Sunday, November 9, 2008

Avian pox?

Day two of FeederWatch 08-09, and the joint is jumpin,’ as though the birds had been lined up outside for days. The usual cast has been here, on and off, all day: Dark-eyed Juncos, Black-capped Chickadees, House Finches, Spotted Towhees, Northern Flickers, Bushtits, and a single, grumpy Song Sparrow.

I was watching this feeder-potato House Finch who had parked himself on the sunflower seed feeder, munching away, trying to keep all others from his stash. The grab-n-go chickadees were able to get around him by double-teaming.

I liked this picture for the defiant look from the finch, but then I noticed the large, dark blob on his right foot. My guess is that this bird has avian pox, a viral disease that in recent decades has become relatively common in House Finches in the western US and British Columbia. Among other symptoms, tumours form on unfeathered parts of the body –the legs, feet, bill, and around the eyes. These can cause loss of toes (which seems to have happened to the pictured bird’s left foot), or worse, make eating difficult or cause blindness, leading to death by starvation or predation.

The virus is transmitted by mosquitoes, and may also be passed from bird to bird in places of close contact, such as communal roosts or feeding stations. It is most often observed in fall and winter. It seems likely this is what this bird is dealing with. If large numbers of HOFIs continue to use this feeder along with this seemingly infected individual, I may be inclined to take it down, not wanting to help spread the virus.

Or maybe the rats will return and I’ll have to take it down anyway.

For more on avian pox, see here (Warning: unpleasant images).

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