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Cavity Nesting Birds

Cavity-nesting Birds Wasting No Time

4-21-17 black-capped chickadee nest building IMG_4765There 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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Wood Ducks Returning

4-7-17 wood ducks 288Among the first groups of birds to move north in the spring are waterfowl. Many ducks, geese, and swans begin migrating as soon as frozen lakes and marshes start to thaw. Although an occasional Wood Duck is spotted in northern New England during the colder months, most winter further south (band recoveries indicate that in eastern U.S. about one-third of Wood Ducks are permanent residents and the others are migratory). They begin to be seen in open water in February and March but it is April before their numbers really swell, and sometimes it seems that on every stream and in every flooded field you can find at least one pair. With their distinctive plumage, it’s hard to miss them, especially the males. Soon they will be seeking out natural cavities in trees, including Pileated Woodpecker holes, in which to nest.

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Hooded Merganser Ducklings on the Water

6-17 hooded mergansers IMG_4318Hooded Merganser ducklings typically leap from their cavity nests in trees within twenty-four hours of hatching. Long claws on their feet aid them in climbing up to the opening of the cavity in order to join their mother who is calling from below. The ducklings feed themselves (aquatic insects and invertebrates) from day one, and are capable of shallow dives as soon as they leave their nest. The mother (who has been their sole caretaker since she started incubating the eggs) often moves her brood downstream to larger lakes, rivers and bays from smaller streams and ponds near the nest site. Eventually she leaves her young, anywhere from a month or two after they hatch, often before they can fly.

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Barred Owl Chicks View The World For The First Time

6-4-15  barred owl chicks2  100 Barred Owl eggs (usually two or three) are often laid in a tree cavity, where the adult female incubates them for roughly a month. Fuzzy, white, downy chicks hatch and remain inside the tree for four or five weeks while being fed by both parents. When the young owls are two or three weeks old, their white down is replaced with gray-buff secondary down, and they gain the strength to climb up the inside of the tree and peer out at the outside world. In and out they go, perching on the rim of the nest hole for half an hour or so as they await the arrival of their next meal, and then retreating back to the safety and warmth of their nest. (Thanks to Alfred Balch, naturalist extraordinaire, for photo op.)

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Early Nesting Hooded Mergansers Seeking Tree Cavities

4-6-15  hooded merganser, male 367In 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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Black-capped Chickadees Still Nest-building

7-5-13  black-capped chickadee 006Black-capped Chickadees tend to be early nesters, often as early as April, as they build their nest inside a cavity where it is sheltered from the cold. Chickadees rarely re-use a nest, so one might guess that this Black-capped Chickadee with nesting material in its beak in early July has a second brood on its way. However, it is unusual for Black-capped Chickadees to have a second brood of young after the first has fledged. If they lose the first brood, they sometimes will re-nest, but it’s more likely that this chickadee is just a late nester, as nest-building can and does occur up until mid-July. Both members of a pair excavate a cavity in a rotting tree, stump or post and then the female alone builds the nest inside the cavity. The foundation of the nest is usually made of coarse material such as moss. The lining consists of softer, finer material such as deer hair, rabbit fur, or in this case, an aging chocolate Labrador Retriever’s hair.


Beaver Ponds & Waterfowl

6-5-13 mallard & ducklings 151The relationship between beavers and waterfowl is a strong one. In creating ponds and wetlands, beavers provide valuable waterfowl habitat. Beaver ponds are attractive to most dabbling duck species, particularly American Black Ducks and Mallards (pictured). Dead snags that are often found in beaver ponds provide Hooded Mergansers, Common Goldeneyes, Buffleheads and Wood Ducks with nesting cavities. During spring and fall, beaver ponds are used by migrating waterfowl, such as Green-winged Teal and Ring-necked Ducks, for the fuel they provide (aquatic invertebrates, plant seeds, tubers, buds and rhizomes). Waterfowl surveys in 2002 in Wyoming found that rivers and ponds with beavers had 75 times more ducks than those without beavers.