Foraging tactics in dynamic sea‐ice habitats affect individual state in a long‐ranging seabird
Résumé
1. Individual heterogeneity in diet and foraging behaviour is common in wild animalpopulations, and can be a strong determinant of how populations respond toenvironmental changes. Within populations, variation in foraging behaviour andthe occurrence of individual tactics in relation to resources distribution can helpexplain differences in individual fitness, and ultimately identify important factorsaffecting population dynamics. We examined how foraging behaviour and habitatduring the breeding period related to the physiological state of a long-rangingseabird adapted to sea ice, the Antarctic petrel Thalassoica antarctica.2. Firstly, using GPS tracking and state-switching movement modelling (hidden Markovmodels) on 124 individual birds, we tested for the occurrence of distinct foraging tacticswithin our study population. Our results highlight a large variation in the movementand foraging behaviour of a very mobile seabird, and delineate distinct foragingtactics along a gradient from foraging in dense pack ice to foraging in open water.3. Secondly, we investigated the effects of these foraging tactics on individual stateat return from a foraging trip. We combined movement data with morphometricand physiological measurements of a suite of plasma metabolites that provideda general picture of a bird's individual state. Foraging in denser sea ice was associatedwith lower gain in body mass during brooding, as well as lower level ofenergy acquisition (plasma triacylglycerol) during both brooding and incubation.We found no clear relationship between the foraging tactic in relation to sea iceand the energetic stress (changes in plasma corticosterone), energetic balance(β-hydroxybutyrate) or trophic level (δ15N). However, a shorter foraging range wasrelated to both the energetic balance (positively) and the trophic level (negatively).4. Our results highlight a diverse range of foraging tactics in relation to sea ice inAntarctic petrels. While the various foraging tactics do not seem to stronglyalter energetic balance, they may affect other aspects of Antarctic petrels'physiology. Future changes in sea-ice habitats can thus be expected to have animpact on the individual state of seabirds such as Antarctic petrels, which couldultimately affect their population dynamics. Nonetheless, strong individual heterogeneityin the use of sea-ice habitats by a typical pagophilic species mightstrengthen its resilience to environmental changes and in particular to forecastedsea-ice loss.
| Origine | Fichiers éditeurs autorisés sur une archive ouverte |
|---|---|
| Licence |