1. Small interannual variability in the body mass of a seabird with high flight costs.
- Author
-
Okado, Jumpei and Watanuki, Yutaka
- Subjects
- *
CHICKS , *SEA birds , *COST , *ENERGY industries , *RHINOCEROSES - Abstract
Seabird parents during chick rearing is hypothesized to regulate body mass to reduce flight costs and invest energy in current reproduction. Alcids have 2‒4 times higher wing-loading and higher flight costs than other seabirds. In particular, rhinoceros auklets Cerorhincamonocerata (RHAU) carry the heaviest meals among alcids despite its medium-size, therefore, we expected that they might be more likely to keep their body mass small and within a narrow range during chick rearing. We examined between-breeding stage and interannual variations in RHAU body mass using 27-year monitoring data, then tested whether the interannual variation shown by the coefficient of variation (CV) in body mass during chick rearing was smaller than in other seabirds, and if their body lipid stores were smaller. RHAU during chick rearing have 15‒20 g lower body mass, corresponding to 5‒7% decrease of flight costs, than those during incubation. We found that CV of body mass in RHAU (1.4) was smaller than those of 10 other seabird species (1.7‒7.5), while CVs in provisioning metrics, such as meal mass, chick growth, fledgling mass, and fledging success, were the largest or second largest. RHAU body lipid stores during chick rearing (3.8‒4.0%) was also smaller than six other species (5.7‒9.5%). Results suggest that chick-rearing RHAU maintained a narrow range of body mass with minimum body lipid stores, possibly because of their greater wing-loading and heavier meals. Such constraints on body mass regulation might affect their variable investment in their chicks under environmental variability, as shown large variation in provisioning metrics. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF