Effect of natural brood size variability on growth and survival of thornbird nestlings

SARAVIA-PIETROPAOLO, MJ; MANZOLI, DE; ANTONIAZZI, LR; QUIROGA, MA; BELDOMENICO PM

JOURNAL OF ZOOLOGY

Wiley

Año: 2016 vol. 300 p. 59 - 66

0022-5460

For many bird species, brood size is a highly variable trait. Several aspects of thedevelopment and survival of nestlings are affected by brood size. Most scienticevidence comes from brood manipulation experiments, and the complementaryinformation offered by studies of natural variability has received little attention intropical and subtropical species. Here, we provide data on the effect of brood sizeon the development and survival of two furnariid species under natural conditions.Weekly during two breeding seasons, two forest patches (40 ha. each) from centralArgentina, were exhaustively examined for active nests. Nestlings were monitoredrepeatedly from hatching to edging. Factors that were considered potential confoundersor effect modiers were also recorded and included in the statistical analysis.We found a positive effect of brood size on growth, and a negative effect onsurvival. The rst effect was only observed when preceding weeks were not rainy,and the latter was present in only one breeding season, so both effects appeared todepend on environmental conditions. Our results suggest that the benet of a largeor small brood size is dependent on context. In the studied populations, plasticityin or within-population genetic diversity in brood size may be advantageous in thelight of the unpredictable circumstances that will prevail during the breedingseason.