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Blue Feathers

The colors in the feathers of a bird are formed in two different ways, from either pigments or from light refraction caused by the structure of the feather. Red and yellow feathers get their color from actual pigments (carotenoids) that come from the bird’s diet. Blue, however, is a structural color, created by the way light waves interact with the feathers and their arrangement of protein molecules, called keratin.

Thus, no birds have blue feathers made from pigments – they are blue strictly from the structure of the feathers.  Different keratin structures reflect light in subtly different ways to produce different shades of what our eyes perceive as the color blue.

If you observe the blue feather of an Eastern Bluebird, Blue Jay or Indigo Bunting in normal lighting conditions you will see the expected blue color. However, if the feather is back-lit, and the light is transmitted through the feather, it will look brown. The blues are lost because the light is no longer being reflected back and the brown shows up because of the melanin in the feathers.

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Black-crowned Night Herons: Not Your Typical Heron

When you think of a heron, you usually think of a diurnal wading bird that has long legs, a long neck and a long bill.  Black-crowned Night Herons don’t possess any of these familial characteristics.  Stocky and relatively short-legged and short-billed, these herons typically rest during the day and start actively hunting at dusk, continuing through the night.

Prey includes fish (half their diet) plus a wide range of other creatures including leeches, earthworms, insects, crayfish, snakes, turtles, small mammals, birds and frogs. The manner in which a Black-crowned Night Heron lures and captures its prey varies.  Two of its most intriguing fishing techniques include bill vibrating (opening and closing its bill rapidly in the water to attract prey) and bait fishing – using bait to attract fish.

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Northern Mockingbirds Wing-flashing

Occasionally one comes across animal behavior that has yet to be understood by humans.  If you watch Northern Mockingbirds for any length of time, especially females, you are likely to see them stop and raise their wings half to fully open, in several progressively higher jerky movements.  When they do this, their white wing patches are fully exposed. 

Ornithologists are not of one mind as to what this behavior achieves. Perhaps it is anti-predator behavior – an attempt to scare would-be nest raiders away.  It could be a way of startling insects enough to make them move and thus easier to see and catch.  It also could be a form of territorial display/defense. Interestingly, mockingbird species that lack the white wing patches also engage in this behavior.

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Turkey Vultures Staying Cool

On hot, humid summer days, consider the ingenuity of the Turkey Vulture.  When overly hot, this bird will often defecate on its own legs.  The water in its waste (feces and urine are eliminated simultaneously through a bird’s cloaca) evaporates and cools the blood vessels in the Turkey Vulture’s unfeathered legs and feet, which results in cooling the entire bird.

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Parental Feeding Techniques of the Great Blue Heron

Great Blue Herons are colonial nesters – a rookery can have hundreds (up to 500) of nests, usually in dead snags, with one, two or three nests in a single snag.  Because the chicks are in the nest for roughly two months before fledging, their interactions with both parents, especially when food is delivered to the nest, has been observed and well documented.

Newly hatched chicks peck at the adult’s bill, the nest and each other. Initially the adult returns to the nest  where it stands on the rim and regurgitates food into the open bills of the chicks.  The chicks get quite proficient at grabbing the adult’s bill and pulling it into the nest as soon as the parent returns.  As the chicks age, the adult often regurgitates onto the floor of the nest and the chicks eat it.  When the nestlings are about a month old, they take food directly from their parents.

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Common Grackles Raising Young

Although female Common Grackles do all the incubating, both males and females provide food for their nestlings.  Males average almost two feedings an hour, females almost four. Judging from the size of the larvae the pictured Grackle has in its beak, its nestlings are midway to fledging, perhaps a week old. The older/larger the nestlings, the greater the size of the food they receive.  Male and female nestlings received items of equal quality and quantity.

During the breeding season, both nestlings and adults feed primarily on insects in addition to a small amount of grain (and an occasional fish, small rodent or leech).  During the winter, their diet consists mostly of agricultural grains and tree seeds such as acorns.

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Brown-headed Cowbird: Brood Parasite

One has to admire a creature who has managed to eliminate the laboriousness of raising its offspring.  Brown-headed Cowbirds, renowned brood parasites, have done just that.  These birds do not build nests; females lay up to 40 eggs a summer in the nests of more than 220 species of birds which raise their young for them.  Cowbird eggs are generally larger than the host bird’s and hatch in fewer days, thereby putting Cowbird chicks at a distinct advantage over the host’s chicks when it comes to parental attention.

