Q We have two cardinals coming to our feeder and they seem healthy except that their heads are completely bald. It looks rather grotesque, and I'm wondering if they might have some sort of disease.
A This is the time of year for reports of bald cardinals and blue jays. Your birds aren't diseased; they're probably molting.
For some unknown reason, a few birds lose all their head feathers at once, instead of molting in staggered fashion, like other birds. The head feathers invariably grow back, but it is a bit disconcerting to see these beautiful birds looking so unhandsome.
Twin beaks Q I was fortunate enough to find a hummingbird nest and have been keeping an eye on it as the baby birds grow up. Will the dominant youngster push out the other one so only one survives?
A You're lucky to be able to observe a hummingbird nest -- from a distance, I'm sure. I don't think you need to worry about siblingcide in hummingbirds. Most female hummingbirds lay two eggs and unless disaster strikes, both twins grow up and fledge from the nest.
Disappearing act Q My dog got fairly close to a robin's nest along our fence line, and the robins were very agitated, although the fence kept the dog away. Later we noticed that the nest was empty and wondered if the parents moved the baby birds.
A Birds don't move their nestlings -- when the young birds leave the nest it's under their own power. It's possible that the youngsters were just old enough to fly away from the perceived danger posed by your dog.
The other possibility is a sadder one: Your dog may have provided a scent trail for another predator, possibly a cat or other mammal, to use to find the nest and eat the young.
