Time of breeding and female condition affect chick growth in the Chilean Swallow (Tachycineta meyeni).

LILJESTHROM, M.; SCHIAVINI, A.; REBOREDA, J.C.

EMU

CSIRO PUBLISHING

Año: 2012 vol. 112 p. 157 - 161

0158-4197

We analyzed growth of nestling Chilean Swallows (Tachycineta meyeni) over four consecutive breeding seasons and determined factors that explain variation in growth rate, asymptotic body mass and length of the nestling period. As the breeding season advanced nestlings grew slower and attained lower asymptotic mass, but length of the nestling period and nestling survival did not show any seasonal trend. Nestling asymptotic body mass increased with female body condition, which was negatively correlated with time of breeding, suggesting that seasonal decline in asymptotic body mass could be the result of changes in environmental conditions or lower quality of females breeding later in the season. There was no relationship between average minimum ambient temperature and either growth rate or asymptotic mass during the nestlings first 10 days of age. However, short periods of poor weather and snowfall had an important effect on nestling survival. Growth rate (0.43) was lower than that of other Tachycineta species nesting at similar latitudes in the northern hemisphere but similar to those of subtropical species of the genus, suggesting that factors that have influenced the evolution of this life history trait differ between Chilean and other Swallow species. Nestling growth of this population of Chilean swallows seems to fit better with a southern hemisphere life history than with a high latitude one.