff-white eggs blotched with sepia or grey-brown, particularly at the wide end. The average egg size for Asian birds was 19.3 mm × 12.9 mm with a weight of 1.7 g. Both adults incubate the eggs for 16–19 days prior to hatching and feed the chicks about ten times an hour until they fledge and for several days after they can fly. The fledging time can vary from 22–24 days to 25–30 days, though the latter estimates probably take into account fledged young returning to the nest for food. If a nest is destroyed, or the breeding attempt otherwise fails, a replacement clutch may be laid, typically with fewer eggs. Two nests in Arabia were used in spring and again in the autumn, but it is not known if the same pair were involved.

Food

The pale crag martin feeds mainly on insects caught in flight, but will occasionally feed on the ground. Breeding birds often feed close to their nesting territory, flying back and forth along a rock face catching insects in their bills. Cliff faces generate standing waves in the airflow which concentrate insects near vertical areas. Crag martins exploit the area close to the cliff when they hunt, relying on their high manoeuvrability. When not breeding, they may also hunt low over open ground. The insects caught depend on what is locally available, but may include mosquitoes, flies, Hymenoptera, ants and beetles. This martin often feeds alone, but sizeable groups may gather at grass fires to feast on the fleeing insects, and outside the breeding season flocks of up to 300 may form where food is abundant, such as agricultural areas, wetlands and sewage works. The pale crag martin drinks in flight as it skims the water surface; some of its water requirement is obtained from the insects it consumes. Wintering hirundines of other species are not normally found in the dry, rocky areas in which the pale crag martin nests, so there is little competition for food.

Predators

Some falcons have the speed and agility to catch swallows and martins in flight, and pale crag martins may be hunted by species such as the peregrine falcon, Taita falcon, African hobby and wintering Eurasian hobby. Pale crag martins often share their nesting sites with little swifts, which sometimes forcibly take over martins' nests.

The argasid tick "Hyalomma marginatum" was found in pale crag martin nests on a sarcophagus and an ancient tomb in Egypt. This tick has been implicated in the transmission of Bahig virus, a pathogenic arbovirus previously thought to be transmitted only by mosquitoes. Another argasid tick, "Argas africolumbae", was found in a nest of the closely related rock martins in Kenya. The nasal mite "Ptilonyssus echinatus" was found in a pale crag martin in the Tibesti Mountains of northern Chad.