Cowbirds 'outsource' parenting duties

Q: Earlier in the summer I saw a very small bird feeding a much larger one. Is this something that happens — do some kinds of birds help out other species?

A: This does happen in the bird world, but not voluntarily. I'm almost certain you noticed a young brown-headed cowbird being fed by a much-smaller chipping sparrow, a scenario that occurs frequently during the summer. Cowbirds aren't nest builders, instead laying their eggs in other birds' nests, one egg per nest, essentially outsourcing parental duties.

The females keep an eye on the nests where they've deposited eggs, and if birds or humans remove a cowbird egg, the cowbird may return to destroy all the remaining eggs, thereby forcing the host birds to attempt another nest. This way, the cowbird can be certain that her egg will be first to hatch, giving a cowbird chick an advantage over the natural nestlings.

This practice is called nest parasitism and something like 150 species, from bluebirds to cardinals to sparrows, are victimized by it. The natural world has been dealing with nest parasites like brown-headed cowbirds for a long time. It may be uncomfortable to watch a tiny sparrow feeding a large juvenile cowbird, but it is part of nature.

Q: I read your column about the census of bald eagle nests, and it said that there would be a return trip to count the chicks in the nests. How many young eagles were counted on that second trip?

A: Good question: When John Moriarty from Three Rivers Park District returned to fly along the Mississippi River in June, he counted 51 chicks in 36 nests. He conducted the earlier count, that one of active nests, along the Mississippi National River and Recreation Area, Dayton, Minn., to Prescott, Wis., in April.

Q: A tiny bird has been singing its heart out on a daily basis — it's so small I can't get a good photo to send, but the song is loud, long and fluttery. The bird is brown and beige, can you help me figure out what kind it is?

Q: There was a pileated woodpecker at my suet feeder the other day, and it occurred to me to wonder: Where do these big birds build their nests?

A: Like all woodpeckers, pileateds use their beaks to chisel a hole in a dead or dying tree to hold their nest. If there's a woodland nearby, that's probably where their nest tree is located. Both the female and male pileated work on excavating the nest hole, and they share nesting duties, taking turns to incubate their eggs during the day, with the male handling night brooding duty. Once the eggs hatch, both woodpeckers hustle to bring back food for the young birds, and continue to feed them out of the nest for several months. The pileated visiting your suet might have been grabbing a meal for one of the youngsters.

Q: I put out feeders for hummingbirds, but other birds have been using them and one oriole, especially, is keeping the little birds away from the nectar. How do I keep hummingbird feeders for hummingbirds?

A: Diversifying is probably the best answer: How about setting out several nectar feeders, at different spots in your backyard, to increase the chances that hummingbirds can sip some nectar while orioles, woodpeckers and others are also enjoying a sweet treat.

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.