Avian Pox

Last week a friend and I noticed a lone house finch staying quietly on the ground outside my front door when we walked outside. We stopped to watch it, and after a couple of attempts it managed to fly to a perch on the nearby tube feeder. I expected to see the crusted-over eyes of House Finch eye disease, mycoplasmal conjunctivitis, since we have occasionally seen birds with this debilitating condition, as I wrote about in 2010. However, this bird's eyes were not crusted-over or weepy, but one was greatly overshadowed by a warty-looking bump and there was another bump on its beak. (Now that I look at the 2010 photos, I can see a bump on that bird's beak too, which I didn't notice at the time.)

I consulted my ornithologist friend Dan Tallman, who pointed me to information about avian pox, sometimes abbreviated AVP. This is a disease that affects a wide range of both commercial poultry and wild birds. Warty growths appear on non-feathered areas of affected birds; there is also a variant that affects the mucous membranes and causes breathing problems. It's caused by a virus that can be spread by mosquitoes, by direct transmission between birds, and by contaminated surfaces like feeders. (More info: AVP and conjunctivitis in birds at feeders | Pox from a commercial fowl science perspective)

We've taken down the tube and hopper feeders the finches tend to use, to minimize the risk of transmission between birds at the feeders, and will sanitize them before putting them back up. It's a good practice to clean and sanitize (using a solution of nine parts water to one part bleach) bird feeders every couple of weeks, and if signs of illness are present, more often. Let them dry thoroughly before refilling. (More info: Tips on feeder maintenance)

House Finch Conjunctivitis

This poor little house finch has been hanging around our feeder area for long periods of time. It doesn't fly well and doesn't startle when we come outside -- just sits quietly. I was able to get quite close to take these photos. It appears to have an eye infection that is well known in house finches.

The Cornell Lab of Ornithology describes the condition:

Infected birds have red, swollen, runny, or crusty eyes; in extreme cases the eyes become swollen shut or crusted over, and the birds become essentially blind.  Birds in this condition obviously have trouble feeding.  You might see them staying on the ground, under the feeder, trying to find seeds.  If the infected bird dies, it is usually not from the conjunctivitis itself, but rather from starvation, exposure, or predation as a result of not being able to see.

Although infected birds have swollen eyes, the disease is primarily a respiratory infection. It is caused by a unique strain of the bacterium Mycoplasma gallisepticum, which is a common pathogen in domestic turkeys and chickens. The infection poses no known health threat to humans, and had not been reported in songbirds prior to this outbreak. Researchers at various institutions are currently trying to learn more about the transmission, genetics, and development of this disease.

Conjunctivitis was first noticed in House Finches during the winter of 1993-94 in Virginia and Maryland. The disease later spread to states along the East Coast, and has now been reported throughout most of eastern North America, as far north as Quebec, Canada, and as far south as Florida. It has also appeared in some species other than House Finches.

Advice from the Cornell Lab for people observing infected birds at their feeders:

1. Space your feeders widely to discourage crowding.
2. Clean your feeders on a regular basis with a 10% bleach solution (1 part bleach and 9 parts water) and be sure to remove any build-ups of dirt around the food openings. Allow your feeders to dry completely before rehanging them.
3. Rake the area underneath your feeder to remove droppings and old, moldy seed.
4. If you see one or two diseased birds, take your feeder down immediately and clean it with a 10% bleach solution.

 I'm going to follow this advice!