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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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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Tom Turkeys Strutting Their Stuff
Congratulations to Penny Jessop, who submitted the first correct Mystery Photo answer!
In the Northeast, male Wild Turkeys begin gobbling and strutting in late February. Their courtship ritual usually starts before females are receptive, and continues into late March and early April, when mating typically takes place.
At this time of year males are bedecked with blue wattles (flap of skin on throat) and snoods (fleshy piece of skin that hangs over beak), and bright red major caruncles (bulbous, fleshy growths at the bottom of the turkey’s throat). Displaying these adornments while slowly gliding around a female, the male fans his tail, lowers his wings with the primaries dragging on the ground/snow (these primary wing feathers are responsible for the parallel lines either side of the trail of tracks), elevates the feathers on his back and throws his head backward the female. If she is receptive, she lowers herself and crouches on the ground, signaling to the male that he may mount her.
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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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Bird Nests: Look But Don’t Collect
It is prime time to look for bird nests now that leaves have fallen and heavy winter snow has not arrived. Nests such as this Mourning Dove nest are visible and still in fairly good condition. Much can be learned from examining the habitat, exact location, size, shape and construction material of these avian nurseries. But the nests must be left where they are, for possession of not only a bird, but 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.
Ninety-seven years ago the Migratory Bird Treaty Act (MBTA), one of our oldest wildlife protection laws, was created. Basically it is a law that protects birds from people. It was made in response to the extinction or near-extinction of a number of bird species that were hunted either for sport or for their feathers. According to the United States Fish & Wildlife Service (USFWS), “The MBTA provides that it is unlawful to pursue, hunt, take, capture, kill, possess, sell, purchase, barter, import, export, or transport any migratory bird, or any part, nest, or egg or any such bird, unless authorized under a permit issued by the Secretary of the Interior.” A list of the species this law pertains to can be seen at http://www.fws.gov/migratorybirds/RegulationsPolicies/mbta/MBTANDX.HTML.
Not all North American bird species are protected under the MBTA. (Passenger Pigeons were not protected, and they no longer exist.) Birds that are considered non-native species such as the House Sparrow and the European Starling are not protected, and many hunted or game birds, including ducks, geese, doves, and many shorebirds are subject to limited protection and can be hunted in season.
The U.S. Fish and Wildlife Service is currently working on strengthening this bill to better protect birds from modern-day threats (windmills, cell phone towers, etc.). According to USFWS estimates, power lines kill up to 175 million birds a year. Communications towers account for up to 50 million kills, and uncovered oil waste pits account for up to another 500,000 to 1 million deaths. Data on wind turbines are harder to come by, but current estimates are around 300,000 bird fatalities a year. A number of companies in the oil and power-line sectors have already developed and implemented best practices to protect birds. Let us hope that this trend continues.
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Pileated Woodpecker Droppings
Pileated Woodpeckers usually defecate frequently during the day at their foraging sites. As they pry off long slivers of wood to expose carpenter ant galleries, the wood chips pile up on the ground. A substantial pile usually indicates that the woodpecker has been working long enough at this site for there to be some droppings in the pile.
Pileated Woodpeckers eat ants, primarily carpenter, and beetle larvae throughout the year. Fruit and nuts are eaten when available. The primary food shifts seasonally, with fruit mainly in the fall, carpenter ants in the winter, wood-boring beetle larvae in early spring, and a variety of insects in the summer.
Like humans, birds excrete metabolic waste products, mainly nitrogen, which remains after food is broken down. Humans excrete waste nitrogen as urea in urine, which is diluted with water. Birds, needing to be as light as possible for efficient flight, do not have heavy, water-filled bladders. They excrete nitrogen as a chemical called uric acid in a concentrated form with no dilution necessary. The white outer coating of bird droppings is uric acid. The insides of the droppings are the actual feces, or the indigestible parts of a bird’s diet. A Pileated Woodpecker’s droppings at this time of year consist of bits of carpenter ant exoskeletons and a surprisingly small amount of wood fiber (see insert). Birds simultaneously evacuate uric acid and feces from an opening just under the tail called the cloaca or vent.
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Woodpeckers Bark Sloughing
Several species of woodpeckers search for wood-boring beetle larvae by removing the bark from a tree (in addition to drilling holes). This is referred to as bark sloughing. Some birds, such as nuthatches, remove only scales of bark, not the whole layer like woodpeckers, and this is referred to as scaling. After finding or creating an opening, a woodpecker repeatedly slips its pointed beak under loose bark, prying it off of the tree. It then uses its long, barb-tipped tongue to capture the exposed insects. Different woodpecker species tend to feed on either trunks or branches, and at different heights. Initially sloughing can resemble the work of porcupines, but close examination can reveal the marks of a beak, which are perpendicular to the trunk or limb, rather than the grooves left by a beaver’s incisors.
