Eagles are indeed eagle-eyed

Q: Do bald eagles have good vision? When I see them, they’re usually sitting in a tree and looking around. Are they watching for prey?

A: We’ve probably all heard the expression, “eagle-eyed,” to describe someone able to spot things at a distance. Bald eagles can see farther than humans (a lot farther), their focus is much sharper and they see much more detail than we do. They have superb color vision, a broad range of focus and they can see almost 340 degrees around themselves, and they see ultraviolet light. There are many inflated claims on the internet about how far eagles can see, but generally these raptors are looking for movement, such as a rabbit, squirrel or fish in motion. Even when soaring overhead, they’re observing things on the ground. So, yes, eagles do have excellent vision that is far superior to humans’ visual skills.

Q: Walking through my local park in September I came across an arresting sight: There were eight flickers on the ground and a few more in the trees nearby. What brought them together?

A: The flickers you noticed were gathering for fall migration, which takes place from September through November, with a peak in late September. At this time of year, they’re often seen in groups and can be very vocal, giving their distinctive “kyeer” call, or a repeated call that sounds like “wicka-wicka.” It’s not surprising that you saw these handsome woodpeckers on the ground, since their favorite foods are ants and beetles. Hear Northern flickers here: allaboutbirds.org/guide/Northern_Flicker/sounds

Q: I hardly saw any chickadees all summer long, but in the fall a couple are showing up at my feeders again. What’s the explanation for this?

A: I’ll bet most of us who feed birds noticed a similar thing — no chickadees after late May or early June, and now they’re back, zipping around feeders and adding their energy to the backyard scene. The reason we don’t see them at our feeders for much of the summer is that they’re raising their brood of youngsters on a diet of insects. Like nearly all songbirds, chickadees switch to an all-insect menu during nesting season because this high-protein diet ensures that young ‘dees grow quickly and can leave the nest after only a few weeks of care. Once the young are out and about, parent birds and youngsters will visit our feeders.

Q: Several weeks ago I was at our cabin and turned on the Merlin app while I sat on the deck.

A: Good question, and you’re right, ruby-throated hummingbirds don’t really have a song. The Merlin app must have been picking up on a hummingbird’s twittering squeaks. The species makes these sounds when agitated, possibly at the sight of another hummingbird or an encroaching bee or wasp at a feeder, and sometimes during courtship. If you’re near a hummingbird you may hear the distinctive hum as they rapidly beat their wings, up to 80 times per second. Hear hummingbird sounds here: www.allaboutbirds.org/guide/Ruby-throated_Hummingbird/sounds.

Q: I seem to have a lot of house finches at the feeders all of a sudden, and one of them doesn’t look healthy. It huddles down in the feeder for minutes at a time and its eyes are swollen. What’s going on?

A: It sounds as if the finch is suffering from a bacterial disease that’s very prevalent in finches, avian conjunctivitis, also known as house finch eye disease. The Cornell Lab of Ornithology has studied this disease in house finches for three decades and finds that it gets passed from bird to bird, often at feeders, and increases dramatically in the fall. To control the disease, you should take down any feeders the finch visits and wash them thoroughly, then let feeders dry before refilling them. Raking the ground beneath the feeders to get rid of old seed and droppings is a good idea. This is a serious disease that often leads to death in birds, so if you have many finches coming to your feeders and notice the disease in several birds, the Cornell Lab recommends taking down feeders for two or three weeks, until the flock disperses.

Q: This year, for the first time, we have elderberry bushes in the backyard. We didn’t plant them, and wonder how they got here? Also, what is the gray bird that was eating the berries in early September?

A: Birds plant elderberry bushes whenever they poop the seeds after eating the fruit, possibly eaten in a neighbor’s backyard. And these plants offer lush purple berries for fruit eaters, especially the gray catbirds you observed. The only downside to elderberry shrubs, in my book, is their tendency to spread, but this can be controlled by removing plants.

A: Those are two excellent questions, and let’s start with the “lazy” claim. No birds are reliant on our feeders for all their daily calories. Instead, the birds we see consuming our seeds, peanuts and suet are still getting the majority of their food out in the wild. Feeder food is a supplement to wild food, but on days with extreme weather (cold, ice) when natural food is hard to find, feeders offer a welcome respite. So feeders don’t make birds lazy.

Cooper’s hawks do feed on small songbirds and it might seem that birds gathering at feeders make it too easy for the hawks. However, studies show that predation is lower at feeders than in the wild. This is probably due to the fact that as birds gather at feeders there are more eyes watching for danger and they’re quick to sound an alarm if a hawk shadow breezes by. Think how many times you’ve seen all your feeder birds scatter to hide in trees and shrubs — they do this many times a day out of a healthy fear of predators.

Q: When are the juncos due to return? I like these little charcoal-colored birds that are outside in all kinds of weather.

A: I’m glad to learn that you appreciate these hardy little sparrows that are a cheering sight as they hop on the snow in the deep of winter. In the southern half of the state, you can count on juncos flying down from the north sometime in September or October, after spending the summer in northern Canada or Alaska.

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