Did You Know
Purple Martin Pair at House
Photo Credit: Jim Williams
Ruby-throated Hummingbird
Photo credit: Jim Williams
American Robin
Photo credit: Rebecca Field
Gray Catbird with worm
Photo credit: Jim Williams
Q. I put up a 16-hole house for purple martins but haven’t had any takers, even though I keep the sparrows out of it. Someone told me that a disease on their winter grounds killed most of the martins off. Is this true?
A. I haven’t heard of any purple martin die-off, but what I have heard is that it’s a challenge to attract martins to set up housekeeping in a new house. It would be worth your while to check out a couple of the web sites devoted to martins. They’ll fill you in on things like dawn song tapes to help attract these beautiful birds: http://purplemartin.org and http://www.mnmartin.org.
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.
Q. Our bird house has been very successful this season. First chickadees raised a family, then wrens moved in. The wrens are just about ready to leave and sparrows are perching on the box. Are the sparrows waiting to occupy the house when the wrens leave?
A. It’s lucky that the wrens waited for the chickadees to fledge, since wrens are usually much more impatient and will puncture eggs or kill the youngsters in order to take over a nest box. Now that sparrows have discovered the box, the wrens may be in danger themselves, since sparrows are notorious for killing nestlings and even adult birds in order to claim a nesting cavity. The best defense is an the entrance hole that is too small to admit sparrows. If it’s larger than 1 1/4 inches in diameter you might want to buy a metal piece at a wild bird store to narrow the hole, in order to keep out sparrows.
Q. We have two cardinals coming to our feeder and they seem healthy except that both 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 but probably are going through the molting process. 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. These “baldies” make it easy to see that birds evolved along the reptile side of the animal kingdom.
Q. I was interested in the recent piece on how birds learn to sing, but what I want to know is how they sing. Do birds have a voice box or something else that allows them to make such sounds?
A. Birds do have voice boxes, just as we do, and the vibration of air through the walls of the voice box is what creates their songs. There’s at least one major difference: where humans have a larynx located at the top of the windpipe, a bird’s voice box, or syrinx, is located farther down, where the trachea branches out. Birds can change pitch and volume by manipulating muscle tension within the syrinx and the speed of the air moving through it. Some birds, such as veeries and hermit thrushes, make two sounds at once, resulting in a haunting, echo-like sound.
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. Robins (and other 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.
Q. Even when I put out fresh sugar water, the hummingbirds won’t feed at my feeders. They hover for 10 seconds or so and then flit away. How can I get them to stick around?
A. Something is discouraging your hummingbirds and if the sugar water is fresh, then I’d suspect that insects are the problem. Do you see bees, wasps or ants around the feeder? Wasps, especially, frighten off hummingbirds. If ants are a problem, it’s a good idea to hang a water-filled ant moat above the feeder. If bees and wasps come in for the sugar water, try switching to a saucer-style feeder — these keep the solution too far away for the insects to reach.
Q. Robins raised a family on the nesting platform I put up for them. Now that they’re gone, should I remove the nest they built?
A. I’d leave the nest alone for now. Robins, and some swallows and phoebes, incorporate mud in their nests, which makes for a very sturdy structure. They may reuse the nest this season, adding some grass and leaves to freshen it up for their next brood. At the end of nesting season, though, you could take the nest down.
Q. My friends and I noticed a paucity of birds at our feeders in late spring and they’re just now starting to return. Any explanation?
A. The same thing is happening in my backyard, with greatly reduced bird traffic at feeders until about mid-June. The reason: this is the time of year when nearly all songbirds ignore seeds, switching instead to an insect diet. They feed their offspring exclusively on insects, especially juicy caterpillars, for the big dose of protein they provide. On this diet, young birds mature quickly and leave the nest in just over two weeks after hatching. This is necessary because predators are always watching for a tasty meal. Once the youngsters leave the nest, the whole family may show up at your feeders.
Q. Are birds color-blind?
A. Just the opposite, birds are highly sensitive to color, more so than humans. The fact that birds are so brilliantly colored is proof that color is important to them. They use color to discern which birds would make good mates, how healthy another bird is and which birds are youngsters needing some guidance. Birds see a broader spectrum of color than we do and they’re able to see some ultraviolet light, which we can’t.
Q. I saw a bald eagle land near an ice-fishing hole on a city lake, when it was still all frozen up. Do eagles eat fish in winter, or only when there’s open water?
A. Eagles eat fish all year round, and can and do fly long distances to find open water for fishing. In the metro area, eagles bunch up at open areas on rivers near power plants. Eagles occasionally snatch injured ducks and they’ll also scavenge on road-killed deer.
Q. I just saw the strangest thing on my backyard maple tree—the bark seemed to be moving! When I looked more closely it turned out to be a bark-like bird, but I don’t know what kind.
A. That’s an excellent description of the brown creeper, which does look like a piece of bark as it spirals upward around a tree trunk in search of insects. The creeper is perfectly camouflaged, with its brown back over an all-white belly. Creepers invariably move upward and their cousins, the white-breasted nuthatches, move downward on tree trunks. Each may find hidden insects that the other’s feeding strategy has overlooked.
Val Cunningham, who writes about birds for many publications, is also a field trip leader for St. Paul Audubon and conducts IBA and Breeding Bird Atlas surveys. A version of this piece appeared first in the Minneapolis StarTribune.