An online resource based on the award-winning nature guide

Birds

Owls & Humans Share Trait

barred owl 194Birds have three eyelids – an upper eyelid, lower eyelid and a third semitransparent membrane called a nictitating membrane that sweeps across the eye much like a windshield wiper. This membrane keeps their eyes moist, and protects their corneas from being scratched.

In most birds, including owls, the upper and lower eyelids are used to close the eyes when sleeping, and the nictitating membrane is used for blinking. Humans close their eyes mainly by lowering the upper eyelid, where most birds do so by raising the lower lid. Owls (and a few other birds such as parrots, toucans, wrens and ostriches) are more human-like in that their upper lids are usually lowered to close their eyes. Owls also usually close their eyes, partly or entirely, when capturing and transferring prey, scratching their face, preening another owl and copulating. (Note the rows of feathers on this barred owl’s upper eyelids.)

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Mourning Doves Calling

3-19-15 -mourning dove IMG_2091The mournful lament of the male mourning dove is often one of the first songs heard in the early spring. The frequency of this call builds to a peak from mid-May to mid-June. As in many other pigeons and doves, the Mourning Dove’s main call, or “perch coo” (coo-oo, OO, OO, OO) is an advertising call, sung in order to attract a mate. Unmated males often establish perches within their territory from which they repeatedly sing.

A shorter nest call is used by a paired male to attract his mate to a potential nest site. The male then gathers nesting material and presents it to the female while standing on her back. While she constructs the nest, he continues to use the nest call to maintain a bond with his mate. Once the nest is built, this call diminishes. You can hear Mourning Dove calls at http://www.allaboutbirds.org/guide/mourning_dove/sounds, although to my ear, it’s hard to distinguish the perch call from the nest call in these recordings.

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Patient (and Hungry) Barred Owls Visit Feeders

3-12-15 barred owl 152Barred owls are nothing if not resourceful when it comes to methods for finding food. Typically they sit on a high branch and scan the area for prey before dropping down to capture small mammals such as mice, squirrels as well as reptiles and amphibians. During summer months, they have been seen perched over water and swooping down to capture fish, as well as wading in shallow water to hunt for crayfish and fish. Barred owls have even been seen running along the ground and pouncing on amphibians.

Even with a myriad of hunting techniques, however, barred owls have had a hard time this winter, due to the depth of the snow (harder to hear and reach prey) and the time it is taking for it to melt. Small mammals, which compose the bulk of their diet, remain well hidden. Reports of barred owls perched patiently waiting and watching on or near bird feeders for unsuspecting rodents to expose themselves have become commonplace. Mice and voles that come out from under the snow to feed on spilled seed during the night are a life-saving source of food for these stressed birds. Warmer weather will hopefully soon improve hunting conditions for barred owls. Their gain will be our loss, for once again, as it should be, a sighting will become a far more rare occurrence. (Thanks to Emily and Joe Silver for photo op.)

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Returning Red-winged Blackbirds Announce the Arrival of Spring

3-10-15  red-winged blackbird IMG_3155Regardless of the deep snow that remains on the ground and the frigid temperatures we’ve had recently, spring has announced itself with the arrival of red-winged blackbirds this week. Most redwings that breed in New England migrate approximately 500 miles further south to spend the winter. In the spring, males begin migrating first, flying north in flocks during the day to their breeding grounds. (In the fall, females depart first.) While they eat primarily insects during the breeding season, redwings subsist mainly on seeds and grain this early in the season. Before you know it, females will return, and up to fifteen of them will be nesting on the territory of each male (though he doesn’t sire all of the nestlings).

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Pileated Woodpecker Feeding Hole Embellishment

3-2-15  pileated horizontal lines 057Large rectangular excavations in trees, indicating Pileated Woodpecker feeding activity, are relatively common. These holes give the woodpecker access to carpenter ants living in galleries within the tree. What are not common are the horizontal lines radiating out from either side of the top rectangular Pileated Woodpecker feeding hole (and, more subtly, the bottom two holes) in the pictured tree.

Pileated Woodpeckers use methods other than drilling rectangular holes to locate insects – they glean branches, trunks and logs, peck bark and scale bark off of trees. But these lines are unusual, to say the least. If anyone is familiar with this pattern, and would care to explain the function of these horizontal lines, it would be greatly appreciated. After racking my brain and checking several resources, I cannot come up with a plausible explanation, though inevitably there has to be one, for no pileated woodpecker, or any other creature, is about to waste precious energy, especially in a winter as cold as this one. (Thanks to photographer, naturalist and keen-eyed John Snell (http://stilllearningtosee.com/about/) for finding and sharing this discovery with Naturally Curious.)

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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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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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