There are roughly 85 species of North American birds that are cavity nesters – birds that excavate nesting holes, use cavities resulting from decay (natural cavities), or use holes created by other species in dead or deteriorating trees. Many of them get a jump start on open-nesting birds, due to added protection from the elements. Barred owls, titmice, chickadees, wood ducks, woodpeckers, bluebirds, mergansers – many have chosen a nest site and are busy excavating, lining a cavity or laying eggs long before many other species have even returned to their breeding grounds.
The reduced risk of predation a cavity nest experiences is reflected in several ways: many cavity-nesters have larger clutches of eggs than open-nesting birds and cavity-nesting young also spend a relatively longer period of time in the nest before fledging. When in the woods, keep an eye out for snags (standing dead trees) and stumps, for they provide housing for many cavity-nesting birds. (Photo: Black-capped Chickadee removing wood chips from the cavity it’s excavating in a rotting stump.)
Non-vocal communication between woodpeckers has become apparent in the last week or so — hairy woodpeckers have started to hammer out bursts of steady staccato drum beats on nearby trees. Both male and female woodpeckers drum year round, but they do so most intensively from January to May, especially during the courtship and early nesting seasons which begin in March. Woodpeckers drum for a variety of reasons: defending territory, attracting a mate, maintaining contact with a mate, signaling readiness for copulation and summoning a mate from a distance. Woodpecker pairs also engage in duet drumming, which is thought to play a role in nest site selection and in promoting and maintaining the bond between mates.
If you are hearing but not seeing a woodpecker drumming, it is possible to identify the species by the pattern and pace of its drumming. According to ornithologist David Sibley, the drum of the Hairy Woodpecker is extremely fast and buzzing, with at least 25 taps per second, but has long pauses of 20 seconds or more between drums. The Downy Woodpecker drums at a slower rate, only about 15 taps per second, and drums frequently, often with pauses of only a few seconds between each drum. (Photo is of a female Hairy Woodpecker.)
Red-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.)
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.)
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.
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.
Large 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.)