Tuesday, 25 January 2011

Yellow-billed loon

Gavia adamsii

Photo by Fredrik Salin (Internet Bird Collection)

Common name:

Order Gaviiformes
Family Gaviidae

They breed in the Arctic, in Russia, Alaska and Canada. They mostly winter at sea, along the coasts of Norway, western Canada and northern Japan, but also sometimes in inland lakes.

This large loon is 76-97 cm long and has a wingspan of 135-160 cm. They weigh 4-6,5 kg.

The yellow-billed loon mostly breeds on freshwater pools, lakes or rivers in the Arctic tundra, showing a preference for deep, clear lakes with stony or sandy substrates where water levels do not fluctuate. they prefer lakes where the water does not completely freeze, which have dependable supplies of fish and which have highly convoluted shorelines and aquatic vegetation providing habitats for fish and sites for nesting and brood rearing. Outside the breeding season the species inhabits inshore waters, fjords with muddy substrates and inlets along sheltered coasts, generally avoiding ice-covered waters.

They mostly eat fish, namely Cottidae, Microgadus proximus and Gadus morhua, as well as crustaceans, molluscs and marine annelids.

Yellow billed loons start nesting in June-July. Both sexes build the nest, a small depression in a mound of plant matter or turf, constructed on dry land near the water edge. The female lays 2 eggs which are incubated by both parents for 27-28 days. Chicks are dry and active within hours of hatching; brooding by both parents occurs in nest for about 3 days, then little on-shore brooding after about 9 days. In some areas, chicks 9-16 days old observed riding on parents back. Adults forage to feed young for up to 45 days.

IUCN status - NT (Near-Threatened)
Although they have a very large breeding range, the population is currently estimated at just 16.000-32.000 individuals, and is suspected to be undergoing a moderately rapid population decline owing to unsustainable subsistence harvest. This species is also vulnerable to oil spills in both its breeding and wintering ranges, and may be threatened by oil development activities on its Alaskan breeding grounds. These threats are exacerbated by a low reproductive rate and very specific breeding habitat requirements.

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