An online resource based on the award-winning nature guide

Feathers

American Bitterns Displaying

5-3-14  American Bittern3  058American Bitterns are very secretive marsh-dwelling birds and have coloration so cryptic that you can be looking right at one and not see it, especially if it employs its “look like a reed” stance, with bill raised towards the sky. Like other members of the Heron family, American Bitterns possess plumes. These large, white shoulder feathers are visible only at this time of year, during territorial and courtship displays and just prior to copulation, when they are erected. Not only do these plumes impress female bitterns, but they make it much easier for humans to spot the displaying males.

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Ruffed Grouse Wings

2-25-14 grouse wing imprints  010You can often determine the type of flight that a bird is capable of by looking at the shape of its wings. Long, narrow wings are excellent for gliding, while the short, rounded wings of a Ruffed Grouse allow for tight maneuvering in the dense forests where they live. The shape of their wings and their quick-contracting muscles equip grouse for the short bursts of high speed (not long distances) they take when feeding or evading predators. (Photo: a Ruffed Grouse walked a short way and then took flight, beating its wings against the snow twice before it was airborne.)

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Big Birds

blue jay puffed out in snow 101Is your bird feeder being visited by gigantic Blue Jays and Black-capped Chickadees during this cold spell? Your eyes aren’t fooling you; birds often appear larger in very cold weather.
Birds that remain in New England year round must not only be able to find enough food in the winter to produce heat and energy, they must find a way to retain the heat. Various strategies have evolved, but feather structure and function play an important role for the winter survival of all birds. There are different types of feathers, each designed for a different function. A (wing or tail) feather consists of a central, hollow shaft on either side of which are many interlocking rows of barbs. The feathers that cover the body of a bird (contour feathers) often have interlocking barbs only at the ends, on the part not covered by an overlapping feather. The bottom-most, unconnected barbs on these feathers are similar to those of down feathers – loose and fluffy. When the temperature dips, birds often puff out their contour feathers (making the birds look huge). This action, and the structure of the bottom portion of the contour feathers,
increase the number and size of air pockets between the bird’s feathers and its skin. This space provides excellent insulation, preventing much of the bird’s body heat from escaping.

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Waterfowl Vulnerable When Molting

8-23-13 canada goose remains 043All North American birds replace their old, worn plumage with new feathers at least once a year, a process known as molting. Most birds have what is called a “sequential molt,” in which their flight feathers are lost one at a time (from each wing). This allows many birds to continue flying while molting. However, during their annual molt, waterfowl undergo a “simultaneous wing molt,” losing all of their primary wing feathers at once, preventing them from being able to fly for a month or more while their new primaries are growing in. During this period, they are extremely vulnerable, as this photograph testifies to. If you look closely at the remains of the Canada Goose’s wing on the right in the photograph (dark feathers), you’ll see that the new primaries have almost, but not quite, grown out of their sheaths, making them not yet functional. It’s apparent that this bird was unable to take flight during its molt in order to escape its predator.

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Common Grackle Threat Display

5-3-13 common grackle DA8A1629Although the common grackle, a member of the blackbird family, is the bane of many corn growers as well as a threat to songbirds trying to raise young (grackles eat other birds’ eggs and nestlings), it is quite a colorful bird, with its pale yellow eyes and iridescent purple plumage. Grackles have already begun nesting and defending their territory, as can be seen from the stance of the bird in this image. This “bill-up display” is a position assumed when a male is being approached on its territory by another male. It moves its head upwards so that its bill is almost vertical, signaling to the approaching grackle that it would be in its best interest to depart.


Red-winged Blackbird Epaulettes

3-11-13 redwing epaulettes IMG_2348Male red-winged blackbirds have returned to Vermont, and their most notable features are the brightly-colored reddish-orange feathers on their “shoulders”, referred to as epaulettes. In the military, an epaulette is a shoulder ornament that indicates, through its position, color, length and diameter, the bearer’s rank. Some birds, including male redwings, also possess this badge, or visual cue, which indicates the social status of the bird to other birds of the same species. Studies of male red-winged blackbirds and their epaulettes indicate (through dyeing their bright orange/red shoulder patches black) that epaulettes play a significant role in the male’s defense of his territory. Over 60% of the redwings that had their epaulettes dyed black lost their territories to other males. Further research revealed that aggression by a territorial male redwing is proportional to the epaulette size of the encroaching male redwing. It also indicated that male redwings intruding into redwing-occupied territories greatly limit the exposure of their epaulettes by covering them with black feathers. (Female red-winged blackbird plumage is brown and lacks epaulettes.)


Avian Heat Regulation in Winter

1-9-13 mallards on ice IMG_0203On a cold, winter day, why would any bird choose to sit down on ice? While feathers are excellent insulators, the legs and feet of most birds lack this protective covering. Because of this, legs and feet are a major source of heat loss for birds. Physical adaptations to this loss of heat include constricted blood vessels in a bird’s feet, as well as the proximity of arteries and veins to each other which aids the transfer of heat. Birds exhibit behavioral adaptations as well, such as ducks and gulls standing on one leg and tucking the other among breast feathers, reducing by half the amount of unfeathered limb surface area exposed. By sitting down and covering both legs, even on ice, heat loss from limbs is minimized. If you observe closely, you will see many of the ground-feeding finches such as sparrows and redpolls also occasionally drop down and cover their legs and feet with their breast feathers for a few seconds.


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