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Feathers

Winter Adaptations of the Ruffed Grouse

Ruffed Grouse have both behavioral (diving into the snow on cold nights) and physical strategies for dealing with the cold, snow and ice of New England winters.  Three of the physical changes that take place in the fall are evident by looking closely at a grouse’s legs, feet and beak. The feathers on its legs grow thicker and further down towards its feet, to provide better insulation.  Small comb-like growths of skin, called pectinations, develop along either side of each toe.  These increase the surface area of a grouse’s foot, and serve as snowshoes in deep snow.  They also help the grouse cling to icy branches while it quickly snips off poplar and other buds at either end of the day.  And on its beak, feathers expand downward to cover its nostrils, slowing the cold air and giving it a chance to warm up before it is inhaled by the grouse.

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Birds Molting Old Feathers And Growing In New Ones

With birds, molting refers to the loss of old, worn feathers and the growth of new ones.  A molt can involve all of the bird’s feathers (complete molt), or just some of them (such as wing or tail feathers – a partial molt). Most birds have a complete molt once a year (chickadees, hummingbirds, owls, etc.), or one complete molt and a partial molt before the breeding season (buntings, tanagers, warblers, etc.), or two complete molts per year (Bobolinks, Marsh Wrens).

Complete molts often occur in late summer and early fall, after the breeding season is over. When you think about it, the timing of this “prebasic” or “postnuptial” molt makes a great deal of sense. Growing new feathers takes an inordinate amount of energy; food is plentiful now, the demands of breeding are over and for many birds, migration isn’t quite under way. It is the perfect time to look for molted feathers on the ground.  (Photo:  molted Red-tailed Hawk tail feather)

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The Feathered Feet of Northern Owls

3-14-17 great gray owl2 164

Most owls have feathered legs, but the feet and toes of some owls, especially those living in colder, higher latitudes, are also densely feathered. The feathers keep the feet of these birds warm, allowing them to hunt where snow is on the ground and temperatures are very low. Great Gray Owls (pictured), Snowy Owls and Northern Hawk Owls are all examples of this phenomenon. Owls living in warmer climes, such as Barn Owls, have sparsely feathered feet and toes, and tropical owls have nearly featherless feet. This variation can also be found within a given species that has a range that extends over many degrees of latitude, such as the Barred Owl.

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Bird Tail Feathers

mystery-photo-img_0672Although the number of tail feathers is quite variable across groups of birds, the most common number is 12. The left and right tail feathers are mirror images of each other. The outermost tail feather is highly asymmetrical (narrow outer vane, broad inner vane). The feathers become more symmetrical toward the center, with the two central tail feathers usually exactly symmetrical (vanes on both sides of the shaft equal in width). There is a similar change in the curvature of the tail feather shafts from outer to central, with the shafts of the outermost tail feathers usually strongly curved, gradually straightening toward the center, with the central tail feathers shafts completely straight.

Groups of birds can have certain tail feather traits in common. For instance, the tail feathers of most waterfowl are short (although the pictured female Hooded Merganser’s are relatively long), while many gamebird tail feathers are used in display and thus are boldly patterned and/or elongated. Woodpecker tail feathers have pointed, stiff tips that the birds use to brace themselves against tree trunks. Even within a group, such as waterfowl, there can be specific tail traits such as the drake Northern Pintail’s long twin tail feathers and the drake Wood Duck’s squared-off tail feathers.

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Canada Goose Goslings: Contour Feathers Replacing Down

Canada goose gosling 207Within 24 hours of hatching, downy Canada Goose goslings leave their nest and are capable of walking, swimming, diving and feeding themselves. Like many species of waterfowl, their growth is rapid. Contour feathers on their wings and tail begin to emerge in about three weeks (note wing feathers of gosling in photo). Feathers on a gosling’s head, neck and back are the last to appear. Just before a gosling develops the ability to fly, the last fluff of down, which is on top of its head, disappears.

