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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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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 ( for finding and sharing this discovery with Naturally Curious.)

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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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Bark Scaling

12-11-12  bark scaling 024There are two main ways that woodpeckers and occasionally other birds remove bark in search of insects beneath it. One is bark sloughing, where a bird pries off the entire dead layer of bark on a tree (see NC post on 12/5/14). Another method of locating insect larvae that both woodpeckers and nuthatches employ is the removal of individual scales of bark. This is referred to as bark scaling. The pictured hairy woodpecker has removed much of the bark of a dead eastern hemlock using this method.

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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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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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White-tailed Deer Scavengers

deer carcass2  028According to NPR, each year Americans waste 33 million tons of food (and much of this ends up in landfills where it produces methane, a potent greenhouse gas). This situation is totally alien to that of other animals in the natural world, which seem to find a use for any and every organic particle. Great crested flycatchers incorporate shed snake skins into their nests, beavers build dams and lodges with branches they have eaten the bark off of, ermine line their nests with the fur and feathers of prey — the list goes on and on. When it comes to food, there is equally little waste. The carcasses of animals do not linger long, as almost every atom of their bodies is recycled. Fishers, coyotes, foxes, raccoons, opossums, bald eagles, hawks, woodpeckers, ravens, crows and many other animals make short work of a dead deer in winter. Come spring, if there’s anything left, the final clean-up crew consists of legions of turkey vultures, beetles, flies and bacteria, among others. How unfortunate we’ve strayed so far from a process that’s worked for so many for so long.

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