Wednesday, September 14, 2011

Cormorant Washing Line

Cormorant, Phalacrocorax carbo
The Cormorant (Phalacrocorax carbo) is one of the largest seabirds in Ireland, and also one of the most familiar. It can often be seen feeding in estuaries and perched in trees, where they sometimes breed (1). With its dark body and long, hooked bill it could be mistaken for its relative the Shag (P. aristotelis). However, the Shag is a smaller bird by about 20 cm and is rarely seen inland. Adult Cormorants have an attractive blue-green sheen to their plumage, a yellow and white bare patch of skin on its face and a white thigh patch that disappears after the breeding season (1).
Cormorant, Phalacrocorax carbo
Recently, I observed a Cormorant perched on an old mooring post in a river estuary. It held its wings out from its body in a drooping fashion that is known as a spread-wing posture. Many birds engage in this type of behaviour. Cormorant feathers retain moisture when diving for food, which decreases buoyancy and aids underwater pursuit of prey. Only the outer layer of feathers are wettable however, and a a layer of insulating air is maintained next the skin when diving (2). Yet the outer feathers remain wet upon emergence and therefore need to be dried. Hence the spread-wing posture (as seen in the photographs) of the Cormorant, a living washing line.

  1. Sterry, 2004. Collins Complete Guide to Irish Wildlife p. 34.
  2. Elowson, 1984. The Auk 101 pp. 371-383

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