Q: There's been a white swan on our small pond for several weeks. It doesn't appear to be injured, but we are concerned that there might be something wrong with it. Is this unusual behavior for a swan?

A: I asked Madeleine Linck, a knowledgeable naturalist at Three Rivers Park District and local liaison for the Trumpeter Swan Society, for her take on the lonely swan. She says that your midsummer sighting makes it likely that it's a trumpeter swan. The bird might have been molting new feathers and temporarily unable to fly or might be a young bird seeking out a new, temporary home. If the swan holds its wings up close to its body, then they're probably not injured, and if it doesn't seem weak and lethargic (symptoms of lead poisoning) it's probably healthy and should eventually fly off. Linck also noted that Minnesota now has about 6,000 trumpeter swans, an amazing success story for a bird once driven out of the state.

High-rise hazard

Q: You recently advised a reader how to get more birds to visit his 20th-floor balcony. I'd like to point out that birds poop whenever they feel like it — just look at your car. So what happens to the guy who lives on the 19th floor?

A: You make a good point and I neglected to consider this aspect of feeding birds in my response to the reader on the 20th floor. But in my experience, most birds — with the exception of goldfinches, starlings and mourning doves — don't poop right where they eat. If you can keep the latter two species, especially, away from feeders, you shouldn't have much of a mess.

Bird or bug?

Q: I was very excited to see an unusual bird among the petunias. My daughter looked it up on her smartphone and says it was a hummingbird moth. Is it a bug or bird?

A: Even though it acted very much like a hummingbird, your visitor definitely was an insect, a hummingbird clearwing moth. Many of us mistake these beautiful moths for hummingbirds, since their behaviors are so similar: The moths hover at flowers to draw up nectar through their long, thin proboscis, which resembles a long tongue. They're named for their transparent wings, which create a humming sound as the insect flies. Look for these moths among the bee balm, phlox and honeysuckle during the summer.

Telling loons apart

Q: Can loons be identified by their vertical neck patterns, and could researchers tell them apart this way, without having to band them?

A: This is a very interesting question, and I turned to Carrol Henderson, who heads up the DNR's Nongame Wildlife Program, for the answer. "Yes, the necklace markings on loons often have distinctive aspects that would allow a person to tell them apart, but I don't know that it's been used as a research tool," he said. Henderson says that it's not known whether the necklace stays the same through yearly molts as the bird ages. For the answer to your question, a researcher would need to study the necklace markings on leg-banded loons over some years.

Oriole retrofit

Q: Orioles have been visiting my hummingbird feeder and have pulled out the yellow bee guards from the drinking holes. Now it's easy for them to drink, but is this bad for hummingbirds?

A: What smart birds your orioles were, to remove the impediment to their drinking the sugar water in your feeder. I don't see that this will be a problem for hummingbirds, and in fact, the orioles may have done everyone a favor. It never ceases to amaze me that manufacturers continue to sell nectar feeders with yellow plastic flowers or rings they market as "bee guards," when yellow is the color seen most easily by bees and is a considerable attractant.

Mystery song

Q: I've been hearing a bird song for some years but have been unable to identify it. The song is a very melodic "deedle" sound, usually repeated as "deedle, deedle." It sings from hiding and if I approach its tree it goes silent. I've seen blue jays in the area, but have listened to many recordings of blue jay songs and did not find this sound. Any suggestions?

A: You've written an excellent description of the sounds made by your mystery bird, and I think you've answered your own question. My first thought was blue jay, since this is one of the many calls this species makes. If you can bear to listen to one more bird tape, try the fourth one on this site: www.allaboutbirds.org/guide/blue_jay/sounds. I hope you catch a glimpse of the singer soon.

House for finches?

Q: I'd like to put up a birdhouse for some of the goldfinches that visit my feeder, but don't know what kind to get.

A: You needn't invest in a nest box for these little finches, because they simply wouldn't use it. Goldfinches, like the majority of songbirds, build nests on a tree twig or shrub branch. They're what's called "outside nesters," as compared with the few species of birds that are "inside nesters," building nests in holes in trees, fence posts and other openings. These birds, including chickadees, bluebirds, tree swallows, great-crested flycatchers, woodpeckers, nuthatches and a few others, will adapt to human-made nest boxes because these approximate the conditions of a tree cavity or other natural sites.

Loon dance

Q: The loons Up North near our cabin seem to be holding social gatherings each morning. Loons fly in and join the pair on our lake, circling each other and flapping their wings, and this can go on for an hour. I'm mystified about what is going on.

A: Even though loons are highly territorial birds and will fight, sometimes to the death, to hold a good nesting lake, they also seem to become a bit social during the summer, even if the resident pair has a chick or two to protect. Loons will fly to a nearby lake and rendezvous with the resident loons, swirling in a slow circle, diving and flapping their wings if the tension starts to build. No one is quite sure of the reason for these loon "square dances," but it may have to do with the visiting loons prospecting for a nesting lake for the next year. They're not currently trying to usurp the resident loons, so things remain fairly peaceful. It must be quite a stirring sight to see.

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 val writes@comcast.net.