In this photo a Brown-headed Cowbird has deposited three eggs in the nest of an Eastern Phoebe (which has constructed its nest inside an abandoned American Robin nest). Unlike some songbirds, Phoebes do not recognize and remove the Cowbird’s eggs. Neither do they build a new nest on top of the old one, as some smaller songbirds (i.e. Yellow Warblers) are known to do.

Cowbird chicks develop faster than the chicks of the host bird, thereby often getting the first crack at the food parents bring to the nestlings.  Not only are the host species’ chicks often at a disadvantage when it comes to parental care, but they are at the mercy of the Cowbird chicks which often remove both the eggs and chicks of the host. (Thanks to friends in Thetford, VT for the use of their photograph of this parasitized Eastern Phoebe nest. The three larger, speckled eggs are Brown-headed Cowbird eggs; the four smaller white eggs are Eastern Phoebe eggs.)

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Purple Martins Face Challenges Upon Returning To Breeding Grounds

Many of the Purple Martins that return from South America to the Northeast to breed have flown across the Gulf of Mexico to get here.  Once they’ve made this impressive trip, their challenges are far from over.  The reproductive success of Purple Martins depends not only on their arriving on their breeding grounds, but on surviving once they have arrived. One of the largest challenges that faces them upon their return is related to their diet, which consists exclusively of flying insects.  Purple Martins are particularly susceptible to spells of cold and rainy weather during the spring and early summer which can drastically reduce their supply of food.

Even when the weather doesn’t present them with nutritional challenges, Purple Martins have to contend with European Starlings and House Sparrows, both of which aggressively compete with them for artificial/human-made nest sites. Human intervention and management is often needed in order to protect the martin population. (Photo: male Purple Martin)

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Mourning Dove Nesting Idiosyncracies

Nest-building and chick-feeding are a bit unusual for Mourning Doves.  As to nest construction, the female remains at the nest site while the male dove collects the nesting material (twigs, grasses, pine needles, etc.). He returns to the nest and proceeds to stand on his mate’s back while presenting the material to her and she weaves it into the nest.  

The hatchlings, or squabs, are fed by regurgitation.  For the first four or five days, the squabs insert their bills in each side of either parent’s mouth and drink what is referred to as crop milk, a secretion from the lining of the crops of the parents.  All pigeons and doves produce crop milk for their young.  Seeds are regurgitated in increasing amounts and by the time the squabs fledge, they are essentially seed eaters like their parents. (Note: With a little effort, scruffy feathers of squabs can be seen beneath the breast of this nesting Mourning Dove.)

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Wild Turkeys Feeding and Making Burdock Balls

Almost every response to this Mystery Photo was spot-on, but “myip2014” was the first NC reader to recognize the signs left by a Wild Turkey feeding on Common Burdock (Arctium minus) seeds. A variety of plant material is eaten by Wild Turkeys in the winter: white pine and hemlock needles and buds, evergreen ferns, lichens, moss, and buds and stems of Sugar Maple, American Beech and American Hophornbeam trees. Especially when there is deep snow, Common Burdock is a favorite due to having seeds that are within reach and usually above the snow.

Turkeys consume these seeds in such a distinctive manner that one can recognize what animal has been feeding on burdock, even if tracks and scat are not present. The burdock burrs, or fruits, are plucked off the plant by the turkey, opened and the seeds are eaten. The burrs end up nearly inside out as a result of the turkey prying them open to get the seeds, and often are stuck together and form “burdock balls.“  The presence of these balls is a sure sign that turkeys have dined on the seeds they once contained.

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American Tree Sparrows : Winter Visitors

One of New England’s common winter visitors from the far northern tundra is the American Tree Sparrow (Spizelloides arborea), often spotted in large flocks in weedy, snow-covered fields moving from one spot to another as they feed..  These seed-eating sparrows are known to beat weeds with their wings and then fly to the surface of the snow beneath the weeds to retrieve seeds they have caused to fall.  

Their common name is a misnomer, for American Tree Sparrows feed on the ground and often breed and nest on the ground above the treeline.  They apparently reminded European settlers of the Eurasian Tree Sparrow (Passer montanus), a cavity-nesting bird which has very different habits than the American Tree Sparrow. 

