We’ve had a few odd looking birds in the yard this week, and it’s not just because I’m not accustomed to seeing pine grosbeaks. Among the largest flock of cardinals I’ve had in any of the places we’ve lived (five males and three females around the feeder at once!) is a female with little remaining upper mandible and a compromised lower mandible.
And here’s a likely first year female with a normal bill, for reference.
I suspect this is probably a result of avian pox, which attacks soft tissue and leaves warty lesions around exposed skin areas such as the eyes, legs, and bill surround. It can also damage adjacent tissue (such as the bill) and the effects are notable even after the virus has run its course.
This bird seems pretty healthy, so I suspect she’s finding a way to eat despite lacking much of her bill. I haven’t seen her at the feeder or accessing any other seeds, so I think she may be sticking to softer fruits around the neighborhood. She’s certainly at a disadvantage, and I wonder how she’ll fare this winter.
Avian pox can be spread by mosquitoes or by proximity to other birds. Though I haven’t seen her at the feeder, I’ll probably give the feeder station a thorough cleaning this weekend anyway.