The Eagle with the sunlit eye
The sight of a golden eagle soaring effortlessly above a high crag or along the side of a glen gives an added thrill to a day on the Scottish mountains. However it is now becoming much commoner to see Scotland’s other eagle – the sea eagle – specially along the west coast or the Hebrides.
The white-tailed eagle (Haliaeetus albicilla) or sea eagle was driven to extinction in Britain earlier this century. Now, thanks to a reintroduction programme run jointly by Scottish Natural Heritage and the Royal Society for the Protection of Birds, the sea eagle has returned to some of its former haunts.
The sea eagle is the fourth largest eagle in the world, and is our largest bird of prey, with a wingspan of nearly two and a half metres. By comparison, the golden eagle’s wingspan rarely exceeds two metres. The mature sea eagle has a greyish brown plumage with a pale head, reminiscent of its famous close relative, the bald eagle, national symbol of the USA. One striking feature is its yellow eye from which it gains a poetic Gaelic name Iolairesuilnagreine ‘the eagle with the sunlit eye’. Its beak and talons are also bright yellow.
The sea eagle only gains its characteristic white tail as becomes an adult. In flight, it appears rather like a huge vulture, with typically ponderous movements. When it soars its wings are held out flat and the tips often droop slightly.
As its name suggests, the sea eagle usually nests around coasts, but it in some parts of its range it may also be found near lakes and rivers further inland. The nest, or eyrie, is constructed of large sticks and branches. The eyrie must offer a clear view of the surroundings and provide easy access for the eagles themselves, but at the same time provide shelter and protection from predators which may steal their eggs or chicks.
Sea eagles sometimes begin displaying in October or November, but this becomes most intense in early spring. During courtship, the pair can perform daring aerodynamic feats, such as grappling talons in a mid-air cartwheel. They spend much of their time together, often soaring side by side or perched together on their eyrie. Their flight displays end quite abruptly once the eggs are produced. The two or three white eggs are laid in early spring and incubation, by both sexes, lasts 38 days. It is not uncommon for two chicks to survive amicably in the same nest. This is in contrast with the golden eagle, where the larger chick often deprives the younger sibling of food and only the largest may survive.
The sea eagle has a very varied diet. It feeds on fish, rabbits and hares, and a range of birds, including eiders, shags and auks. In the past, Shetlanders attributed the bird’s fishing ability to the supernatural. They believed that as soon as an eagle appeared fish would swim to the surface and offer themselves belly-up as a gesture of submission. In actual fact sea eagles are are quick to spot spent salmon on the spawing grounds, or take disabled fish forced up to the surface in deep tidal streams. Shetland fishermen also believed that smearing their own baits with sea eagle fat would improve their catches. Unlike the osprey which soars high above the water searching for prey and plunges in an awe-inspiring dive, the sea eagle tends to glide a few metres above the water before it descends to snatch the unsuspecting fish from the water with barely a splash. Although sea eagles are well able to catch live prey, they will often steal food from other predators such as otters, or follow fishing vessels in search of discarded scraps Sea eagles are also scavengers of carrion, particularly in the winter months.