In part because of the loss of weedy old fields and other open habitats, the American Tree Sparrow population has declined by 53% over the last 50 years.  Even so, they are a common sight during the winter in fields, on road sides and at feeders throughout the northern half of the United States.

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White-winged Crossbills Foraging

Most of New England is privileged to see White-winged Crossbills (Loxia leucoptera) only during the winter, when these nomadic birds forage south of their far northern boreal forest breeding grounds for conifer seeds during poor cone crop years. 

Spruce seeds are the preferred food of White-winged Crossbills. Their crossed mandibles allow them to pry open cone scales and they then extract the seeds with their tongue.  Individuals can eat up to 3,000 conifer seeds a day!

These birds have been documented nesting every month of the year.  As long as they can find a source of food that is sufficient for egg formation and that is likely to remain for the next month or so when they’ll be feeding nestlings, they will breed.  The larger the spruce cone crop, the longer a span of time crossbills typically nest.  Nesting usually declines by November although young do occasionally fledge in December and January. (Photos of a male White-winged Crossbill by Erin Donahue.)

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Birds Gathering Grit On Dirt Roads & Roadsides

Birds compensate for their lack of teeth with a two-parted stomach, the first of which (proventriculus) secretes digestive enzymes and the second of which (a muscular gizzard) grinds the food they’ve eaten into small digestible bits.  Birds that eat hard seeds and nuts tend to have thick, muscular gizzards, while those species that eat very easily-digested foods such as soft-bodied insects, soft fruits, or nectar often have very small and thin-walled gizzards.  Many birds whose diet consists of hard substances, including seed-eaters, swallow grit (often why you see them on dirt roads or the sides of plowed roads where dirt has been exposed) to enhance the gizzard’s ability to pulverize food.

At this time of year, American Goldfinches, Common Redpolls, Snow Buntings, Tree Sparrows and Eastern Bluebirds (among others) can be found swallowing roadside grit to help grind up the seeds that they consume.  (Photo:  While a majority of their summer diet is insects, Eastern Bluebirds consume many fruits (containing hard seeds) during the winter, a change in diet that allows them to remain in northern New England throughout the year.)

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Snow Buntings Feeding

Congratulations to Kathie Fiveash, the first NC reader to correctly identify the tracks and feeding sign in the latest Mystery Photo as those of Snow Buntings (Plectrophenax nivalis).  These birds began arriving in the northern half of the United States from their summer home on the northern tundra last fall and will remain here until March, when they begin migrating back to their breeding grounds.

In the winter, 97% of a Snow Bunting’s diet is weed seeds, including those of knotweed, ragweed, amaranth, aster, goldenrod, grasses and grains. These birds forage on the ground, collecting seeds from the protruding stems of tall weeds, occasionally reaching or leaping up to take seeds from taller stems, jumping against stems to scatter seeds or bending stems over by stepping on them. (Birds of the World, Cornell Laboratory of Ornithology)

While foraging, Snow Bunting flocks are constantly restless, frequently flushing rapidly and low over the ground for short distances.  A flurry of birds, much like snowflakes, fills the air nearest the ground for a few seconds while they relocate to a new area. Birds at the back of the flock fly forward to the front, creating the impression that the flock is rolling along.

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Fish are a primary, but not exclusive, food source for Bald Eagles

Hands down, Bald Eagles (like the 2nd year immature bird pictured) prefer fish over other prey — roughly 56% of the diet of nesting Bald Eagles consists of fish such as salmon, herring, shad, and catfish.  However, eagles are opportunistic foragers and over 400 species of prey have been recorded, half of which are waterbirds. Reptiles, amphibians, invertebrates such as crabs and crayfish, and small mammals such as squirrels, rabbits, muskrats, young beavers, fawns and raccoons are also subject to Bald Eagle predation.

During their first year, until they learn to be proficient hunters, Bald Eagles frequently feed on carrion. Even as adults, eagles regularly consume roadkills and deer that have died as a result of being stranded on ice. Whatever food is available and requires the least amount of energy to capture is usually high on their list.

Although not considered a primary source of food, domestic pets are subject to occasional predation by eagles. A discovery made by Fish & Wildlife personnel engaged in banding Bald Eagle nestlings may be of interest to cat owners who allow their pets to roam free in the great outdoors.  Upon reaching one nest, they found, among the detritus, over 20 cat collars.

