An online resource based on the award-winning nature guide

Bird Sign

American Crow Bills Used As Tools

1-13-16  American crow tracks 147American 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

11-23-15 mourning dove nest2  005It 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

11-12-15 pileated droppings 015Pileated 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

woodpecker bark peeling IMG_0567Several 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

6-13-14  b.oriole nestOnce 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

3-17-14 mourning dove tracks 004As 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

2-25-14 grouse wing imprints  010You 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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