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Cavity Nesting Birds

Common Goldeneye Ducklings Fledging

Common Goldeneyes, also called “Whistlers” because of the noise their wings make in flight, are a boreal-nesting species of duck.  The eyes for which Common Goldeneyes are named have’t always been gold! They are gray-brown at hatching and turn purple-blue, then blue, then green-blue as they age. By five months of age they have become clear pale green-yellow. Adult males have bright yellow eyes, and females pale yellow to white.

Like Wood Ducks, Buffleheads and Hooded Mergansers, Common Goldeneyes are cavity nesters.   When it’s time to fledge (24-36 hours after the young hatch), the female flies repeatedly to the nest hole, and eventually sits below the cavity calling to her precocial young. They jump from the nest in rapid succession, joining her in the water if the tree is on the shoreline, or on land (they nest up to 8/10ths of a mile from water) if not.

The young swim and feed with ease immediately, and are diving within one to two days of leaving the nest. The female protects them and broods them at night and during bad weather for the first few weeks.  Even so, up to 56% of the young perish during their first week of life due to weather and predation.  (Thanks to Jody Crosby for photo op.)

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Hooded Merganser Ducklings On The Water

It’s hard to picture a duck flying straight into a cavity in a tree, but there are several species of waterfowl that do just that in order to incubate their eggs in a relatively safe location.  The female Hooded Merganser selects a nesting site in a living or dead tree cavity or in a handmade nest box. Once mating and egg-laying has occurred, the male disappears, leaving his mate to raise and care for their offspring.

Within 24 hours of her eggs hatching, the female calls to her young from the cavity opening or from the water below, encouraging them to leap up to the opening and hurl themselves out into the world. The entire brood departs the nest within a couple of minutes. As soon as they hit the water, the precocial young ducks are swimming, diving and feeding on water boatmen, backswimmers, diving beetles and other aquatic invertebrates.

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American Kestrel Chicks Fledging

 

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The American Kestrel is the smallest, most numerous, and most widespread North American falcon. Roughly two months ago these birds (formerly known as Sparrow Hawks) were mating and laying eggs in nesting cavities (natural tree cavities, woodpecker holes, nest boxes), most of which are located near open fields with low growth (to facilitate finding insects to eat).  The female kestrel does most of the incubating of her four to five eggs (one month), and all of the brooding (one month).  The male rises to the occasion and feeds the newly-hatched chicks for the first 7-10 days, and then the pair shares the feeding.

After 26 – 28 days in the nest, American Kestrel chicks are ready to fledge.  Their first flight, consisting of alternate fluttering and gliding, can be quite short or as long as 200 yards, and typically ends with an awkward landing.  After the chicks have fledged, the parents continue to feed them for up to 12 days. During this period young American Kestrels have been observed returning to their nest cavity to roost.

(Photo:  Male American Kestrel nestling, roughly 22 days old. Note feathered “eye” spots on back of head (serve to ward off predators) are already showing. Thanks to Joan Waltermire, John Douglas, David Merker, and Sebastion and Carter Lousada for photo op.)

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Downy Woodpeckers Nest-building

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Downy Woodpeckers are beginning to scout for potential nest sites, preferring the dead stubs of a living or dead tree. Both sexes have been observed selecting the nest site, although females do so more commonly. Just because you see a Downy Woodpecker pecking at a site, however, doesn’t mean it will end up nesting there, as excavation is often started at several sites before one is chosen.

When a potential nest site is decided upon by either sex, it often drums to inform its mate, and its mate often flies to the site and taps or drums in response. It takes about 16 days for both male and female to excavate a cavity. A round entrance hole of roughly 1 ¼” in diameter can make it hard for an egg-bearing female to squeeze into the nest. Egg-laying begins anywhere from one to ten days after the completion of the nest cavity, and three to eight eggs are laid, one per day, usually before 10 a.m.. (Photo: male Downy Woodpecker excavating nesting hole)

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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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