Thursday, January 1, 2009

Woodpecker Series - Part III

The American Three-toed Woodpecker - Picoides dorsalis are widely considered barometers of the health of old-growth conifer forests in North America, due largely to the species’ apparent dependence on mature and old-growth conifer forests. However, because of their low abundance, habitat choice and generally quiet behavior, it is seen only infrequently and has received little attention from researchers.

On the basis of genetic and voice differences, Old and New World populations of Three-toed Woodpeckers are now considered separate species. Picoides dorsalis and P. articus in the US, and P. tridactylus in Europe and Asia, reflect these changes. In 2003 the “Three-toed Woodpecker” was split into the American Three-toed and Eurasian Three-toed Woodpecker. Nearly identical in appearance, they differ in voice and mitochondrial DNA sequences.

The Three-toed Woodpeckers are the only woodpecker common to both Old and New Worlds. It breeds further north than any other woodpecker. There are, currently, eight subspecies (3 Neartic and 5 Palearctic) recognized, although recent molecular data have revealed species-level distinctiveness between a subset of the Nearctic and Palearctic subspecies. This woodpecker is similar to other North American Picoides in having a heavy, chisel-like bill and comparable facial markings and similar to the Black-backed Woodpecker (P. arcticus, previously called the Artic Three-toed Woodpecker) in having three, rather than four toes, and an absence of any red feathering. The males of these species carry yellow feathering on their heads…apparently giving it a somewhat indiscreet history:


"The Indians dislike this bird. They call it . . . “Tikelklala.” They have a legend that this bird, many ages ago, in a time of famine, devoured his mate, and wiped his claws clean on the back of his head; in proof of which, they point to the yellow mark of the “fat,” which remains till this day."

W. H. Dall and H. M. Bannister, 1869

This species’ association with spatially unpredictable disturbance and its large home range make it sensitive to timber harvesting (removal of habitat) and forest fragmentation; both ultimately reduce food availability. Given these habitat requirements, timber harvesting, especially of old-growth coniferous forests, has undoubtedly contributed to population declines in
North America

In Qu├ębec’s black spruce-diminated forests, habitat loss due to timber harvesting may often be permanent as Three-toed Woodpeckers are restricted to forests older than scheduled cutting rotations. In Finland, Three-toed Woodpecker density was significantly correlated with the proportion of forest in nature reserves. Areas with more than 100 yr old, large old-growth tracts, the species had not declined, but in smaller old-growth forests, isolated as a result of logging, the species had declined or disappeared.

Forestry practices such as fire suppression, salvage logging (the removal of burned trees) and suppression logging (the cutting of insect infested trees), remove trees on which this species depends. Additionally, the alteration of natural fire intensity, or the replacement of ‘cool’ understory fires to intense stands, contributes to the decline. Historically, forested areas in the northern Rocky Mountains experienced large, intense fires every fifty to one hundred years. No more.

Three-toed Woodpeckers seem very tolerant of humans, so disturbance by people is an unlikely factor to declining populations of this bird.

Appearance

The Three-toed Woodpecker is a medium-sized black and gray woodpecker. Peter Dunn has referred to this bird as the ‘Shabby Three-toed’ and calls the closely related Black-backed Woodpecker the ‘Sharp-dressed Three-toed’. With a black tail with white outer tail feathers, and black heads with white mustachial and (usually) post-ocular stripes, they can be distinguished from Black-backed Woodpeckers by the barring on their backs and by their slightly smaller size. Their foreheads are also speckled with white rather than being all black like those of Black-backed Woodpeckers, and their white head stripes and yellow crown-patches are less clearly defined. Their grayish-white under parts and flanks spattered with dark barring – enhancing the overall sense of shabbiness.

The distinguishing characteristic of this species is the white “ladder” on its back. The female does not have the yellow cap, but their backs do have the white ladder. Mature birds have white under parts heavily barred with black on the sides and flanks. Upperparts are black, though the primaries are barred with white. The center of the back includes varying amounts of white, as do the outer tail feathers. Its head is mostly black with a white chin and throat and two white stripes; from the base of the bill, below the eye, to behind the ear-coverts and another, which may be more narrow or fainter, extends from behind the eye to the back of the neck. The crown of the male is a yellow patch bordered by white streaks; in the female it is entirely streaked with white, without any yellow at all. Adult plumage is similar throughout the year.

It is most often confused to the Black-backed Woodpecker, with which it is closely related and shares both similar plumage, as well as distribution …though the Black-backed is slightly larger. In addition, the Black-backed Woodpecker has a solid black back and only a trace of white behind the eye; making the upperparts much blacker, overall.

