diagnostics
20-25 cm, 14 g. Adult male Blue Swallow is wholly glossy steel-blue. Birds with worn plumage show more violet than steel-blue. The outer tail feathers are narrow and considerably elongated, with no white spots in the tail. Variable white patches on the sides and flanks conspicuous on resting birds, but otherwise concealed. The adult female Blue Swallow is slightly duller and slightly smaller than the male, with shorter outer tail-feathers. Immature Blue Swallows are rusty black to sooty black in appearance, less glossy blue-black than the adults, with white mottling visible on the flanks. Young birds have outer tail feathers without the filamentous tip to tail streamers similar to that of females, with the streamers always much shorter than in males. (Mackworth-Praed and Grant 1955, Spottiswoode 2005).
trophic
In South Africa and Swaziland, Blue Swallows have been recorded from 760 masl, in the southern part of their range, to a maximum of 1 760 masl in the northern parts of their range (Allan et al. 1987, Monadjem et al. 2003). Blue Swallow nest sites are located within high-altitude, high-rainfall (greater than 1 000 mm per year), undulating, open, primary mist-belt grasslands with a sward height of <0.5 m (Allan et al. 1987, Monadjem et al. 2003, Evans 2010, Evans and Bouwman 2010a). The generation lengths for female and male Blue Swallows are approximately 2.6 and 3 years, respectively (SW Evans unpubl. data). Mean age at first reproduction for female and male Blue Swallows is one and two years of age, respectively (Evans et al. 2002). For both males and females, mortality from ages 0-1 and 1 onwards was estimated to be approximately 50% and 10%, respectively (SW Evans unpubl. data). Maximum age of reproduction for males and females is approximately 4 years (SW Evans unpubl. data). In Mpumalanga, Blue Swallows significantly prefer wetlands to grasslands for foraging (Evans 2010, Evans and Bouwman 2010a) although in KwaZulu-Natal, Wakelin (2006) found that Blue Swallows preferred to forage in the ecotone between grasslands and wetlands. The minimum home range size is approximately 3.3 km2, consisting, at a minimum, of grasslands (2.4 km2 or 73%) and wetlands, including drainage lines (0.9 km2 or 27%) (Evans and Bouwman 2010a). An area of grassland with no drainage lines or other wetlands is considered unlikely to support any Blue Swallow pairs, probably owing to a lack of food (Evans and Bouwman 2010a).
