An online resource based on the award-winning nature guide

Birds

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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Wood Drilling Adaptations

2-4-15  hairy woodpecker 072Woodpeckers have begun their courtship drumming and they continue to excavate trees for food. Both of these activities involve a woodpecker’s head striking a tree’s surface at speeds up to 13 – 15 mph, and continuing to do so at over 100 strokes per minute. To sustain this kind of blow against a tree, woodpeckers have a number of skull adaptations, including strong yet lightweight skulls and bills, a network of bony supports within their skull, extra calcification of the portion of the skull nearest the tip of the bill, cushioning cartilage joining the bones between the skull and the beak, shock-absorbing neck muscles and a brain that is packed very tightly into the brain cavity.

A woodpecker’s brain, however, isn’t the only part of its anatomy that is adapted for drilling wood. A woodpecker’s nostrils are narrow slits (not circular, as in many birds) and are covered with bristly feathers that prevent wood chips and dust from entering them. Special cells on the end of its bill are constantly replacing material lost due to drilling. This keeps the chisel-pointed bill strong and resilient, while allowing it to be sharpened with every blow. And finally, less than a second before a woodpecker’s bill contacts wood, a thickened nictitating membrane closes over its eyes, protecting them from flying wood chips. (Photo: male hairy woodpecker)

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Common Redpolls Appearing

1-26-15 common redpoll male 077The birds most commonly associated with winter irruptions are the winter finches — Pine Grosbeak, Red Crossbill, White-winged Crossbill, Purple Finch, Pine Siskin, Common Redpoll, and Evening Grosbeak. Their food supply, or lack thereof, in the Canadian boreal forests where they normally overwinter, determines whether or not they will be seen as far south as the U. S. Key trees affecting finch movements in the boreal forest are spruces, birches and mountain-ashes.

Common Redpolls feed primarily on the catkins (seed-containing fruit) produced by birch and alder trees. When catkin production is low further north, as it is this winter, Common Redpolls leave these areas and irrupt into areas where food is more plentiful. (Photo: male Common Redpoll)

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Great Horned Owls Courting

1-22-15  great horned owl IMG_5973The intense hooting of Great Horned Owls begins in late December or early January, about a month before actual mating takes place. Males call during most seasons of the year, but the period when the males are hooting vigorously lasts for a month or six weeks. During the mating season the deep, rich tones of the males are occasionally interspersed with the higher and huskier notes of the females. The answering calls of the females are heard for only a week or two, toward the end of the six-week period.

Eventually, when a male and female approach each other, they do a sort of courtship “dance.” The male cocks his tail, swells his white bib (see photo), and with much bobbing and jerking utters a series of deep sonorous calls that elicit calling responses by the female. He cautiously approaches the female, continuing much tail-bobbing and posturing. The owls nod, bow, and spread their wings as well as shake their heads. Courting pairs have been observed engaging in high-pitched giggling, screaming, and bill-snapping. Mutual bill rubbing and preening also occurs. Copulation concludes the courtship ritual, with both owls hooting at a rate of 4 or 5 hoots per second throughout copulation, which lasts 4 – 7 seconds. (Photo: Great Horned Owl, in captivity)

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Lapland Longspur Plumage

1-20-15  lapland longspur IMG_6760The Lapland Longspur, named for the unusually long claw on its hind foot, breeds in the Arctic tundra and overwinters near fields throughout the northern half of the U.S. in flocks numbering up to four million birds.

Lapland Longspurs have two distinctly different plumages, especially the males. Their winter plumage (see photo) is streaked brown and somewhat dull. However, in the summer, the male’s plumage is very dramatic (see insert). The back of his neck, or nape, is bright rufous orange and black feathers form a distinctive facial mask and bib, bordered by a white stripe.

Unlike most birds with different breeding and non-breeding plumages, longspurs molt only once per year, in the fall, into their non-breeding plumage. How can the males look so different in the breeding season if there isn’t a second molt? By spring, the outer tips of these feathers have worn off to reveal the males’ (and females’, but to a lesser degree) distinctive breeding plumage underneath. (Insert photo from public domain)

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Owl Night Vision

1-5-15  barn owlIMG_6003Like humans, birds have a sensitive retina in the back of their eyes that absorbs incoming light, senses it, integrates the information in it, and sends this information on to their brain. An avian retina is much thicker than ours and contains more rod cells (for dim light vision) and cone cells (for acuity and color vision).

As most owls are active at night, their eyes must be very efficient at collecting and processing light. The eyes of owls are disproportionately large compared to the size of their skull, and enable them to collect as much light as possible. In addition, the retina of an owl’s eye has an abundance of light-sensitive rod cells — owls have almost a million rods per square millimeter compared to humans which have only about 200,000. Barn owls can see a mouse at 6 – 7 feet with an illumination of .00000073 foot-candles – the equivalent of humans seeing a mouse by the light of a match a mile away. Eye size, an abundance of rod cells and additional neural mechanisms provide owls with vision greater than that of most of their prey.

Since owls have extraordinary night vision, it is often thought that they are blind in strong light. This is not true, because their pupils have a wide range of adjustment, allowing the right amount of light to strike the retina. Some species of owls can actually see better than humans in bright light. (Photo: barn owl, in captivity)

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Overwintering Red-tailed Hawks

12-24-14 red-tailed hawk-juvenile 002Red-tailed hawks are “partial migrants” — some individuals are migratory, and others are not. Many Red-tails living in the northern portion of the species’ range in southern Canada and northern United States migrate to more southerly locations for the winter. A few northern birds, however, remain on their breeding territories even in the most severe winters.

Overwintering Red-tailed Hawks are generally easy to spot, as they often perch on dead trees overlooking open fields and on telephone poles next to highways, where they watch for prey. Mice, voles, squirrels, snowshoe hares and an occasional bird make up most of their diet. If you notice the coloration of a Red-tailed Hawk’s tail, it will tell you whether the bird is a juvenile or adult. Adults have rufous tails; juveniles have barred, brownish tails. Seconds after this photograph was taken this juvenile Red-tailed Hawk killed and consumed an American Crow while being mobbed by more than 50 other crows.

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