A Sea Eagle.
Photo: Chris Johnson
October 19, 2001
This is Genevieve Johnson speaking to you from the Odyssey.
Darwin and its outlying areas are a haven for white-belied sea-eagles. These magnificent birds of prey are a part of a group of birds known as raptors, which includes all eagle, kite, falcon and hawks species. As a general rule, these birds can be found around the entire coastline of Australia, while here in Darwin they are particularly abundant. Unfortunately, the same cannot be said for other coastal cities where they are becoming less common due to continuing threats that include shooting, poisoning, excessive disturbance of breeding by urban development and the removal of significant patches of tall trees. There is also mounting concern over sea-eagles eating waterfowl found dead or crippled after having been shot by hunters, endangering the birds with lead poisoning.
White-bellied sea-eagles are actually giant kites, not true eagles whose lower legs are feathered. They are black and white underneath and grey on top. They sometimes nest on high cliff tops but appear to favour building their huge nests in the forks of trees as do most eagle species, which they line with leaves, grass and seaweed. These animals also like to use the treetops as a perch from which to hunt. One day, we had sea a eagle scanning for fish in the waters of Darwin harbor from atop the Odyssey's main mast. Piracy among sea-eagles is also common and we have watched them pursue defenceless gannets until a fish is regurgitated, much the same as the magnificent frigate birds we used to watch in the Galapagos Islands harassed the Boobies.
Most raptors hunt during the day, with the sea-eagle preferring to search along inshore waters, and over inland lakes and rivers for reptiles, fishes, sea snakes, water and other sea birds. A significant proportion of their diet also includes several pest species within Australia. Before receiving protection, many birds of prey were seen as pests when they were wrongly blamed for taking valuable livestock such as lambs, when in fact the real culprits were introduced foxes and feral cats. We have since realized that these birds feed on carrion and rarely attack live animals larger than themselves. They do however prey on several of our most menacing introduced species such as rats, mice, birds and rabbits, playing a crucial role in controlling the very species that have had such an adverse effect on this fragile natural environment.
To catch their prey, a sea eagle will glide over the water, scooping up their quarry from the surface. They use this 'glide and snatch' technique as they find it nearly impossible to take off from the water while grasping prey. The site of a bird plunging, its talons outstretched, snatching an unsuspecting fish is an exciting experience as well as an impressive display of strength and precision, considering the bird must allow for the refraction of light on water. Sea Eagles are able to account for light rays bending when they hit the water, meaning the fish is not actually where it appears to be when looking down. Tiny spikes on the soles of the feet assist in grasping slippery prey while the talons are used to drive through the vital organs. A wingspan of two meters, a large hooked beak and sharp hazel eyes complete the picture of this amazing creature.
Log by Genevieve Johnson