Acorn Woodpecker and Gila Woodpecker
The typical woodpecker, primarily distinguished by its propensity for pecking bark and diseased wood in a determined search for insects and for excavating deep cavities in trees and columnar cacti for nesting sites, poses complex engineering problems. It must follow its trade while clinging to a vertical surface, chiseling away at several times a second, or thousands of times a day, striking each time like an ice pick, enough, you would think, to rattle its head.
Its body must be designed to serve as a platform for the intense pecking. Its senses must be acute enough to detect, unerringly, the precise location of insects at work in subsurface tunnels or nests. Its brain must be protected from the force of the repeated blows. Its eyes must be protected from flying chips as well as retinal detachment or simply popping out of its skull under the force of the repeated blows. Its tongue must somehow reach like a straw through a small, drilled hole for several inches to reach secreted insect prey.
Woodpeckers’ bodies, or their “physical conformation especially adapts them to this mode of life,” according to the fine old book Birds of America, edited by T. Gilbert Pearson. “Their legs are rather short and stout and the toes are furnished with strong sharp claws. With the exception of the genus Picoides, or Three-toed Woodpeckers, all North American Woodpeckers have four toes, two of which point forward and two backward [permitting them to clamp on to tree bark]. As a further aid in maintaining their hold on the trunks of trees their tails are composed of stiff feathers terminating in sharp spines which can be pressed against the bark and so serve as a prop to hold the bird in an upright position while it is at work.”
The woodpecker’s head especially could stand as an engineering marvel. With its extremely sensitive hearing, the bird can detect insect activity well below the surface of a tree’s bark. Its strong chisel-like beak serves as a formidable woodcutting instrument, often leaving a pile of sawdust to signal its presence. It has a “thick skull with a spongy cartilage at the base of its beak to absorb the force of all that hammering,” said Joe Eaton, writing for the Berkeley Daily Planet, November 21, 2006. “The mandibles the upper and lower jaws are attached to the skull by strong muscles that contract a millisecond before each blow, creating further cushioning.
“The muscles also divert the force of the impact to the base and rear of the skull, bypassing the brain.”
Some woodpeckers have a specially designed “third eyelid” that restrains the cornea when the bill strikes the wood, preventing detachment of the retina or the physical “popping out” of the eyeball.
The woodpecker’s tongue comprises the “most interesting and peculiar point in the anatomy of these birds,” said the Birds of America. Typically, the bird’s tongue begins as two slender filaments extending forward from the back of the skull. One filament curls around one side of the head, the second, around the other side. The filaments join in the vicinity of the eyes, nasal passages or throat, the exact connection point varying with the species of the woodpecker. At the juncture, the tongue assumes a slender, cylindrical shape that terminates in a hard and, in many cases, a barbed point. “The rear end of the tongue,” said the Birds of America, “is enclosed in a muscular sheath by means of which it can be pushed out from the mouth to a considerable length and used as a most effective instrument for dislodging grubs or ants from their burrows in wood or bark.”
In fact, the woodpecker’s tongue, typically several times the length of its beak, provides the bird with a surprisingly effective instrument for feeding. Mark Stewart said, in an ETCSA Internet site article, “Woodpeckers,” that in an experiment with caged woodpeckers, ornithologists “tried holding food above and behind the birds’ heads, and were astonished when they whipped their tongues up over their heads, snatching away the food, without looking around, or turning their heads.”
Our Basin and Range Woodpeckers
Most of our 15 to 18 or so species of woodpeckers, including flickers and sapsuckers, have established year-round homes either generally or regionally in our Southwestern desert basins and mountain ranges, according to Roger Tory Peterson in his Western Birds. Collectively the woodpeckers, usually characterized by an undulating, or “galloping,” flight, range from the desert scrublands to drainages and river bottoms to juniper and oak mountain flanks up to the Ponderosa pine, fir and spruce forest highlands. Our various species, which measure 6 to 14 inches in length, feed, not only on the arboreal boring insects, but also on insects, small reptiles, smaller birds’ eggs, fruit, tree sap and even nuts.
According to Jim Burns, “Arizona’s Special Species: Golden Flicker,” Maricopa Audubon Society Internet site, “Flickers consume more ants than any other North American bird species and thus, though vertical creatures while excavating their homes, they alone among the woodpeckers spend most of their foraging time on the ground in horizontal posture. Because they are ant specialists, flickers have developed even longer tongues, capable of extending five inches outside the bill to probe deeply into anthills.”
Woodpeckers peck, not only on insect-infested trees, they may play tattoos on the wooden siding or shingles or even the rain gutter of your house, on metal or plastic structures along your street, or even on the light posts at your intersections. Apparently, they choose materials that resonate loudly to the drumming, hoping to establish and defend territory, attract a mate or, maybe, just make a racket. They may tap as part of a process of selecting a nest site, making the process a mating ritual. The males and female of some species drum back and forth, alternatively, in a woodpecker version of a romantic duet, according to Amy Salveter, “Missouri Woodpeckers,” Missouri Conservationist Internet site. “Woodpeckers drum to spread woodpecker news,” said Burns, and “the louder the surface the farther the news travels.
Typically, our woodpeckers nest in cavities they have pecked into trees or columnar cacti. “The eggs of Woodpeckers are invariably glossy, immaculate white,” said Birds of America. “They number 4 to 8 and are deposited on small chips at the bottom of the excavation, no attempt being made to construct anything like a true nest.” Typically, nesting pairs of woodpeckers incubate the eggs for about two weeks to a month, when they hatch. The parents share responsibility for brooding and feeding their young, who fledge and leave the nest three or four weeks after hatching and reach full independence a few weeks later.
