|Habitat and Ecology:
Behaviour The European Shag is a coastal species that shows high nesting site fidelity. It feeds exclusively diurnally, and one bird is always present with the clutch or brood during the breeding season. The species breeds in colonies (del Hoyo et al. 1992) that can hold more than a thousand well-spaced pairs (Snow and Perrins 1998, Nelson 2005). It is largely sedentary (del Hoyo et al. 1992), although immatures may undergo post-breeding dispersive movements over short distances (del Hoyo et al. 1992). Some birds undergo short-distance migrations during winter. Individuals often forage alone when away from nesting colonies and in winter (del Hoyo et al. 1992, Snow and Perrins 1998), but may follow dense shoals of fish in flocks of several hundred individuals (Nelson 2005). Habitat It occupies marine habitats but does not usually occur far from land (del Hoyo et al. 1992). It shows a strong preference for rocky coasts and islands (del Hoyo et al. 1992) with adjacent deep, clear water (Nelson 2005), and forages over sandy and rocky seabeds (del Hoyo et al. 1992). It also prefers sheltered fishing grounds such as bays and channels, although it generally avoids estuaries, shallow or muddy inlets and fresh or brackish waters (Wanless and Harris 1997). Diet The species feeds on a wide range of benthic, demersal and schooling, pelagic fish. Sandeels (Ammodytidae) are the dominant prey of birds in British and some Spanish populations (Wanless et al 1997, Velando and Friere 1999, BirdLife International 2000, Velando et al. 2005), and are consistently present in the species' diet in most other locations studied. These are usually caught at, or near, the sea bed (Wanless et al 1997). Other prey species include fish of the families Gadidae, Clupeidae, Cottidae, Labridae, and Trisopterus spp. (del Hoyo et al. 1992), although birds also take small numbers of polychaetes, cephalopods, other molluscs and small benthic crustaceans (Wanless and Harris 1997). Adults provision their chicks with sandeels, but consume a broader variety of prey for themselves (BirdLife International 2000). The Mediterranean subspecies feeds mainly on coastal fishes, caught from the bottom or mid water over rocky or sandy seabeds, but economically important fish seem to form a very small part of the diet (Aguilar and Fernandez 1999). Breeding site The nest is constructed of marine vegetation and flotsam (del Hoyo et al. 1992, Nelson 2005), from just above the high water level to over 100 m high (Snow and Perrins 1998) on ledges, in crevices or in caves on sea cliffs, rocks and stacks, and at the base of sea cliffs amongst boulders (del Hoyo et al. 1992). Foraging range At Islas Cíes, Spain, birds foraged within 20 km of the colony all year round (Velando et al. 2005). During the breeding season, the foraging range was typically within 4 km of the colony, and birds foraged in groups of 300-1000 individuals (Velando et al. 2005). Foraging areas tend to coincide with areas of sandy benthic sediment (Wanless et al 1991, BirdLife International 2000, Velando et al. 2005), and occur where depth is less than 80 m (Wanless et al 1991, Velando and Friere 1999). At the Isle of May, Scotland, over 90% of foraging occurred within 13 km of the colony, and the maximum distance recorded was 17 km (Wanless et al 1991). Foraging individuals visited more than one area during a trip, often feeding at sites several kilometres apart (Wanless et al 1991). Birds were often found feeding in areas of strong tidal flow (Wanless et al 1991). The available data on European Shag feeding habitat suggest that, within the inshore zone as a whole, the species is fairly plastic in its habitat requirements. In some areas, the birds' foraging range is considerably less than 20 km; the small number of birds breeding at Hirta, Scotland, all appeared to forage within a 2 km radius (BirdLife International 2000). Similarly, birds were only present within 3 km of North Rona, Scotland (BirdLife International 2000).