Monday, September 6, 2010

Pigeons, Windows, and Ectoparasites

Warning: This post is not for the squeamish. It contains graphic photos of a dead pigeon.

Pigeons or technically Rock Pigeons (Columba livia) are ubiquitous in the urban environment of temperate latitudes. Its natural habitat is open and semi-open environments with cliffs, usually on coasts, in western and southern Europe, North Africa, and into South Asia. The urban environment provides similar cliff-like structural elements on buildings as well as abundant food sources (don’t feed the pigeons). I’m not a big fan of pigeons but I can appreciate their adaptability.

Window strikes kill between 100 million and 1 billion birds in North America each year (David Malakoff, Audubon magazine, March 2004). Because glass is transparent and reflective, the birds see a reflection of the outdoors and try to fly through what looks like unobstructed open space. Like a science fiction force field, they are immediately repelled. We have birds occasionally strike the windows of our home, most recently a Red-breasted Nuthatch (Sitta Canadensis), who did recover but remained dazed on the ground for more than a few minutes. Some birds do not recover and it’s always a sad moment when this happens.

I had some field work last week at a vacant car dealership, the kind of place with large showroom windows and the perfect environment for pigeons. Below the large windows, I noticed a dead pigeon on the ground with a trail of dried blood trickling from its beak.

It was an obvious window strike. If you look close at the next photo, you can see the faint impression of two bird strikes on the window. The impression shows the body and outstretched wings in flight.

I took a close-up photo of the pigeon’s head. I could see a few specks but without my geezer glasses they were just specks. When I downloaded the photo, I noticed that some of the specks were actually insects, bird lice.

The next photo is an extreme enlargement showing one of the lice.

Pigeons, and probably most wild birds, harbor an attractive mix of ectoparasites. The one in the enlarged photo is likely a slender pigeon louse (Columbicola columbae). The slender pigeon louse belongs to a group of lice known as chewing lice, specifically to the Superfamily Ischnocera, who feed on the downy part of feathers and softer fur. The slender pigeon louse eats the fluffy parts of the pigeon’s feathers. Think about this the next time you’re inclined to feed pigeons.

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