Group size modulates time budget and foraging efficiency in captive Skylarks, Alauda arvensis
Résumé
Skylarks (Alauda arvensis) are known to adopt a typical aggregative behaviour during the wintering period. A further benefit is that individuals in larger groups can decrease the amount of time they spent being vigilant, while maintaining a high probability of predator detection. Using wild birds temporarily housed in outdoor aviaries, we investigated the influence of group size (1, 2 and 4 individuals) on individual time budget (vigilance vs. foraging), and the pecking (number of pecks) and intake rates (number of seeds consumed). Results showed that individuals reduced their vigilance and increased their pecking rate when group size increased. However, the intake rate was not maximised in the largest group suggesting that large flocks would negatively affect individual foraging efficiency. A consideration of the whole set of costs and benefits will be necessary before the adaptive value of group living in any species can be fully assessed.