Baffling Bird Behavior — Your Questions Answered

1. What spring bird persistently sings, day and night?

A: Your bird is most likely to be a northern mockingbird. Don’t worry, male mockingbirds only perform this nocturnal singing in the spring and summer during the time of the full moon. Try running an electric fan (to create a buffer of sound) and using your earplugs on those nights when the male mockingbird is singing. Having a mocker around is a good thing—you might even consider yourself lucky!

An excellent source for backyard bird identification is An Identification Guide to Backyard Birds.
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2. How long before robin eggs hatch, and when do the young leave the nest?

A: Robins incubate their eggs for 12 to 14 days. Once hatched, the nestlings remain in the nest for another 14 to 16 days before fledging.
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3. Do Carolina wrens normally leave their eggs unattended?

A: Yes, this is normal when the female is completing the clutch of eggs. Female songbirds typically lay one egg each morning for four to five days until the clutch is complete. Then they begin incubating the eggs. This way the eggs all develop at the same time and hatch synchronously. For more information on nesting birds, get a copy of A Guide to Bird Homes.
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4. Can you identify the birds flocking around our chimney at nighttime?

A: The birds are appropriately called chimney swifts, named for their preferred nesting location, inside chimneys. During fall migration small flocks of swifts gather into large communal roosts numbering hundreds or even thousands of individuals. Your chimney appears to be a migrating roost for chimney swifts. For more information, I suggest you check your local library for a good bird book. In most good bird books you’ll find a profile of the chimney swift that will explain the species’ natural history and behavior.
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5. Why do American crows groom/massage/stroke each other?

A: Ornithologists call this allo-preening and it occurs in a wide variety of birds including small finches, macaws, raptors, and crows. It is a ritualized form of behavior that apparently bridges the gap between aggressive attacks and sexual behavior.
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6. Why do large groups of blackbirds or American crows often attack a single hawk?

A: Mobbing behavior by crows is very common. The crows are reacting to the potential threat the hawk poses as a predator, to the adult crows and their offspring. The mobbing often serves to harass the hawk into leaving the area. Occasionally a mobbed hawk will turn the tables and attack and kill a crow.
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7. How can I stop a woodpecker from pecking holes in my stucco house?

A: A woodpecker drilling on your wooden house is only doing what comes naturally to it: drilling into wood in search of shelter or food. The birds frequently mistake the buzzing of electrical wires and appliances for a colony of wood-boring insects or ants—a major part of a pileated woodpecker’s diet. House siding also offers woodpeckers a sheltered cavity ideal for initiating courtship behavior or territorial defense (flickers are notorious for drumming on drainpipes and chimney flues at dawn).

Woodpeckers also use wood and sometimes metal parts of houses as drumming sites. They drill their bills against the surface in a rapid staccato beat. This drumming noise is a territorial announcement, and a method of attracting a mate. Drumming happens most regularly in the spring. There are several things you can try. One of them may work.

Placing wire, foil, sheet metal, or fencing over pitted siding may discourage pileated woodpeckers from pecking holes. Some homeowners have successfully deterred them using owl decoys, rubber snakes, loud noises, motion detectors, or by simply spraying the birds with a hose. In extreme cases, wildlife officials will “remove” a problem bird at the homeowner’s request.

Most house-wrecking woodpeckers do their damage in the fall, which is when they begin making their winter roost holes. Try mounting a nest box with an approximately same-sized hole over the drilled area. Fill the house with wood chips, and you may divert the bird’s attention and gain a tenant.

For more information on woodpeckers, get a copy of Enjoying Woodpeckers More.
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8. Do large groups of robins indicate that a flock is migrating South for the winter?

A: American robins are surprisingly hardy as long as they have access to their winter food source: fruit, especially berries. They switch over in winter from their mostly insect-based summer diet. As such, robins are facultative migrants. This means that they will migrate only as far south as they need to or are forced to by bad weather or food shortages. During ice storms, when forest fruit are covered in a thick coating of ice, many robins flock together and move south. In the same way, if a robin spends the winter in your region, it’s probably because there’s enough fruit still hanging on to trees and branches to see it through.

The idea that robins are the true first sign of spring is somewhat mythical. In much of northern North America, a few robins overwinter, but they stick to the woods and thickets where they can find freeze-dried fruit. Most backyard bird watchers do notice the robins’ return when these birds appear on lawns with the onset of warm weather, seeking their warm-weather food: earthworms, grubs, caterpillars, and other insects.
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9. Do wrens eject young bluebirds from their houses?

A: The wrens you are seeing at your feeders are probably Carolina wrens. They can co-exist with bluebirds peacefully. The wrens compete with bluebirds for nest boxes are house wrens, which migrate south for the winter and will return in April and May to set up territories. Place your bluebird houses in the middle of a large grassy area, such as a meadow or large lawn. Place your wren houses along the edge of the trees or woods. This will keep the house wrens and bluebirds from fighting over housing.
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10.Do all birds mate for life?

A: No. Some species have unusually strong pair bonds between mated birds. These species include some eagles, cranes, swans, geese, and ravens. Being mated “for life” means, really, for as long as both birds are alive. When one of the pair dies, the other will take a new mate. Most North American bird species pair up primarily to reproduce, and go their separate ways soon after they have nested. In some species, such as the ruby-throated hummingbird, the pair bond is very brief. In the case of the rubythroats, the pair bond lasts only as long as courtship and copulation. The male has nothing to do with the incubation or raising of the young birds. For answers to the most commonly asked bird questions, get a copy of The Backyard Bird Watcher’s Answer Guide.
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11. Do all birds migrate?

A: Not all bird species migrate, but most do. Migration is defined as the seasonal movement of birds, north in the spring from the wintering grounds, and southward in the fall from the breeding grounds. Among the birds that are resident, or do not migrate, are many grouse, ptarmigan, and quail species, many owl species, some (but not all) woodpeckers, white-breasted nuthatch, Carolina wren, northern cardinal, wrentit, ring-necked pheasant, Townsend’s solitaire, common raven, gray jay, and northern mockingbird, and many others.
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12. A wren in my backyard is killing bluebird and tree swallow nestlings. What can I do to help protect these birds?

A: I recommend two strategies. First, move the tree swallow and bluebird boxes into an open clearing (near the center of your yard, for example). Next, place the wrens’ favorite shelter in edge habitat. A wren rarely ventures into open spaces to challenge other birds for housing, especially if adequate shelter is readily available in its preferred habitat.
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13. Why does the ovenbird sing in sudden bursts after nightfall?

A: During spring and early summer, male ovenbirds frequently sing at night, sometimes while flying over the woodland canopy. This courtship/territorial behavior is common during the breeding season, when the male becomes hormone-driven.
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