Variables affecting egg and yolk mass of White-rumped Swallows (Tachycineta leucorrhoa)

MELINA BARRIONUEVO; FLORENCIA BULIT; VIVIANA MASSONI

Campos de Jordao

Congreso; XXV International Ornithological Congress; 2010

AQUAVIVA

Egg size can have important consequences in nestling´s survival via nestling´s hatching weight and growth rate. Although females may vary their investment in egg size according to body condition or the environment, it is the yolk size the variable that might have the greatest importance for the embryos` growth and development. With a nondestructive technique we estimated yolk mass via candling and digital photographs of White-rumped Swallow eggs at Chascomús, Buenos Aires Province, Argentina during the 2007 breeding season. We evaluated the effects of date of egg laying, environmental conditions, laying order, female condition and food abundance on egg and yolk mass. We also seek to establish if egg mass can predict yolk mass accurately. Both egg and yolk mass increased with laying order (p