Cavity-nesting Birds Wasting No Time
There are roughly 85 species of North American birds that are cavity nesters – birds that excavate nesting holes, use cavities resulting from decay (natural cavities), or use holes created by other species in dead or deteriorating trees. Many of them get a jump start on open-nesting birds, due to added protection from the elements. Barred owls, titmice, chickadees, wood ducks, woodpeckers, bluebirds, mergansers – many have chosen a nest site and are busy excavating, lining a cavity or laying eggs long before many other species have even returned to their breeding grounds.
The reduced risk of predation a cavity nest experiences is reflected in several ways: many cavity-nesters have larger clutches of eggs than open-nesting birds and cavity-nesting young also spend a relatively longer period of time in the nest before fledging. When in the woods, keep an eye out for snags (standing dead trees) and stumps, for they provide housing for many cavity-nesting birds. (Photo: Black-capped Chickadee removing wood chips from the cavity it’s excavating in a rotting stump.)
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Early Nesting Hooded Mergansers Seeking Tree Cavities
In northern New England you are most likely to see Hooded Mergansers in the spring and fall when they are migrating to and from their breeding grounds in northern Canada (some nest in New England, as well). Hooded Mergansers tend to arrive in their breeding areas as soon as the ice starts to melt, and have been known to start laying eggs in March in Massachusetts and April in Vermont. Often some of the earliest eggs laid in a nest will freeze and crack and never hatch.
Hooded Mergansers are cavity nesters, frequently choosing trees that are close to ponds, marshes, swamps or streams. They compete with Wood Ducks for nest boxes put out by humans, and females of both species may lay eggs in the same nest, with one or the other incubating the eggs. Sometimes the duck that initiated the nest does the incubation, but more often the hen laying the majority of the eggs will do so. Because both species have the same incubation period, all the eggs hatch at the same time.
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Hooded Mergansers Fledglings are Dispersing
Within 24 hours of hatching, Hooded Merganser ducklings leap anywhere from 8 -90 feet from their arboreal cavity nest down to their mother, who is calling to them from the water below. Capable of swimming and diving right away, the ducklings begin feeding themselves immediately. Weighing little more than an ounce, they mostly eat insects, including backswimmers, water boatmen and diving beetles. Eventually, as the ducklings grow, they work their way up to fish and crustaceans — particularly crayfish, such as the pictured merganser has caught. In addition to its size, the lack of a real “hood” indicates that this Hooded Merganser is a youngster.
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