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Woodpeckers

Red-bellied Woodpeckers Sunning

7-20-16 male red-bellied adult 173Red-bellied Woodpeckers have extended their breeding range northward and westward over the last 50 years and are now breeding in northern New England.  Many are year-round residents here, while some individuals move further south during particularly harsh winters.  This range extension allows for observations not possible even 10 or 20 years ago.

While watching a Red-bellied Woodpecker this summer, I witnessed behavior I had never observed before.  The bird flew repeatedly to the same tree branch, flattened itself on the branch with its body facing the sun and then fanned its wings out while cocking its head, raising its crown feathers, opening its beak and appearing to look at the sun.  This behavior is common enough to have a name – the woodpecker was “sunning” itself.  While preening, stretching and calling often takes place intermittently while the bird is engaged in sunning, it may also enter a stupor or state of lethargy.   (Thanks to Cindy Lawrence for photo op.)

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Changing of the Guard: Hairy Woodpeckers Sharing Parental Duties

5-30-16 hairy woodpeckers  215

When their offspring are very young, Hairy Woodpeckers feed them by regurgitation.  As the nestlings mature, the parents bring food back to the nest.  Most species of birds (85%) engage in bi-parental care, where the male and female contribute equally to feeding and guarding their young.  Often the male does more of the food gathering and the female more of the brooding.

In some of these species the male and female both brood as well as gather food.  Hairy Woodpecker parents share these duties equally for the month that their young remain in their cavity nest.  They both brood their young, with males typically getting night duty, and both gather food for their nestlings.  Lawrence Kilham, a New Hampshire MD and ornithologist, found that male Hairy Woodpeckers foraged farther from the nest, made fewer feeding visits, and brought larger prey to nestlings, whereas females remained closer and fed young three to four times as frequently as males.  (Photo: female Hairy Woodpecker arriving with arachnid food, male about to depart. Thanks to Suzanne Weinberg for photo op.)

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Yellow-bellied Sapsuckers Drilling Wells & Lapping Sap

4-26-16 yellow-bellied sapsucker 191

Yellow-bellied Sapsuckers have returned and in between sending their Morse code messages, are drilling into over 1,000 species of woody plants to obtain sap.  At this time of year, sap wells are drilled into xylem tissues (transport water and nutrients from roots to branches) to feed on sap that is moving upward; after deciduous species leaf out, sap wells tap phloem tissues (transport sugars and other nutrients made in the leaves to other parts of the tree).  Unlike sap drawn from the xylem which contains from 2-3% sugar, phloem sap may contain 20-30% sugar.

Sapsucker tongues have a fringe of hair-like projections along the edges which enable the sapsucker to lap up the sap that accumulates in a well (“saplapper” would be a more accurate name for these woodpeckers).  Recently a female sapsucker landed on the trunk of a nearby Sugar Maple and tapped eight wells.  She then spent the better part of the afternoon inserting her brush-like tongue into the wells and drinking the sap that collected.  The entire time she was drinking sap, she was constantly (8 times per hour) evacuating a stream of clear liquid (as opposed to the typical uric acid excreted by birds).  Apparently much of what goes in must come out.

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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 (http://stilllearningtosee.com/about/) 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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