Racing divers
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Racing diver ( Aechmophorus occidentalis ) |
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| Aechmophorus occidentalis | ||||||||||
| ( Lawrence , 1858) |
The western grebe ( Aechmophorus occidentalis ) is a bird art from the family of grebes (Podicipedidae). Of the two subspecies described, A. o. Occidentalis occurs in western North America, A. o. Ephemeralis in central Mexico.
features
When fully grown, racing divers reach a body length between 51 and 74 centimeters and a weight of 550 to 1225 grams. The birds have no sexual dimorphism , have black and white plumage and a long, slender neck. Their beak is a dirty yellow. They can be distinguished from the related Claret divers ( Aechmophorus clarkii ) by their darker facial feathers .
Way of life
Racing divers live mainly in bodies of water with large open water areas; in winter they prefer brackish and salt water and move to the American Pacific coast. They eat 80 to 100% of fish and are also able to swallow large fish up to 20 cm in length. They also eat aquatic insects, especially rowbugs , molluscs and crustaceans, amphibians and, by the sea, worms. The food is usually captured by diving. The birds are able to stay under water for 30 s. Food is mainly sought during lunchtime, when the sun is high in the sky and visibility underwater is good.
Reproduction
The birds lay their eggs in the United States from May to July. They breed in colonies, some of which can contain over a thousand nests, often mixed with Claret divers. They are known for their striking courtship , which in many ways resembles that of the great crested grebe. A part of the courtship ritual, in which both birds run side by side across the water in triple steps, is particularly spectacular. The courtship also includes a courtship dance in which each of the birds dives for aquatic plants and holds them up while turning back and forth in front of their partner.
Usually three to four eggs are laid and incubated for 21 to 28 days. The hatched young birds have gray down. The head and underside are white. They lack the striped drawing typical of most grebes. Both parent animals are involved in raising the young. Similar to the black-necked grebe and the great crested grebe, the parents carry their young on their back for the first two to four weeks. Young birds are fed by their parents until they are around 70 days old.
Stock situation
As with the great crested grebe, the racing diver's plumage was processed in the fashion industry in the 19th century. This has contributed significantly to the decline in their populations as they were hunted intensively for it. The stock is now considered not endangered, even if it is still threatened by environmental pollution and habitat loss.
literature
- Josep del Hoyo et al .: Handbook of the Birds of the World. Volume 1: Ostrich to Ducks. Lynx Edicions, 1992, ISBN 84-87334-10-5 .
Web links
- Aechmophorus occidentalis in the endangered Red List species the IUCN 2008. Posted by: BirdLife International, 2008. Accessed January 31 of 2009.
- Videos, photos and sound recordings of Aechmophorus occidentalis in the Internet Bird Collection