Diet and foraging behaviour of the British Storm Petrel Hydrobates pelagicus in the Bay of Biscay during summer.

The diet and the foraging behaviour of the British Storm Petrel Hydrobates pelagicus during the breeding period were studied from proventriculus contents obtained from adults belonging to two populations in the Bay of Biscay. The observed prey had various ecological affinities in two main groups. The first group were oceanic and neritic organisms, such as ichthyoplankton (Gadidae, Ammodytidae, Myctophidae) and microzooplankton (Copepoda, Euphausiacea, Chaetognatha, Anthomedusae, and meroplanktonic larvae), including bioluminescent species migrating vertically at night from deep water to the surface. The second group were littoral (Gobiidae) and suprabenthic intertidal organisms (mainly isopods Cirolanidae). 52% of total prey was zooplankton, and a further large percentage (37%) were littoral and intertidal benthic organisms. Our results show that British Storm Petrels regularly forage inshore during summer nights. This behaviour is not only linked to the necessity for breeders to feed their chick, but seems to be part of the foraging strategy of this species, enabling individuals to optimize their time-energy budgets. A relationship between the importance of inshore food resources and both colony location and colony size is suggested

D Elbee J. & Hemery G., ARDEA 86 (1): 1-10.