Posted by Bob Lefebvre
I feed birds in my SE Calgary yard and spend a lot of time watching them. Recently I saw something new – a bird with some really obvious large growths on it.
I wasn’t sure what this was at first but a quick internet search identified the problem as avian pox. This is a virus that comes in two forms, one of which causes these dry wart-like growths on the parts of the bird without feathers (feet, legs, base of the bill, and around the eyes). The other form affects the respiratory and gastrointestinal tracts. It’s a problem, and something to watch out for at your own feeders.
Avian pox is highly contagious and is transmitted by mosquitos, but birds can also become infected by by direct contact with infected birds. Birds can also get the virus indirectly through contaminated feeders or birdbaths, or even dust from the ground below these. Fortunately, the virus cannot infect humans or pets like cats and dogs (but is very dangerous to captive or farmed birds).
So what to do? This particular bird has obviously been infected for quite a while, and it can still feed, so it appears to be otherwise healthy. Such birds can survive the virus and the growths may drop off in time. The first thing to do to prevent spread of the disease is to immediately remove the bird feeders and birdbaths, which may be contaminated, and to clean them thoroughly in a 10% bleach solution. I had one heated birdbath and four metal tubes with tree nuts which I removed and disinfected (I also disposed of the remaining nuts in the feeders). I did not have a sunflower feeder up at the time. In the winter I spread sunflower seeds on ground which I have cleared of snow. The many Dark-eyed Juncos and our pair of Eurasian Collared-Doves prefer to feed this way. House Finches and House Sparrows, Eastern Gray Squirrels, and Magpies also feed on the ground. The tube nut feeders are used mostly by at least eight Northern Flickers who come daily, but are also frequented by a pair of Downy Woodpeckers, a few Red-breasted Nuthatches, and occasionally by Black-capped Chickadees. If no easy food is available on the ground, House Sparrows and Magpies willl do their best at the tube feeders, but get very little.
I put the feeders and birdbath away and stopped putting out sunflower seed too. Disinfecting the birdbath and feeders keeps them safe for about two weeks, but I wanted to make sure the bird wasn’t still around. Since I hadn’t seen it before, I thought it might be a one-time visit. After ten days I put the tube feeders and birdbath back out, but still did not feed the ground birds since that attracts magpies (and the ground could still be contaminated). A few days later, I saw the infected bird briefly, on the ground once again, so I removed the birdbath and disinfected it again. I continued to use the nut feeders, since I hadn’t seen this magpie, or any magpie, feed on there this winter. I saw the infected bird a third time in late March but not since.
March 9, 2026, Calgary. This Black-billed Magpie, infected with avian pox, constantly shook it head due to the large lesion there, and tried to wipe it off on the fence. Photos by Bob Lefebvre.
I hope I don’t see the infected bird in my yard again but of course it may be visiting other feeders in the area and possibly spreading the infection. I had been advised by the Calgary Wildlife Rehabilitation Society that I should try to capture the bird and take it to them, to remove it from the population while it heals. I could do this – I have a small animal trap that I’ve used for feral cats, and I have occasionally caught magpies while doing that. But the infected magpie rarely shows up, and meanwhile I would likely capture the regular local magpies, cats, and other birds if I put a baited trap out. For now I’ll wait to see if it returns.
To try to get an idea of how common this disease is in Calgary, I contacted The Wild Bird Store to see if they had heard of any cases of Avian Pox from their customers. They had not heard of any at all. On iNaturalist, there is only one other case reported in Calgary, a magpie that was badly infected in the NW last fall. You can see the photos of that bird here. (It doesn’t look like the same bird I saw and was miles away from my location.) So avian pox seems to be very rare in the city.
Please note that it is important to always disinfect your feeders and birdbath at least monthly, to prevent the spread of not just avian pox, but other diseases as well. A common one is conjunctivitius in House Finches, which I have seen in a bird in my yard as well (a few years ago).
More information about avian pox is here: Cornell University Wildlife Health Lab.
Information about conjunctivitis in House Finches. Also see Monitoring House Finch eye disease with Project Feederwatch.
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