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Male American Goldfinch’s Seasonal Plumage

3-17-15  male American goldfinch IMG_0482Most songbirds have one complete molt every year, in the late summer. Some, like the American goldfinch, have another (partial) molt in the spring. Last fall male goldfinches molted, replacing many of their bright yellow feathers with drab, greenish-gray feathers, so that they closely resemble females during the winter. Goldfinches start their partial molt in February, and in the next month or two, males will once again become bright yellow beacons. No-one can illustrate the subtle seasonal plumage changes of a male American goldfinch better than David Sibley: http://www.sibleyguides.com/2012/05/the-annual-plumage-cycle-of-a-male-american-goldfinch/ (Photo: male American goldfinch in March)

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Horned Larks Seeking Seeds

2-25-15 horned lark 025Horned Larks are named for the dark feathers near the back of their head that sometimes become erect and resemble horns. During the winter, these birds typically form large flocks which often include Lapland Longspurs and Snow Buntings. Horned Larks are usually found in fields where the snow has blown the ground bare, but they can also be found hunting and pecking on manure and silage piles. As they walk or run along the ground foraging for seeds on bare ground, these brown-backed birds are very well camouflaged (not so much on snow). There is a wide variation of shades of brown back feathers throughout their range, and researchers have found that their color is strongly correlated with the color of the local soil.

Horned Larks nest on prairies, deserts and agricultural land throughout much of the U.S., as well as the Arctic tundra. In another month, most of the Horned Larks overwintering in northern New England will migrate north.

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Ruffed Grouse Nostril Feathers

12-16-14 ruffed grouse nostrils IMG_2376Ruffed Grouse have adapted to cold winter months in a number of ways, from growing “snowshoe” pectinations on their toes to having their legs covered with fine feathers. Equally effective are the feathers covering a grouse’s nostrils, which are thought to heat cold air as the bird breathes in. (Thanks to Sara and Warren Demont for photo op.)


European Starling

European starling IMG_8398There was no fooling the vast majority of Naturally Curious readers! As unpopular as the European Starling may be, its plumage is impressive, especially at this time of year. The starling’s summer, or breeding, plumage shows purple and greenish iridescence, especially on the head, back, and breast. Following the annual mid-summer/fall molt, most head and body feathers have whitish or buff terminal spots. Through the winter, most of these light spots gradually wear away to produce a glossy black appearance in the spring.

Most creative Mystery Photo response (from Steve Adams): “ This one’s easy. The bird is Hazel Hainsworth. She was sweet but insane. Hazel had a huge hat made of all different kinds of feathers, and because she liked her scotch, her navigation skills were somewhat dull, and she always made a point of telling people she’d been lost in every state in the nation, including Alaska.”

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Ruffed Grouse Preening

ruffed grouse preening IMG_3515Birds have up to 25,000 feathers, and most birds preen, or clean, waterproof and align their feathers, several times a day. Ruffed grouse, as well as most other birds, possess an uropygial gland, or preen gland, on their rump. (Some types of birds, including owls, pigeons, parrots and hawks, lack an uropygial gland and instead have specialized feathers that disintegrate into powder down, which serves the same purpose as preen oil.) The preen gland produces a waxy substance that helps waterproof feathers and keeps them flexible.

Ruffed grouse reach back and rub their beaks on this gland, and then distribute the wax on their body and wing feathers by stroking them toward the tip. The grouse grasps a feather near the base and draws it through the partly close beak, nibbling as it goes. This distributes the wax and cleans parasites from the feathers. In order to preen its head, the grouse must rub it on other parts of its body. Preening is usually done in a fairly open setting but with a degree of overhead protection, so that the grouse can watch for terrestrial predators, while being protected from hawks and owls.

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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.


A Great Christmas Present!

If you’re looking for a present for someone that will be used year round, year after year, Naturally Curious may just fit the bill.  A relative, a friend, your child’s school teacher – it’s the gift that keeps on giving to both young and old!

One reader wrote, “This is a unique book as far as I know. I have several naturalists’ books covering Vermont and the Northeast, and have seen nothing of this breadth, covered to this depth. So much interesting information about birds, amphibians, mammals, insects, plants. This would be useful to those in the mid-Atlantic, New York, and even wider geographic regions. The author gives a month-by-month look at what’s going on in the natural world, and so much of the information would simply be moved forward or back a month in other regions, but would still be relevant because of the wide overlap of species. Very readable. Couldn’t put it down. I consider myself pretty knowledgeable about the natural world, but there was much that was new to me in this book. I would have loved to have this to use as a text when I was teaching. Suitable for a wide range of ages.”

