An online resource based on the award-winning nature guide

Raptors

Bald Eagles Nesting

4-9-15  bald eagle and nest 069In the Northeast, Bald Eagles seek out the tallest trees around in which to build their nests. In certain locations in Alaska, coastal California and northern Canada where there are no trees, Bald Eagles will nest on the ground. When building a nest in a tree, eagles will usually build it in the top quarter of the tree, just below the crown, on limbs capable of supporting a large nest. Sticks from the ground are collected up to a mile away from the nest or are broken off of nearby trees. Additional materials are regularly added to the nest throughout the year, including daily additions during the breeding season (see photo).

Many live eagle cams can be found online (in Minnesota, one chick, one egg – http://mnbound.com/live-eagle-cam/ ; in Georgia, older nestlings: http://www.berry.edu/eaglecam/ ; in Pennsylvania, very young chicks: http://www.ustream.tv/decoraheagles ), giving the viewer a window into the incubation, birth and growth of these raptors. Depending on the location of the nest, one can see every stage of development, from eggs to hatchlings to all-but-fledged nestlings. In New England, eggs are soon to hatch, if they haven’t already. (Thanks to Marianne Blake for photo op.)

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Great Horned Owls Incubating Eggs

4-1-15 GHO2  240Great Horned Owls are said to have the widest range of nest sites of any bird in North or South America. Like other owls and falcons, this raptor does not build its own nest, but rather relies heavily on abandoned stick nests of diurnal birds of prey. Red-tailed Hawk nests are often usurped, as well as those of Bald Eagles, crows, ravens and herons. Nests may be lined with shreds of bark, leaves, downy feathers from the owl’s breast, fur of prey and trampled pellets. In addition to bird nests, Great Horned Owls also raise their one to four nestlings (usually two) in tree cavities and snags, on cliffs, in deserted buildings, in squirrel nests and even on the ground.

The female Great Horned Owl does all the incubating; the male delivers prey to her at intervals throughout the night. These early nesters have incubated eggs successfully when outside temperatures have been as low as -27°F. Hopefully warmer temperatures will welcome the newly hatched owlets in about a month. (photo: mostly hidden Great Horned Owl in Great Blue Heron nest)

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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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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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Juvenile Barred Owls Mastering Flight

barred owl-fractured wing 062Typically Barred Owls in northern New England hatch in May and fledge, or leave their nest, in June at approximately four to five weeks of age. Unlike most young birds, Barred Owl nestlings leave their nest before they can fly. They initially perch on the rim of the nest and then climb to a branch on the nest tree, eventually dropping to the ground and climbing a nearby leaning tree to perch. The parents feed their young from the time they hatch until late summer or early fall. The fledglings begin short flights at approximately 10 weeks of age, attaining longer flights by 12 weeks. The pictured Barred Owl may have been mastering flight when it fractured a wing and ended up on the ground, soaking wet and very vulnerable to predation. (Thanks to Bob Moyer for photo op and Vermont Institute of Natural Science’s Wildlife Rehab staff for setting wing.)

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Young Cooper’s Hawks Fledging

8-19-14 juvenile cooper's hawk2 306After a month of living in a nest that measures roughly 7 ½ inches across and 3 inches deep, Cooper’s Hawk nestlings are more than ready to stretch their wings. Although they’ve been dismembering prey (mostly birds and a few small mammals brought to them by their parents) since they were three weeks old, catching prey is a skill they have yet to acquire. For roughly ten days after they leave their nest, the young hawks return to it for continued prey deliveries (and for roosting). During this time the fledglings learn to catch their own prey and they become independent, but they continue to stay together near their nest for the next month or so. (Thanks to Marian Boudreault for photo op.)

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Broad-winged Hawks Become Empty-Nesters

8-7-14 broad-winged fledgling2 037Broad-winged Hawk nestlings typically leave their nest sometime in July or early August, at about five to six weeks of age. The fledglings tend to stay within their parents’ territory for up to eight weeks. Much of the first two weeks after fledging is spent perched close to the nest, often returning to the nest for food delivered by the parents, but by the time the fledglings are about seven weeks old, they are capturing their own prey. This leaves the adults free to hunt for themselves, as they fly overhead emitting their high-pitched, shrill whistle. (Photos: adult Broad-winged Hawk)

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