Q: A pair of mourning doves nested in a spruce tree in our yard this summer. After a couple weeks of sitting on the nest, one of the doves walked out to the end of a branch with an egg held between its legs, then dropped it to the ground. Did the dove do this because the egg wasn't going to hatch? This seemed unusual to me.

A: I'm speculating here, but you may well be right, that the dove sensed one of its eggs wasn't viable. Or a brown-headed cowbird might have laid its egg in the dove nest, and the dove was getting rid of an interloper. Either way, it's fascinating behavior and I wish I had seen it.

Night sippers

Q: I sometimes filled our hummingbird feeder right before dark, but several times this summer the feeder was empty by morning. Would bats do this?

A: Tropical bats that live on fruit develop a taste for human-made nectar, but that's not a problem here: The bats that summer in our region are insect eaters, not nectar sippers. I'd suggest flying squirrels as a more likely culprit, or even night-roaming raccoons, if they can gain access to your feeder.

What's killing the birds?

Q: Some weeks ago as I was walking my dog I came across three dead songbirds not far apart on the ground. We also had two cases of goldfinches just sitting on the feeder, puffed up and very lethargic. What was going on?

A: Another reader sent a similar question, involving sick-seeming chickadees at her birdbath, and about the same time I was able to capture a 'dee unnaturally still, sitting on the edge of our birdbath. That bird ended up at the Wildlife Rehabilitation Center (where it later died), so I asked one of the staff veterinarians for her views. Dr. Leslie Reed noted that West Nile virus hit chickadees hard this year and affected other songbirds, as well. Even though we tend to think of the virus in terms of crows, it affects other species, too, and can be deadly. Reed was seeing many goldfinches and house finches with symptoms of avian conjunctivitis, including the swollen eyes and reddened skin that characterize this disease. If you spot sick finches at your feeders, please take them down, clean them thoroughly and wait at least a week before putting them back outdoors.

Small but tough

Q: The hummingbirds were very aggressive toward each other at my feeders late in the summer and into fall. Is this normal?

A: It's not at all unusual for ruby-throated hummingbirds to battle each other for ownership of a garden bed or nectar feeder. They're feisty little birds and territorial toward each other at all seasons. However, other readers report seeing crowds of hummingbirds at their feeders in the fall, so it can go either way: One very aggressive bird may drive off the others, or several may feed in peace, their need for energy trumping their competitive drive.

Keep it clean

Q: What's the best way to clean my bird feeders?

A: This question has been studied in depth and researchers report that a soak in a bleach solution is the best way to reduce salmonella and other bacteria on bird feeders. It's a good idea to take feeders down at least every couple of months, scrub them with soap and water, and then immerse them in a 9-to-1 water to chlorine bleach solution. Rinse feeders well and dry thoroughly before filling with seed. Birds tend to bunch up at feeders, something they don't do in the wild, so it's up to us to do all we can to stop the spread of disease in our backyards.

Suet schedule

Q: Is it OK to continue to fill the suet feeder during hot summer months?

A: During hot weather, the only kind of suet that doesn't pose potential harm to birds is in the form of rendered suet cakes or plugs. The fat has been heated so it doesn't melt as easily as raw suet would. Fat melting onto feathers is difficult for birds to wash off, leading to impaired ability to remain cool in the heat. In my own backyard, where we offer rendered cakes all summer long, it's very popular with birds and the cakes hold up well in the heat.

Note to readers: One caveat, if you're following my recent advice to keep garden stalks standing: If powdery mildew or other leaf diseases are a problem, go ahead and cut and dispose of plant stalks.

St. Paul resident Val Cunningham, who volunteers with the St. Paul Audubon Society and writes about nature for local, regional and national newspapers and magazines, can be reached at valwrites@comcast.net.