Juveniles are similar to adults but overall duller in color with brown and gray-brown washes. Both sexes may carry a few yellow tipped feathers on the crown…though even if fully yellow, the patch is smaller than that of an adult male.

A female Hairy Woodpecker could be mistaken for a Three-toed, but the Hairy has more white on the head and wing-coverts and no black barring on the flanks; making the lack of contrast between upper and lower parts more distinct in the clean-cut Hairy. It is shaped like Hairy, but has a more oval, rather than square, head and its bill is slightly larger.

The bill of the Three-toed Woodpecker is relatively long, straight and chisel-tipped; eyes are reddish brown; and of course the bird has only three toes…two forward and one back, just like the only other three-toed woodpecker, the Black-backed woodie.

There is marked variation across the entire range, both in proportions of black and white plumage, and also in size. Generally southern populations are darker in color and larger in size.

Stats:

  • Size: 8 – 8 ¾ inches
  • Wingspan: 15 inches
  • Weight: 2.29 ounces
  • A medium-sized black-and-white woodpecker, more black than white.
  • Head is black with a white mustache stripe and a thin white line behind eye.
  • Throat, breast, and belly are white.
  • White flanks with black barring.
  • Back is white or white barred with black.
  • Rump is black.
  • Black tail with white outer tail feathers.
  • Black wings marked with white spots
    on flight feathers.

Habitat

The Three-toed Woodpecker is found in boreal forest (or taiga belt) to tree limit in Alaska and Canada; in the Rocky Mountains south to Arizona and New Mexico, and in Cascades to Oregon. In the eastern United States it is found in Adirondack Mountains of New York, and extreme northern New England. During winter, it is primarily resident throughout breeding range, but may winter at lower elevations. Occasional individuals found south of breeding range. It prefers boreal and montane coniferous forests, especially mature forests with an abundance of insect-infested snags and dying trees; and the same in spruce forests. It is an ardent user of forests disturbed by disease, fire, flooding and other disasters, though perhaps less so than Black-backed Woodies.

The Three-toed Woodpeckers prefers spruce forests, the Black-backed likes spruce as well as other coniferous forests. This habitat difference reflected in this distribution of these two closely related species. This woodpecker, like the Black-backed (and to a lesser degree the Hairy Woodpecker), is associated with locally abundant insect outbreaks, often the result of fire. The Three-toed prefers bark beetles, while the Black-backed specializes on wood-boring beetles. While both species are irruptive, their irruptions probably reflect outbreaks in favorite-food infestations.

The logging of forests damaged by fire, insects or even wind-storm blow-down, make the bird vulnerable to fragmented forests. Fire suppression and the salvage of trees by logging fire-damaged areas and areas damaged by insects reduce the abundance of this species favored food…and so the bird itself. Obviously spraying insecticides hurts, as well.

While boreal and montane coniferous forests are preferred by the Three-toed Woodpecker, it especially prefers mature or old-growth forests with a large amount of insect-infested snags and dying trees. It often inhabits moist-to-swampy areas; wet forests may best describe the preferred micro-climate of this species. It prefers denser forests than the Black-backed Woodpecker, though it may occupy more open areas in the wintertime. During irruptions, it is often found in urban areas.

This bird is normally a permanent resident, but northern birds may move south and birds at high elevations may move to lower levels in winter. It is likely to give way to the Black-backed Woodpecker where the two species compete for habitat.

Concentrations of this species occur in recently burned areas (within 3 yrs) and forests heavily damaged by bark beetles. Cohabitants include Black-backed Woodpecker, Western Wood Pewee, Olive-sided Flycatcher, Gray Jay and Boreal Chickadees.

Food

The Three-toed Woodpecker feeds primarily on the larvae of bark beetles and the larvae of wood-boring beetles, as well as other insects, with some fruit, minimal vegetable material (cambium), and sap, when they visit sapsucker wells; sexual differences in diet
has been noted. Foraging birds work trees tenaciously hammering and flaking off bark. Birds often return to the same trees until the bark is stripped, an indicator
of their presence. It forages mostly on trunks rather than on branches or fallen logs and is not known to
store food.

Big infestations of wood-boring insects concentrate the bird in these areas; the three-toed takes full advantage of the bonanza. In areas where there has been an explosion of the bark beetle, they often provide the most effective control of that major forest pest.

Behavior

This species is often described as tame or easy to approach, but quiet and difficult to find; it is generally uncommon (or even rare) and local. These traits make it difficult to track population trends, though in North America data suggests the bird is declining just as it is in northern Europe.

