Clutch Investment in the Chilean Swallow (Tachycineta meyeni) Shifts with Time of Breeding and Position in the Sequence of Laying

[摘要] Abstract. Within a population, the sizes of eggs and clutches vary, and the combination of both determines a female's reproductive investment. We investigated females' investment in clutches of the Chilean Swallow (Tachycineta meyeni) at the southern limit of its range, where it breeds in an extreme climate. We analyzed variation in clutch, egg and yolk size in relation to the female's condition, date of laying, and position in the sequence of laying. As predicted by energy/nutrient constraints, clutch size and yolk size decreased over the breeding season, though egg mass increased. Females' investment strategy differed with clutch size: their investment in eggs increased with each successive egg in clutches of 4 and 5 eggs but decreased with each successive egg in clutches of 3 eggs. Eggs that were heavier for their size were more likely to hatch than eggs light for their size. Females may make a strategic decision, with high investment in eggs laid early resulting in a short sequence (small clutch) and ...

[学科分类] 动物科学

[关键词] egg size;laying order;clutch size;reproductive investment;Tachycineta meyeni