American Crow Diet & Hunting Techniques
One would be hard pressed to name all of the different types of food that American Crows consume. The diet of these omnivorous birds runs the gamut — small birds, bird eggs and nestlings, tadpoles, frogs and toads, snakes, turtles, small mammals, fish, insects, clams, nuts, fruits and carrion.
Crows use a number of techniques in obtaining their food. They find most of it as they’re walking on the ground, occasionally they probe just under its surface. You often see them lifting and flipping leaves, cow pies, sticks and small stones to see what creatures live beneath them. Crows have also been known to stand belly-deep in water as they hunt for fish. In addition, they sometimes hunt from a perch, pouncing on prey they see, and catch flying insects and small birds on the wing. Crows have even been observed using “tools” such as pieces of wood to probe for insects.
If their prey is large, crows will place it under one or both feet and tear pieces off with their bill (see pictured American Crow with road-killed Eastern Chipmunk it retrieved).
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American Crows Building Nests
Congratulations to Robyn Deveney and Chris Wings, the first Naturally Curious readers who accurately suggested the Mystery Photo depicted the tracks of an American Crow collecting nesting material. As I approached the pictured area, I flushed two black birds who were soon cawing and flying overhead, with a stick protruding from one of their beaks.
Crows are one of the earliest passerine, or perching, birds to engage in nest-building and egg-laying. Crows tend to build new nests each year, seldom reusing a nest from a previous year. In New England both members of a pair are busy collecting nesting material such as sticks, bark strips, weeds and mud, in March. They bring this material back to the nest site, which is typically a conifer, and construct a bulky nest usually in the crotch of the tree or on a horizontal branch. It takes anywhere from one to two weeks for crows to complete a nest and up to six days to lay 2 – 6 eggs. Incubation typically begins in early April.
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Snapping Turtle Nests Raided
Female Snapping Turtles spend a lot of time and effort finding suitable sandy soil in which to dig their nest and lay their eggs. Some turtles have been found laying their eggs as far as a mile from the nearest water source. Once she has laid her eggs and covered them with soil, the female snapper returns to her pond, leaving her eggs to hatch on their own, and the hatchlings to fend for themselves.
It is estimated that as many as 80 to 90 percent of all turtle nests are destroyed by predators, weather conditions and accidental disturbances. Most of the damage is done by predators – skunks, raccoons, foxes, crows, among others. Most nests are discovered by smell, and most are raided at night. The fluid that coats the eggs, that is lost by the mother during egg laying or is lost through breaks in the eggs, produces a smell that is easily detected by predators. While a majority of nest raids happen within the first 48 hours of the eggs being laid, studies have shown that predation occurs over the entire incubation period (June – September). The pictured Snapping Turtle nest was dug up and the eggs consumed 10 days after they were laid.
If you are aware of a spot where a turtle dug a nest and laid eggs, you can try to protect the nest from predators by placing either a bottomless wire cage or an oven rack over the nest site, and putting a heavy rock on top. The tiny hatchlings will be able to escape through the openings but hopefully, if the rock is heavy enough, raccoons and skunks will become discouraged and give up trying to reach the nest.
The next Naturally Curious post will be on 7/5/17.
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Sentinel Crows
Ornithologists have noted that especially during the winter, American Crows assign one or more of their flock to keep watch over the rest of the group, or “murder,” as they feed on the ground nearby. While acting as sentinels, the crows will call frequently, even when predators are not present. When they intensify their calling, the crows that are feeding often flush.
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American Crow Bills Used As Tools
American crows obtain most of their food on the ground as they walk along in search of seeds, insects, frogs, snakes, bird nests and small mammals. Their hunting techniques are varied and most involve the use of their bill. In search of invertebrates, crows will probe the soil with their bill, flick aside leaves, dig in the soil and even lift cow paddies. They fish for tadpoles and dig nearly an inch deep with their bill for clams. In winter, their foraging continues and as these tracks indicate, when the snow is only a few inches deep they will walk around and around in a given area, probing tufts of grass for hibernating insects, mice, voles, or any other form of life these opportunists find.