Again, because of the low abundance of the species, seasonal movements are difficult to track. There is no regular north to south migration, but as with many species winter observations suggest movement may occur. Also, there is regular dispersal of juveniles in fall and early winter. These woodpeckers can also be irruptive, though irruptions are sporadic and localized and mainly occurring in eastern North America. This bird is less irruptive, travels shorter distances and moves later than the Black-backed Woodpecker…and again the irruptions of the two species is not always coincident.

They often perch against tree trunks, and are usually solitary, although pairs may forage together. Similar to most Picoides; this bird spends most of foraging time clinging to and climbing vertical surfaces of trees. Like Black-backed Woodpeckers, they scale the bark off dead and dying trees while foraging, a behavior that often reveals their presence in an area. However, it works higher up on the trunk than the Black-backed woodies…and are reported to favor trees only moderately, not wholly, blackened by fire. This makes sense…their plumage nearly replicates the bark pattern of fire-scored—not scorched and blackened—trees.

Not shy, often allows close approach. Though it does not respond well to pishing, author Stephen Brown discovered he had often been able to coax them quite close by tapping a twig against a tree trunk.

Quick and nimble, the Three-toed’s wing beats are somewhat crisp and stiff; though it undulates through the air like other woodpeckers.

In winter and in cold, wet weather it frequently roosts in old nests, especially if wounded or pursued.

Breeding

Bogs and logged areas with dead standing conifers make good breeding areas for the Three-toed Woodpecker. They form monogamous pairs and often stay together for more than one season. Typically they raise only a single brood each year.

Nesting season begins with much tree drumming by the male, which attracts females and informs other males of his territorial dominance. He also does a lot of head swaying and calls more loudly than usual.

Nesting habitat includes coniferous forests or logged areas and swamps. A cavity nest is dug by both sexes and is placed 5 to 50 feet high in a stump or other dead or dying tree, and often near water. The entrance is about 1 ¾ by 2 inches), and the cavity is about 10 to 15 inches deep.

Nests are built in May and June; the female generally lays four eggs in the nest; both the male and female share the incubation of them. Incubation occurs for two weeks and the young will fledge the nest 22 to 26 days after hatching; by early August. Eggs laid, hatch in two weeks…more than three weeks till they take first flight from nest. It is another four to eight weeks before they are totally on their own. The young are flying and independent by late July or so.

Parents appear to divide the brood as it fledges. Young often sit quietly waiting for adults to come to them, but will also fly after adults; the family maintains regular vocal contact. While being fed, fledglings call loudly with gaping bill.


Interesting Facts

The American Three-toed Woodpecker breeds farther north than any other American woodpecker. The closely related Eurasian Three-toed Woodpecker is the only woodpecker in the world that extends farther north.

The "Three-toed Woodpecker" was split in 2003 into the American Three-toed and Eurasian Three-toed woodpeckers. The two species are nearly identical in appearance, but differ in mitochondrial DNA sequences and in voice

Most woodpeckers have four toes on each foot. The three-toed and Black-backed woodpeckers have only three. The loss of the fourth toe may help deliver stronger blows, but at the expense of climbing ability.

Sound

The call of this woodpecker is a sharp ‘wik’ that closely resembles the Downey Woodpecker. Its drumming is variable; usually short and unfrequently given.

Behavior and calls are less developed than that of the Black-backed, with whom the Three-toed is often confused. The Three-toed has a higher-pitched, longer and less metallic call. Drumming is also slower and shorter than that of the Black-backed.

Sources: Photos:

3 comments:

Debbie said...

Thanks, Beverly. I know this one has been spotted where I am so I'll have to go look for it in the spring/summer.

Can't wait for you to get to the hairy woodpecker discussion!

Happy New Year.

Bosque Bill said...

This is one of the birds I've looked for many times specifically without success. I've visited many areas in NM's Jemez Mountains and up on Sandia Crest where they have been spotted regularly, but sporadically. No joy, so far, but I haven't given up.

Thanks for the article.

Beverly said...

Well, I have the feeling 2009 is going to be better on all counts...so perhaps it will include your finding the bird!

I just read that it is global warming that is causing so much beetle damage...and the removal of diseased trees by the timber cutters. What a shame, huh? Why is it we have to harvest in old-growth forests, anyway. Why can't they grow their own trees the way others grow corn?

That they replace wild forests with a monocultured woods of a single species seems unconscionable to me, too. Why can’t people think past their pockets?

I suppose I’m on a roll…that damn almost ex-president is trying to further muck things up before he leaves. Lordy I’ll be happy when we get a concerned citizen into the whitehouse!!!

Nice to see you again...