Spatial and temporal variation in the provisioning behaviour of female rockhopper penguins Eudyptes chrysocome filholi
Résumé
As seabirds are central place foragers during breeding, their provisioning behaviour and their ability to face variable energy demand from the chicks is expected to vary with environmental conditions. The provisioning behaviour of female rockhopper penguins Eudyptes chrysocome filholi was recorded over the chick-rearing period at Kerguelen (KER) and Crozet (CRO) archipelagoes (two very distinct marine environments), using time-depth recorders, or VHF transmitters coupled with an automatic recording station. No influences of the method have been found on the average foraging trip durations. Some previously undescribed short and multiple trips within a day were recorded using the automatic recording system. These multiple trips (6.8 h) were mostly performed with B/ 5 days old chicks, a period during which feeding rates were the highest (1.1 meals per day), at both sites. During the brooding period, both KER and CRO females mainly performed daily trips of increasing duration (2 h longer at CRO) and at decreasing frequency. During the cre`che compared to the brooding period, females from KER performed slightly fewer daily trips (0.6 per day) and more (B/ 3 days) overnight trips, while females from CRO performed very few daily trips (0.1 per day) and more overnight trips, some of them being long trips lasting 5 to 29 days, mostly initiated during the transition between the brooding and the cre`che periods. The result fit the hypothesis that long trips permit females to restore and/or maintain their body condition at more distant foraging places. It seemed that chick developement during the brooding period and environmental factors during the cre`che period conditioned trip duration of females. Due to more long trips at CRO, the female feeding frequency was twice as high at KER than at CRO during the cre`che period, while males participated in the feeding duties. Based on differences in female behaviour, we hypothesize that the male's contribution is likely to differ strongly from one site to another, and may buffer the possible decrease in female feeding frequency by feeding the chicks if food is less abundant.