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The Feathered Legs & Feet of Snowy Owls

Snowy Owls, inhabitants of the Arctic, are not only well camouflaged but well insulated with their feathers. Their exceptional density make Snowy Owls North America’s heaviest owl.  Weighing in at about four and a half pounds, they are about a pound heavier than Great Horned Owls and almost twice the weight of Great Gray Owls (North America’s tallest owl).

Most species of owls have densely-feathered legs (exceptions being owls living in southern regions such as Barn Owls, Burrowing Owls, and some tropical species).  Snowy Owls have exceptionally thick feathering on their legs and feet. The toe feathers of a Snowy Owl are the longest known of any owl, averaging 1.3 inches – in comparison, the Great Horned Owl’s (which has the second longest toe feathers) are a mere .5 inch. In addition to their insulative quality,  the feet and leg feathers may also serve to sense contact with prey and to protect against prey that might bite when seized.

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Owls & Eyelids

All birds have three eyelids – like humans, they have an upper and lower eyelid.  Owls are among the only birds that have a larger upper eyelid than lower eyelid. They are the only birds that blink like humans, by dropping their upper eyelids. But when owls sleep, they close their eyes the way other birds do—by raising the lower lids.

Beneath the two outer eyelids birds have a translucent nictitating membrane, sometimes called a “third eyelid.”  This membrane sweeps across the cornea from the inside corner of the eye to the outer edge of the eye. It moistens and cleans the cornea, especially in flight.  It is also drawn across the eye when there is a chance the eye might be scratched or damaged such as when capturing prey, flying through brush or feeding their young.

In summation, one could say that owls have three eyelids for each eye: one for blinking (upper), one for sleeping (lower), and one for keeping their eyes clean and protected (nictitating). (Photo: Snowy Owl sleeping, with lower eyelids raised.)

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Northern Cardinal Nests: Safety in Numbers

This is the time of year to keep an eye out for bird nests that were hidden by leaves all summer. Their location can reveal more than one might guess.  As with many bird species, the female Northern Cardinal does most of the nest-building herself, usually selecting a site that is in dense shrubbery, often in a tangle of vines.  Frequently there are two broods, but rarely is a nest reused.  Instead, a new nest is built for the second clutch of eggs, and it can intentionally be located quite close to the first nest.

The two pictured Cardinal nests were both built this year, only four feet apart in a grape vine-covered stand of Staghorn Sumac. Two different birds would not have nested so close to each other due to territoriality; thus, the same bird most likely built both nests. Ornithologists feel that the presence of old nests may function as protection against predation.  They found that when they placed an empty Cardinal nest adjacent to a Cardinal nest containing plastic eggs, there was significantly less predation than with single Cardinal nests. (Thanks to Jody Crosby for photo opportunity.)

(NB:  Even though most songbirds only use their nest once and then abandon it,  one needs a federal permit to collect bird nests.)

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White-crowned Sparrows Migrating

White-crowned Sparrows (Zonotrichia leucophrys) breed north of New England and overwinter south of New England.  The only time we get to admire their elegant plumage is during migration, primarily in May and October. 

White-crowned Sparrows are strong migrators (A migrating White-crowned Sparrow was once tracked moving 300 miles in a single night.) but they do have to stop and refuel along the way.  Because they are now passing through New England, you may see what at first might appear to be a White-throated Sparrow, but is a White-crowned Sparrow.  Their bold black-and-white striped crowns are one quick way to tell one species from another. (Immature birds have brown and gray stripes.)  Look for them foraging in weeds along the roadside or in overgrown fields.  About 93% of their diet is plant material, 74% of which is weed seeds.

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Yellow-bellied Sapsucker & European Hornet Sign

Congratulations to “mariagianferrari,” who came the closest to solving the Mystery Photo when she correctly guessed that the missing bark was the result of a partnership between an insect and a Yellow-bellied Sapsucker (Sphyrapicus varius).  The sapsucker arrived first and pecked the vertical rows of rectangular holes in the trunk of the tree in order to obtain sap as well as the insects that the sap attracts.  (Usually these holes are not harmful, but a tree may die if the holes are extensive enough to girdle the trunk or stem.)

The second visitor whose sign is apparent between the sapsucker holes is the European, or Giant, Hornet (Vespa crabro).  This large (3/4″ – 1 ½ “) member of the vespid family was introduced to the U.S. about 200 years ago. Overwintering queens begin new colonies in the spring and the 200-400 workers of a colony then forage for insects including crickets, grasshoppers, large flies and caterpillars to feed to the larvae. 

