The breeding biology of White-rumped Swallows, Tachycineta leucorrhoa: a comparison with other congeners

MASSONI, V.; BULIT, F.; REBOREDA, J.C.

Veracruz, México

Congreso; 4th. North American Ornithological Conference; 2006

Ornithological Societies of North America

 V. Massoni, F. Bulit, J.C. Reboreda. The White-rumped Swallow, Tachycineta leucorrhoa, is a poorly known Southern Hemisphere species, and meaningful insights can be drawn by comparing its breeding biology with the tropical and temperate members of the genus. During the 2002 to 2005 breeding seasons we monitored 17, 24, 62, and 90 nesting attempts respectively, at Chascomús, Buenos Aires, Argentina. Males were significantly bigger (head + bill) and lighter than females (n = 15 and 145). Clutch size of first clutches averaged 4.9 eggs, and the egg mass to female mass ratio was 0.09. Egg survival, hatching success, and fledging success were 83%, 85% and 87%, respectively, and the incubation and nestling period lasted 15 and 24 days. The eggs took 1 to 4 days to hatch but most nests (62 %) showed synchronous hatching; brood reduction affected 10% of the nests (18/175), causing the death of 1.5 nestlings. During 2004 and 2005, we realized that 5% and 16 % of nesting attempts were true second broods and, except for a reduction in clutch size to 4.33 eggs, no other differences between first and second broods were found. Therefore, the White-rumped Swallow breeding biology appears to be intermediate between that of North Temperate and Tropical congeners.