Ask Maine Audubon: Intruders at your bird house? Sit back and enjoy them - Press Herald

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The house wren takes a different approach than other cavity-nesting birds when it comes to claiming bird houses, with the male arriving a week or two before the female. Nick Lund photo/Maine Audubon

Putting up bird houses is one of the best ways to help birds, at least those species that need cavities to nest in, but can’t create them on their own. This includes species like Eastern bluebirds and tree swallows, but also black-capped chickadees and house wrens.

However, we often hear from folks who are attracting nesting birds that they didn’t want, as is the case for Madge Baker from Shapleigh, who wrote in because of some house wrens. Madge says, “These energetic, pesky birds have run off nesting bluebirds two years in a row.” Let’s take a look at what wrens are up to and how they differ from some of our other cavity-nesting birds.

A key difference between house wrens and other bird house-nesting birds is the way we see them claim the boxes. Bluebirds will move around as pairs, visiting boxes in what seems like the Goldilocks technique, trying to find one that is just right. House wrens, on the other hand, have a very different technique: males arrive a week or two before the females, and will claim as many cavities as they can, going around and filling them with sticks. Then once the female arrives, it is her job to select which site she wants to nest in. Together they’ll build the nest that they will actually use for laying eggs and raising young, but that leaves behind many unused dummy-nests.

Madge also asked if there were any “legal steps (they) could take, or should (they) just sit back and enjoy the chutzpah and loud self promotion?” Since the house wren is a native species, there isn’t anything wrong with this behavior; they are doing what they’ve always done. And from the legal perspective, house wrens are protected by the Migratory Bird Treaty Act so if you don’t want to break federal laws, it is best to try to enjoy those loud bubbly wren songs!

WHAT’S UP WITH THAT WOODPECKER?

As we move through the summer, some adult birds just aren’t quite looking their best. They have the same look as new parents – sleep deprived, working hard, no time for self-care in months. In birds, this presents usually as feathers being worn, or sometimes off-color. This is what Steve Myers of Cape Elizabeth noticed and wrote in, saying he was seeing a hairy woodpecker at feeding stations that was “more a dirty white or tan” and “looks very similar to the Pacific variation pictured in Sibley.” “The Sibley Guide to Birds” depicts all the “field identifiable forms” or birds you can see, in this case including one of the subspecies of hairy woodpeckers from the western states. While I do love being on the lookout for the next rare vagrant to show up in Maine, there is a more plausible explanation to this off-color woodpecker.

Our typically black-and-white woodpeckers are looking dusky, or sometimes yellow, right now because of the trees they are nesting in. Woodpeckers are primary cavity nesters, meaning they excavate their own cavities in trees for nesting each year (which many other species, secondary cavity nesters, will use in subsequent years) and we are in the peak of their nesting season right now. The woods of Maine are filled with the incessant begging calls of woodpecker chicks calling from cavities right now, and each one will have a pair of adults making regular food deliveries. With each delivery, the adult will be going in and out of that hole they’ve created, rubbing against the rim of the cavity, which stains their feathers with the tannins from the tree.

This tannin-stained look does make our hairy woodpeckers look much more like the dark subspecies of the west, but there are some other ways to tell them apart, especially by looking at the wings. The pacific hairy woodpeckers comprise four subspecies referred to as “harrisi group.” Along with the browner body feathers (instead of white) they also show dark wing coverts. These small feathers on the wing, near the bird’s shoulder, are all black on the western birds, while the birds we have in the east have white spots on those coverts. Neither of these populations is considered migratory, so they stay resident in their respective ranges and are very unlikely to show up as vagrants outside of their expected areas.

As we head into August and the nesting season wraps up, hairy woodpeckers will have the time and energy to molt their feathers and a newly grown set will give them the contrasting black-and-white appearance we expect from them.

Do you have a nature question for Doug? Email questions to [email protected] and visit maineaudubon.org to learn more about birding, native plants, and programs and events focusing on Maine wildlife and habitat. Doug and other naturalists lead free bird walks on Thursday mornings, 7 to 9 a.m., at the Gilsland Farm Audubon Sanctuary in Falmouth.

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