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Great Horned Owls Incubating Eggs
Great 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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Crabapple Consumers
Even without much of anything to go on, all answers were correct! Although Cedar Waxwings were the predominant avian visitor to this crab apple tree when I visited it, there were also robins, starlings and crows feasting away (and presumably several other species, including turkeys, as some of you guessed, at other times).
Cedar Waxwings are among the most frugivorous (fruit-eating) birds in North America. In the winter, sugary fruits dominate their diet to such a degree that occasionally, when the fruit has become overripe and has started to ferment and produce alcohol, the waxwings can become intoxicated and, rarely, die. One individual saw that her front lawn was littered with the bodies of dead Cedar Waxwings on top of the snow, but by the time she went out to dispose of them, the drunken birds had all revived and flown away.
During the winter, Cedar Waxwings travel in flocks of up to several hundred birds. They are nomadic, roaming the countryside in search of crab apples, hawthorns and mountain ashes, as well as serviceberry, juniper, winterberry, dogwood and cedar, among others. Waxwings will descend upon a tree en masse and while perched will bend down and pluck crab apple after crab apple, swallowing them whole, one at a time. Occasionally you will see them hovering briefly in the air while plucking fruit. They are well known for “gifting” fruit to fellow waxwings.
Many birds that eat a lot of fruit separate out the seeds and then regurgitate them. Cedar Waxwings let the seeds pass through them, scarifying the seeds in their digestive tract (breaking down their outer seed coat), which, once the seeds are deposited, allows them to eventually germinate. Because of this, waxwings are considered important seed dispersers for many fruiting plants in North America (including the invasive, non-native honeysuckle which, when eaten during the time feathers are developing, causes Cedar Waxwings to develop orange, not yellow, tail bands).
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Nictitating Membrane Provides Moisture & Protection to Eyes
You and I have two opaque eyelids, one above the eye and one beneath. When we blink, they meet in the middle of our eyes. Some birds, amphibians, reptiles, fish and mammals have three eyelids – two similar to ours, and a third translucent or transparent eyelid, called a nictitating membrane. This membrane moves horizontally across the eye from the inside corner to the outer edge of the eye, much like a windshield wiper, when needed for protection, to clear debris or to moisten the eye. Although this American Crow’s nictitating membrane looks as if it was blinding the crow, it isn’t. Because of the membrane’s translucency, the bird can still see when the membrane is covering its eye.
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Ruffed Grouse on Nests
A Ruffed Grouse’s nest is pretty basic – just a shallow bowl on the forest floor, created by the hen grouse tossing leaves over her shoulder and having them fall on her back, slip down to the ground and form a bowl. Ruffed Grouse lay anywhere from 9 to 14 eggs at intervals of 25 to 30 hours, which means it takes about two weeks for a hen to lay an average clutch of 11 eggs. Each of her eggs weighs about 4 percent of her body weight — the entire clutch will be equal to about half of her weight. Once incubation starts (when the last egg is laid) the hen’s behavior goes from wandering around and feeding voraciously, to sitting on the nest and barely moving. Because of this behavior, as well as her cryptic coloration, an incubating Ruffed Grouse hen is much more likely to see you before you see her. She will stay motionless on her nest, even in the face of danger, hiding her eggs. Once she is certain she has been spotted, she will fly off the nest, exposing her eggs. Foxes, crows, ravens, chipmunks, skunks, bobcats and raccoons are some of the predators responsible for the loss of 25% – 40% of grouse nests each year. After the precocial Ruffed Grouse chicks hatch during the first two weeks of June, they will be led away from the nest site by the hen. Within 24 hours they will be feeding on insects and within a week they may double their weight! (Thanks to Ginny Barlow for photo op.)
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