Ulrike Kubetzki

Nests With a View: Distribution, Nest Habitats and Diets of Roof-Breeding Common Gulls (Larus canus ) in Northern Germany

Abstract The Common Gull (Larus canus) is a typical breeding bird species of the Baltic Sea coast in Schleswig-Holstein, northern Germany, where it has declined substantially in recent decades. Since the mid-1990s, Common Gulls have started to colonize flat roofs of buildings, consisting mostly of gravel and small stones. The total number of roof-breeding Common Gulls in Schleswig-Holstein is estimated to be at least 400-450 pairs for the period 2000-2005, with further increasing trends. Minimum reproductive performance at two colonies in 2000 was 0.9 and 1.8 fledged chicks per nest. The diet at two colonies studied in July 2001 consisted mainly of terrestrial food items. The most important prey categories were cherries, lumbricids, insects and bivalves. It is concluded that Common Gulls show a flexible response to environmental conditions by successfully exploiting a new breeding habitat, by reproducing successfully there and by taking benefit of their wide food spectrum to exploit man-made sites.

Adult Gannet migrations frequently loop clockwise around Britain and Ireland

ABSTRACT The Gannet Morus bassanus is one of the seabirds considered most at risk from collision mortality at offshore wind farms in UK waters, so a better understanding of migration routes informs assessments of risk for different populations. Deployment of geolocators on breeding adults at the Bass Rock, Scotland, and Skrúður, Iceland, showed that the timing of migrations differed between populations, birds from Bass Rock passing south through UK waters mostly in October and back in February while birds from Skrúður passed south through UK waters mostly later, in November, but returned north earlier, in January. Many birds from both colonies made a clockwise loop migration around Britain and Ireland. Only a minority of birds from the Bass Rock returned northwards to the colony through the southern North Sea. A counter-intuitive consequence is that many Gannets moving northwards through waters to the west of Britain and Ireland in spring may be birds from North Sea colonies. Although Gannets normally remain over the sea, one tracked bird appears to have made a short overland passage in spring from the west of Scotland through central Scotland to the Bass Rock, whereas most returned around the north of Scotland.