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Baltimore Orioles Building Nests
Once the female Baltimore Oriole has selected her mate, she chooses a nesting site within his territory, often the tip of a slender outer tree branch, as it’s relatively inaccessible to predators. The female usually builds the nest by herself, taking 4 – 15 days to complete it. The first few fibers are wrapped loosely around branches. With apparently random poking, knots and tangles are created in these fibers. The female than adds more fibers, one at a time, to extend, close and line the nest. Somewhat miraculously, after days of laborious work, the nest takes on its gourd-like shape. Initially the weaving of fibers from plants such as grasses, milkweed stems or grapevine bark can be observed (horse hair, twine and synthetic fibers are also used). Towards the end, when the nest lining is added, the bird is hidden inside the nest and all that’s visible is the periodic bulging of the nest where she is applying softer material (often cottonwood or willow seed fluff, milkweed seed plumes or feathers) to cushion her eggs and nestlings.
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Avian Toe Arrangment
As opposed to humans, who use the entire bottom of their feet for support, birds stand and walk only on the ball of their foot and with their toes. When you look at a bird’s leg, what appears to be its knee, bending backward instead of forward as it does in humans, is actually its heel.
Most birds have four toes, arranged differently according to the life style of the bird. Songbirds, as well as most other birds, have three toes pointing forward and one pointing back. Most woodpeckers, being active climbers, have two toes pointing in each direction, which provides added clinging support. The outer toe (of the three forward toes) of ospreys and owls is reversible, so that they can have two toes in back should they need to get a better grasp on slippery fish or other prey. Some birds that do a lot of running, such as sanderlings and most plovers, have only the three forward toes. (Photo: Mourning Dove tracks)
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Ruffed Grouse Wings
You can often determine the type of flight that a bird is capable of by looking at the shape of its wings. Long, narrow wings are excellent for gliding, while the short, rounded wings of a Ruffed Grouse allow for tight maneuvering in the dense forests where they live. The shape of their wings and their quick-contracting muscles equip grouse for the short bursts of high speed (not long distances) they take when feeding or evading predators. (Photo: a Ruffed Grouse walked a short way and then took flight, beating its wings against the snow twice before it was airborne.)
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Ruffed Grouse Snow Cave
When snow depth is over 10” Ruffed Grouse are known to dive into it and often burrow a short distance in order to seek refuge from the wind and the cold as well as from predators, a behavior known as “snow roosting.” Because the grouse flies into the snow leaving no tracks and little scent, predators have difficulty detecting them. The major risk is freezing rain which can form a crust on top of the snow, trapping the grouse. The Ruffed Grouse’s behavior allows it to conserve a great deal of energy, as the temperature inside this roost rarely falls beneath 20°F. This conservation of energy translates into less time spent up in trees eating buds, exposed to hawks and other predators. When morning comes, the grouse usually bursts out of the snow, leaving a hole and wing marks, or, as in this case, shuffles its way to the surface of the snow before taking off. The presence of scat indicates that the left-hand cavity in this photograph is where the bird bedded down and its exit was made to the right. (Thanks to Edith Hoose for photo op.)
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Barred Owl Story in the Snow
These beautiful impressions in the snow tell the story of a Barred Owl diving feet first after prey, most likely a vole or mouse. The fact that there are no rodent tracks on the surface of the snow tells you that the mouse or vole was well hidden in its tunnel under the snow at the time. Apparently the owl’s talons did not reach their target (at least, no blood or rodent remnants), and the owl continued to plow through the snow in repeated attempts to capture its prey before taking flight.
The presence of facial discs (feathers in the shape of a funnel around each eye that direct sound waves towards the owl’s ear) plus the differing size and asymmetrical placement of an owl’s ear openings allow the owl to discern the direction a sound is coming from, how far away it is and its height relative to the owl – even in the dark or under the snow! The exceptional hearing ability of owls, particularly those in the genus Strix (which includes Barred and Great Gray Owls), enables them to plunge into the snow and often successfully capture prey, sight unseen. (Species of owl was determined by wing length. Thanks to Rob Anderegg and Jennifer Grant for photo op.)
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The Butcher Bird
The Northern Shrike (Lanius excubitor) is highly unusual in that it is a predatory songbird. Birds, mammals and insects are preferred over nectar, nuts and seeds. This tundra-nesting bird comes as far south as New England to overwinter, where it preys mainly on mice, voles and small birds. The Northern Shrike often kills more prey than it can immediately eat or feed its young, storing the excess food to eat later, when available living prey may be scarce. The manner in which it stores this extra food is what gave it the name “butcher bird;” it often impales prey on a thorn, broken branch (as in photograph) or even barbed wire, or it wedges prey into narrow V-shaped forks of branches, where they hang until reclaimed by the shrike. (Impaled mouse photo by Bridie McGreavy; northern shrike photo by MS Henszey)
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Pileated Woodpecker Sign
Pileated Woodpeckers typically make rectangular holes in trees in order to reach the carpenter ants that live in galleries they’ve created deep within a tree. While ants are high on a Pileated Woodpecker’s list of preferred food, wood-boring beetle larvae are not far behind. Sometimes the exertion of jackhammering isn’t necessary in order to reach insect larvae – removal of the outer bark is enough to expose tasty morsels.
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