Among our Southwestern species, the engaging acorn and Gila woodpeckers occur commonly within their pri ncipal territories.
The Acorn Woodpecker
The acorn woodpecker a nine-inch-long bird with a face like a harlequin has a black and white head with a red crown, a yellowish-white throat, a black chin, a black bill and white-encircled eyes. It has a black back with a white rump, black wings with white patches, black-streaked breast and flanks with a white belly, and a black tail. Its white rump and wing patches show prominently when the bird takes flight.
According to Peterson, the acorn woodpecker, which has a distinctive WAKE-up! call, ranges from about the Pecos River westward across Texas, New Mexico and southeastern Arizona and from Oregon southward through western California. True to its name, the bird favors those woodlands with good stands of acorn-producing oak trees, a preference which takes it into river corridors, mountain forests and even urban parks.
The acorn woodpecker, which enjoys the company of other acorn woodpeckers, feeds primarily on an eclectic diet of bees, flying ants, beetles, fruit, flower nectar, tree sap, oak flower clusters (catkins), and, of course, nuts, according to Marie S. Harris, writing for the Animal Diversity Web Internet site.
The bird, with others in the family, picks acorns from the oaks and stashes the nuts, as winter provisions, in “granary trees,” where it has bored storage holes in the bark or dead limbs. The acorn woodpecker, with its family, may drill tens of thousands of the holes into a granary tree over time. The bird may also store piñon pine nuts plus cultivated almonds, pecans and walnuts, according to researchers Peter B. Stacey and Roxana Jansma, writing for The Wilson Bulletin, Vol. 89, No. 1. It wedges the nuts so tightly into the holes that they are difficult for other birds or any animals, for instance, squirrels, to extract, and it and the family collectively defend their food stores with determination. When feeding time comes, according to Michael Givant, writing for the Syosset+Jerico Tribune Internet site, the acorn woodpecker apparently pecks a hole in a horizontal limb, using it as a vice to fix a nut. It chisels open the nut with its bill to gain access to the meat.
While the acorn woodpecker cooperates with its family members to gather, cache and defend winter nut provisions, it can get downright cantankerous with its associates during reproduction, said Harris. Males compete vigorously with other males for feminine attention, sometimes, in a jealous pique, disrupting the mating process. Females compete with other females for nesting privileges, quarreling over space in the communal wood-chip-lined nesting cavity and destroying the eggs of their rivals. Ultimately, however, the birds eventually make peace, turning to the serious business of reproduction. Both males and females incubate the eggs, which hatch after some 11 days. The acorn woodpecker’s entire clan joins together in a renewed spirit of cooperation to feed and nurture the nestlings, which fledge and leave the nest about a month after hatching.
The Gila Woodpecker
The eight-and-one-quarter-inch-long Gila woodpecker more reserved in its costume than the acorn woodpecker has a tan head, throat, breast and belly. It has black and white bars across its back and wings. It has black and white bars across the central feathers of its otherwise black tail. The male wears a red crown. The more demure female wears none. Both the male and female have a white wing patch that distinguishes the bird in flight.
In the United States, the Gila woodpecker, announcing its presence with a noisy, trilling and downright irritating squeak, primarily occupies the Sonoran Desert in Arizona, the southeastern tip of California, and the southwestern corner of New Mexico. It favors the low desert scrublands with saguaro cacti and mesquite trees, where it gleans in bark and cavities to feed primarily on ants, grasshoppers, beetles, berries and saguaro cactus fruit.
While it takes up residence in habitats such as woodlands along river bottoms, pygmy forests along the lower mountain slopes, and the taller trees of established urban neighborhoods, the Gila woodpecker has become best known for nesting in the saguaro and other large cacti of the Sonoran Desert. Both the male and female join to excavate a nest cavity in the saguaro, then leave it alone for several months to dry, allowing the inner pulp to form a solid casing suitable for raising a family. They will defend their nest site against all would-be intruders.
Unlike the polygamous and highly social acorn woodpecker, the Gila woodpecker remains true to its mate and prefers solitude to company during the breeding season. With good food sources, a pair may produce two clutches with three to five eggs each during the spring and summer, according to The Nature Conservancy’s “Species Management Abstract for the Gila Woodpecker.” Both the male and female incubate the eggs, which hatch within about two weeks. Both feed the young, who fledge and leave the nest within about a month but persistently hang around mom and dad’s dinner table for some more weeks. In excavating its saguaro nest cavity, the Gila woodpecker provides quarters for uninvited guests such the “American Kestrel, Elf Owl, Ferruginous Pygmy-Owl, Western Screech Owl, Brown-crested Flycatcher, Purple Martin, Cactus Wren, lizards, snakes, rats, mice, etc,” said the Nature Conservancy.
The Gila woodpecker’s propensity for excavating its nest cavities in the non-woody saguaro cacti should disqualify the bird for membership in the woodpecker fraternity, according to some purists. “To which it may be replied, with equal seriousness and profundity,” said the Birds of America, “that since the bird lives in a country which grows little wood, there is little wood to peck, but from the fact that it pecks the nearest substitute for wood that is available we are justified in concluding that it would peck wood if it could, and therefore, is at heart a Woodpecker.”
If you are an aspiring woodpecker watcher a special sector among the birdwatchers you may hear the bird before you see it, allowing you to follow the sound to the source. You may eventually become able to sort out the species by the pattern of the pecking and the volubility of the voice.
Unfortunately, some species have grown in less populous in some areas, primarily because of loss of habitat, for instance, to forest clear-cutting and urban development, and competition with invasive species, for instance, with the European starling. We would be wary of the woes of the woodpecker, for without woodpeckers, what would woodpecker watchers watch?
by Jay W. Sharp
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