Tuesday, October 19, 2010

Cormorant spreads its wings

Yesterday afternoon as the dust settled from another exciting field trip with fourth grade students, ACEC Teacher Naturalist Carol Ward spotted a double-crested cormorant (Phalacrocorax auritus) on one of the floating islands in Deep Mill Pond. The cormorant was holding its wings out in spread-eagle fashion. This behavior is fairly unique to cormorants and is believed to help them dry their feathers. However, many birds dive underwater and don't exhibit this trait. One possible explanation is that cormorants don't have waterproof feathers the way that ducks do and must spread their wings out to dry in the sun and wind. If they had waterproof feathers they would be too buoyant to dive to great depths while hunting for fish. Recently there has been some debate as to whether the cormorants are holding their wings out in order to generate muscle heat in order to compensate for the chilling effect of cold fish in their bellies. See the Bird Forum discussion page HERE for more information on this debate.

Montana is the summer habitat for cormorants. This individual is on its way to wintering grounds along the Gulf of Mexico, anywhere from Florida to Texas. Usually the fall peak for cormorant migration is around September 6th, so this bird is on the tail-end of the migration period.

The cormorant earns its name "double crested" because of the double crest of feathers that are fully developed for only a short time early in the year. It is a black or dark-brown bird with a dull greenish or bronze gloss. It has orange-yellow skin on its face and throat that is distinctive throughout the year. They are fairly large birds (typical length of 70 - 90 cm with a body mass of 1.2 - 2.5 kg) with males that are slightly larger than the females.

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