White-tailed eagle only from the mainland. Also Rùm hosts large seabird colonies that make for viable prey, including eider, shag ("Phalacrocorax aristotelis"), auks and gulls; as well as one of the few in Britain of manx shearwater ("Puffinus puffinus"). Furthermore, mainly as a source of carrion, were a population of around 1500 red deer and 200 feral goats; otters and gulls were also numerous and available to kleptoparasitize. The birds to be used for reintroduction were gathered as nestlings from western Norway, as this is the nearest native breeding population. The young eagles were either kept in high grade fowl cages or
Procellariidae been implicated in (but not proved to have caused) the expansion in range of the northern fulmar in the Atlantic. Three of the six prion species have bills filled with lamellae, which act as filters to sift zooplankton from the water. Water is forced through the lamellae and small prey items are collected. This technique is often used in conjunction with a method known as hydroplaning where the bird dips its bill beneath the surface and propels itself forward with wings and feet as if walking on the water. Many of the shearwaters in the genus "Puffinus" and "Ardenna" are