In addition, the workers collect cellulose from tree bark and decaying wood to expand their paper nest, which is what has occurred between the sapsucker holes, effectively girdling the apple tree.  The nutritious sap that this collecting exposes is also consumed by the hornets. We don’t often witness this activity because most of it occurs at night.

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Snowy Owls Starting Their Return To The Arctic

Every year in North America some Snowy Owls migrate southward during Arctic winters while some remain in the Arctic.  (In some winters — not this one — we see large numbers, or irruptions, of young owls in the Northeast which is thought to be a result of food and weather conditions further north.)  Individuals that spend the winter in New England usually can be found near large, open terrain that resembles their Arctic breeding grounds. Agricultural fields, coastal dunes and airports provide them with an ample diet of small mammals and birds.  Overwintering Snowy Owls begin to head northward in March and April. Occasionally a few owls linger on wintering grounds well into spring and summer (records of Snowy Owls exist in May in Massachusetts and June in New Hampshire).

Much has been learned about the migratory flights of Snowy Owls due to satellite tracking. According to Birds of North America, in February 2012, a transmitter attached to a female at Logan Airport in Boston, MA tracked an owl to Nunavut, Canada. The owl migrated north along Hudson Bay’s eastern shore during spring migration and returned south along Hudson Bay’s western shore during the autumn migration. It eventually returned to Logan Airport the following November, having completed a 7,000 mile round trip.

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Admirable Qualities of the Canada Jay

Most of New England never sees Canada Jays (formerly called Gray Jays), but in the northern reaches of the Northeast this bird is familiar to most boreal woods walkers.  It’s not hard to find something to admire about the cleverness of Canada Jays.  Admirable traits include their habit of using their sticky saliva to glue bits of food behind bark or in other vegetation during the summer (as well as the ability to be able to find it again when hungry in the winter), their use of forest tent caterpillar cocoons to hold their nest of twigs together, and their ability to incubate eggs in -20°F during their late winter nesting season.

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Bird Nests Revealed

Deciduous leaves have fallen, revealing bird nests that were right under our noses all summer without our even knowing it.  In addition to building in specific habitats and constructing different sized nests, each species of bird uses a combination of building material that is slightly different from every other species. Because of this, the material a bird uses to construct its nest can be diagnostic as far as determining what species built the nest.  Is the nest lined with rootlets? Are grape vines incorporated into the nest? Is moss covering the outside of the nest?  Is there a shed snake skin woven into the nest? The answer to these questions and others can help narrow down the list of possible builders.

This is the time of year to look for nests and try to determine, with the help of a good field guide such as Peterson’s Field Guide to Bird Nests, the identity of the birds that built them.  (Be aware that possession of a bird nest, egg or feather of most migratory birds, even for scientific research or education, is illegal if you do not have a Federal Migratory Bird Scientific Collecting Permit.)

Sometimes you’ll find material in nests that surprise you — some contain man-made, as well as natural, materials. Among the most unusual examples of this are a nest built solely out of barbed wire by a Chihuahuan raven in Texas and the pictured clothes hanger nest built by a crow near Tokyo and photographed by Goetz Kluge.

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Spruce Grouse Foraging

While Ruffed Grouse are plentiful throughout most of New England, one has to go to northern Vermont, New Hampshire or Maine to see its cousin, the Spruce Grouse.  Associated with boreal forests, this largely herbivorous bird feeds primarily on the needles of pine, spruce and fir (a small amount of animal matter is consumed in the summer as well as ground vegetation). Especially in the winter, a large volume of conifer browse is consumed in order to meet energy demands.

The grouse holds the needle between the tips of its mandibles and breaks it off by flicking its head.  This action, and the fact that Spruce Grouse feed exclusively on needles in the winter, leads to the wearing off of the tip of the bird’s upper mandible by spring.

If you are searching for a Spruce Grouse, you might want to concentrate in the middle of the crowns of trees, as this is where the birds tend to forage. Theories for this preference include the fact that needles in this location have higher nutritive value, branches provide sturdy support, and grouse can see approaching avian predators while remaining partially concealed. (Birds of North America, Cornell Lab of Ornithology). (Photo: male Spruce Grouse browsing on Tamarack needles and (inset) looking for grit on the ground.)

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