Ardea
Official journal of the Netherlands Ornithologists' Union

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de Korte J. & Wattel J. (1988) Food and breeding success of the Long-tailed Skua at Scoresby sund, Northeast Greenland. ARDEA 76 (1): 27-41
In 1973, 1974 and 1975, food and feeding habits of the Long-tailed Skua were studied at Scoresby Sund, Northeast Greenland. Attention was paid to the influence of lemming abundance, Arctic Fox predation, and other environmental conditions on egg production and breeding success. From stomach analyses it appeared that the average biomass consumed by territorial Long-tailed Skuas was made up of: terrestrial vertebrates (73%), berries (10%), marine animals (10%) and arthropods (7%). Transient birds consumed fewer terrestrial vertebrates (21%) and more marine animals (61%). Terrestrial vertebrate food in June consisted almost exclusively of Collared Lemmings; in July, juvenile Snow Buntings became important too. The male foraged more outside the territory and at sea and provided the young, if any, mote frequently with food than the female which foraged more in the centre of the territory and took more insects. The female usually joined the male bringing food to the young. Shortly after hatching, exclusively arthropods and young berries were fed to the young. Later main food biomass was made up of the Collared Lemmings and juvenile Snow Buntings. The latter started to fledge in the second week of the Long-tailed Skua Chicks. These terrestrial vertebrates were essential for the growth of the young and the Snow Bunting may playa role of similar importance as the lemming in the diet of the young. Lemming abundance in June, which is the period in which the lemmings are forced out of their snow nests, and which is also the pre-egg-laying period in the Long-tailed Skua, determined clutch size. When lemmings were not abundant, coastal breeders did benefit from foraging at sea and had a significantly larger clutch than birds breeding inland. In 1974 food was much less available than in 1973 and 1975, due to extremely long-lasting snow-cover and a low population of lemmings. No eggs were laid. In years with a moderate to high availability of lemmings, about 90% of the territorial pairs of Long-tailed Skuas produce eggs. This situation seems to occur in two successive years out of every four or five in Northeast Greenland. Once eggs had been laid, breeding success until fledging was negatively correlated with the extent of snow-cover and with the abundance of Arctic Foxes whose population was correlated with the lemming abundance in the preceding year.


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