Mascarene martin

The Mascarene martin or Mascarene swallow (Phedina borbonica) is a passerine bird in the swallow family that breeds in Madagascar and in the Mascarene Islands. The nominate subspecies occurs on Mauritius and Réunion and has never been found away from the Mascarene Islands, but the smaller Madagascan subspecies, P. b. madagascariensis, is migratory and has been recorded wintering in East Africa or wandering to other Indian Ocean islands.

The Mascarene martin is a small swallow that has grey-brown underparts becoming white on the throat and lower abdomen, dark grey-brown upperparts and a slightly forked tail. The underparts are heavily streaked with black. It nests in small colonies anywhere with suitably sheltered sites for constructing a nest, such as ledges, buildings, tunnels, caves or amongst rocks. The nest is a shallow cup of twigs and other plant material, and the normal clutch is two or three brown-spotted white eggs. The incubation and fledging times are unknown. The Mascarene martin has a heavy flight with slow wingbeats interspersed with glides, and frequently perches on wires. It feeds on insects in flight, often hunting low over the ground or vegetation. In eastern Africa, open habitats such as deforested areas are frequently used for hunting. A number of internal and external parasites have been detected in this species.

Tropical cyclones can adversely affect populations on the smaller islands, but the Mascarene martin is a locally common bird with an apparently stable population and is classed as a species of Least Concern by the International Union for Conservation of Nature (IUCN). Its legal protection ranges from none on the French overseas department of Réunion to a status on Mauritius as a "species of wildlife in respect of which more severe penalties are provided".

Adult Mascarene martins of the nominate subspecies are 15 cm (5.9 in) long with wings averaging 117 mm (4.6 in) and weigh 23.9 g (0.84 oz). This small hirundine has dark brown-grey upperparts with faint streaking. It has grey-brown underparts becoming white on the throat and lower abdomen, all being heavily streaked with black. The slightly forked tail averages 54.6 mm (2.15 in) long and has white edges to the brown undertail coverts. The wings are blackish-brown and the bill and legs are black. The eyes are dark brown and the black bill averages 11.3 mm (0.44 in) long. The sexes are similar, but juvenile birds have more diffuse breast streaking, and white tips to the feathers covering the closed wing. The Madagascan subspecies is overall paler and larger-billed than the nominate form. It has denser streaking on the breast, but only very fine lines on the lower abdomen and on the white undertail. It is distinctly smaller than the nominate subspecies, 12–14 cm (4.7–5.5 in) in length with an average weight of 20.6 g (0.73 oz). This martin moults in December and January on Mauritius, and Madagascan breeders wintering on the African mainland moult in June and July.

The Mascarene martin is a relatively quiet bird, but it has a warbled siri-liri siri-liri song given in flight or when perched; some calls given by perched birds end in a glissando. Other vocalisations may be used during mating or displays of aggression. There is a chip contact call, and the young birds produce a fast twittering sound when begging for food. Birds wintering in mainland Africa are usually silent.

No other streaked swallow species occur within the island breeding range of the Mascarene martin, and in Africa the lesser striped swallow is larger, has a deeply forked tail and a very different plumage, with dark blue upperparts, a red rump and a chestnut head. The brown-throated sand martin has similar structure and plumage colour to the Mascarene martin, but has plain, unstreaked underparts. The small Mascarene swiftlet has longer, narrower wings than the martin, and a much lighter flight. The Brazza's martin is smaller, has a plainer back and finer dashing on the throat and chest, but there is no range overlap.