In a recent email to me a parent wrote, “Naturally Curious is our five year old’s unqualified f-a-v-o-r-I-t-e  book. He spends hours regularly returning to it to study it’s vivid pictures and have us read to him about all the different creatures. It is a ‘must have’ for any family with children living in New England…or for anyone that simply shares a love of the outdoors.”

I am a firm believer in fostering a love of nature in young children – the younger the better — but I admit that when I wrote Naturally Curious, I was writing it with adults in mind. It delights me no end to know that children don’t even need a grown-up middleman to enjoy it!


Juvenile Cedar Waxwings Migrating

Possibly because of the importance of summer fruits in their diet, Cedar Waxwings (Bombycilla cedrorum) are late nesters, but by late August adults have begun their migration to the southern states and Central America.  This year’s young are beginning this (roughly) 900-mile flight now, a month after their parents have left. You can often find waxwings feeding in crab apple and other fruit trees where they stop over during their flight to refuel.  Juvenile birds lack the sleek look of adults — the red wax-like feather tips for which this bird is named have not developed, and the color of their plumage is much duller than that of the adults.


Juvenile Green Heron

Green herons are typically solitary and secretive birds, but if you find one, you often have an extended period of time to observe it, as they often slowly stalk their prey, or pose statue-like, sometimes for minutes at a time, while waiting to strike at a fish, frog or invertebrate. Three characteristics tell you that the green heron in the photograph is a juvenile: the tufts of down that remain on its head, its streaked neck (adults have solid rufous necks) and its yellow legs (adults have orange legs).


Red-tailed Hawk Nestling

The Red-tailed Hawk nest that produced two fledglings last year is in use again this spring.  In the past month the nestlings have gone from tiny white powder puffs to nearly equaling their parents in size.  Down is still visible, especially on their heads, but contour feathers are quickly replacing them on other parts of their body. Soon there will be wing stretches and flapping, as well as hopping about on nearby branches in preparation for fledging. 

 


American Bittern

American Bitterns have returned to New England from their southern wintering grounds, and are announcing their presence with a unique song that Sibley describes as a “deep, gulping, pounding BLOONK-Adoonk” that they repeat over and over.  These secret, well-camouflaged marsh birds are almost invisible as they slowly walk through marsh grasses.  When they stand still and point their bill skyward, they are easily mistaken for the reeds they inhabit.

 


Snow Buntings

Snow Buntings begin arriving in the northern half of the United States from their summer home on the northern tundra by the end of October, and remain here until March, when they begin migrating back to their breeding grounds. Although both males’ and females’ backs and heads are brownish, their bellies and a good portion of their wings are white, and when they take to the air, a flock of snow buntings bears a strong resemblance to a massive snow storm. By the time their breeding season arrives, the male has a totally white head and belly, and a jet black back.  This is not because of a second molt – snow buntings only molt their feathers once a year in the late summer – the change in appearance is due to the fact that underneath the colored feather tips, the back feathers are pure black and the body feathers all are white. The male wears off all of the feather tips by actively rubbing them on snow, which produces his black and white breeding plumage. (There is one male snow bunting in this photograph that is close to having breeding plumage — can you find it?)

 


Cedar Waxwing Feather

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Several of the secondary flight feathers (inner wing feathers) of Cedar Waxwings and Bohemian Waxwings possess tiny, brilliant red tips. (As Dale Martin pointed out, there is a bit of white next to the red tips of Bohemian Waxwings’ feathers, but those who guessed either waxwing should take a bow.) These “waxy droplets” give the bird its common name, along with its love of red cedar berries.  These drops of “wax” are actually the widened, flattened ends of the feather shafts.  The color is derived from a carotenoid pigment, astaxanthin, which they get from their diet (cedar fruit and other berries).  Younger birds possess fewer red tips than older birds. Ornithologist Peter Stettenheim conjectures that since the waxwing’s ability to find berries probably improves with age, the number, size and coloration of these tips may indicate the birds’ foraging ability.  Research in the 1980’s indicates that these red tips serve as markers in mating, providing visual clues to potential mates about each other’s age, which correlateswith egg size, clutch size, as well as ability to find and deliver food.  Cedar Waxwings tend to mate with individuals of their own age.