Fueling Incubation: Differential use of Body Stores in Arcticand Temperate-Breeding Barnacle Geese (Branta leucopsis)

• Published in: The Auk
• Main Authors: Götz Eichhorn, Henk P. Van Der Jeugd, Harro A. J. Meijer, Rudolf H. Drent
• Format: Text
• Language: English
• Published: American Ornithological Society 2010
• Subjects: Arctic; Barents Sea; Branta leucopsis
• Online Access: https://doi.org/10.1525/auk.2009.09057

We compared the use of body stores in breeding Barnacle Geese (Branta leucopsis) in traditional Arctic colonies in the Barents Sea with that in recently established temperate-zone breeding colonies in the Baltic Sea and North Sea by studying female body-mass loss and use of fat and protein stores during incubation. Average daily body-mass loss was almost identical in the 2 temperatebreeding populations (17.0 g and 16.5 g in Baltic Sea and North Sea, respectively), whereas Arctic-breeding females lost significantly less (10.6 g day-1). Temperate-breeding females initiated incubation with body mass 125 g higher than that of Arctic breeders, but at the end of incubation, body mass was similar among the 3 populations, averaging 1,458 g. Body-mass loss during incubation amounted to 23% (North Sea), 22% (Baltic Sea), and 15% (Barents Sea). Fat mass, as measured by isotope dilution in a subsample of females, was consistently higher in North Sea than in Barents Sea birds, but both populations showed similar rates of fat-mass loss (9.4 g day-1, on average). By contrast, loss of fat-free mass (assumed to represent wet protein) amounted to 9.3 g day-1 in North Sea birds but only 1.5 g day-1 in Barents Sea birds. Energy content of 1 g utilized body mass was 21.1 kJ (North Sea) and 34.9 kJ (Barents Sea), which equates to 376 kJ day-1 and 415 kJ day-1 drawn from stored energy, respectively. We suggest that differences in nest-attendance and postincubation demands are responsible for the differential use of body stores in temperate- and Arctic-breeding Barnacle Geese.