Individual quality persists between years: individuals retain body condition from one winter to the next in teal.
Résumé des auteurs (anglais):
Few studies have considered how body condition changes over time in individual birds, and most of these concerned long-lived breeding birds. We used a large database of Common Teal Anas crecca ringed and recaptured while wintering in the Camargue to study inter-annual persistence in wing length and body condition. Winter body condition may be a major determinant of survival during that season, and may further be related to breeding success. Indices of condition were compared for individual Teal between the moments of ringing and of recapture the following winter, analyzing each sex and age class (adult or juvenile) separately. Wing length was highly repeatable between years, though some limited annual variation was also recorded in adult males. Using scaled mass index as an index of body condition, we observed that condition at ringing was the strongest predictor of body condition at recapture for males and juvenile females, although inter- and intra-annual variation was also significant in most cases. The value of the slope for the relationship between individual body condition indices at ringing and recapture did not differ from 1 for males and for adults, whereas, for juvenile females, the slope was significantly greater than 1, indicating that individual differences in condition became more exaggerated over time. When analyses were repeated using crude body mass instead of a condition index, results were generally similar. Birds recaptured the following winter had a greater body condition at ringing that those that were not recaptured, supporting the hypothesis of a link between winter body condition and return probability. Our results demonstrate the importance of a head start in Teal, given persistent effects of obtaining better condition in the first winter, and suggest specific age and sex effects. They also underline the value of condition indices as a long-term predictor of individual quality in birds, even during the non-breeding season and for such a relatively short-lived species.
Auteurs du document :
GUILLEMAIN M., GREEN A. J., SIMON G., GAUTHIER-CLERC M.