The breeding season diet of white-tailed eagles in Scotland

The breeding season diet of White-tailed Eagles in Scotland was assessed from samples of food remains at nest sites, enabling spatial and temporal comparisons but likely underestimating smaller food items, soft-bodied items and fish. During the 20-year study, 293 samples from 92 different nest territories contained 11,375 food items, comprising 67% birds (70 species), 27% mammals (17 species) and 6% fish (at least 30 species). The types of foods in samples from individual territories were similar across years, even over the full length of the study. At coastal territories most food remains were from seabirds and fish. In other territories, various dominant foods included wetland birds, rabbits, lambs, hares and gamebirds. Regional differences reflected this, with marine items most prevalent in the Outer Hebrides, north-west mainland, Skye, Islay and Jura. Large mammals were common food items in Mull, Lochaber and mainland Argyll, and waterfowl were important prey on the Uists, Islay, Jura, Mull, Lochaber and mainland Argyll. Hares and grouse were predominant at nests further inland towards the east of Scotland. Most lamb remains were recorded in those territories first occupied after reintroduction, with progressively fewer in territories established thereafter so that by 2017, lambs were frequent (30% or more of recorded items) in only five of the 58 territories sampled. In retrospect, the previously widespread view that lambs are an important food for White-tailed Eagles has been superseded; the prevailing evidence now is that marine items (seabirds and fishes) are the most important breeding season food in Scotland. As elsewhere in their range, White-tailed Eagles in Scotland appear to be generalist foragers that take the most easily available local foods. Consequently, further dietary shifts might be expected as the population expands and more individuals settle in areas with greater access to the uplands or to rich freshwater habitats.