The Carlisle Mosquito Online

Friday, January 19, 2007

Features

Biodiversity Corner Downy Woodpecker (Picoides pubescens)

(photo by Tom Brownrigg)
While walking around the edge of a cornfield at Great Brook Farm State Park, I noticed a Downy Woodpecker pecking at a cut-off corn stalk. This bird was a male, since it had a small patch of red at the back of its head. The bird would peck at the stalk for a while, and then move on to another. I could not tell what it was getting, but its behavior intrigued me. I later found a helpful reference (1): "A. Dawes DuBois says in his notes: 'I have seen a downy woodpecker industriously applying the percussion test to the dried stalks of the previous summer's horse weeds [probably Erigeron candensis], which grow to prodigious size in the creek bottoms near Springfield, Illinois. He went up each stalk, tapping it lightly, and frequently stopping to pierce the shell and extract a worm [insect larva] from the pith. I found that the weed stems he had visited were punctured and splintered in numerous places.'"

Downy Woodpecker is the smallest woodpecker in North America and is the woodpecker you are most likely to see in Carlisle. The less common Hairy Woodpecker (P. villosus) looks very similar but is about 50% larger, and its bill is much longer relative to the size of the head. During Carlisle's annual Christmas Bird Count, count totals for Downy have averaged about four times greater than for Hairy, and count numbers for the two species have increased or decreased together about half the time.

According to Gruson (2), the Downy's genus name Picoides derives from the Latin picus, meaning "woodpecker" and Greek eidos, "like or resembling." The species name pubescens is from the Latin meaning "coming into puberty." Gruson states: "To some, this species appears to be less hirsute than the Hairy Woodpecker. Downy is another suggestion that the species is less mature." The Hairy Woodpecker's species name villosus means "hairy or shaggy."

Both the Downy and Hairy have very long tongues that extend an inch or more beyond the end of the bill. The tip of the tongue is barbed and covered with sticky mucous, which allows the birds to extract larva of wood-boring beetles and other insects from deep holes. The Downy's diet is about 75 percent insects, mainly beetles, ants and caterpillars. Plant material includes seeds and fruits such as the berries of poison ivy and dogwood. Both species visit our feeders, and eat suet, sunflower seeds and sunflower hearts. Downys are reported to eat peanut butter, corn bread and doughnuts (3), but make sure the Carlisle black bear is not around if you try this.

In the fall, both sexes excavate fresh roost holes in a dead snag or limb for the winter. These holes are sometimes used for nesting in the spring. The entrance is nearly circular, and about one and a half inch in diameter (4). I found a possible nest hole in a broken top of a dead sugar maple that had blown down in our yard. The hole diameter, measured at eight locations, was 1.21 +/- 0.03 inches and the stump diameter at the hole was 5.73 inches. I did not open the stump to see if it had been used for nesting, since I thought the birds might still use it as a roost. One winter several years ago, a female Downy roosted in a bird nest box near our bird feeders. Bird nest boxes are used for roosting but are rarely used for nesting (4).

In early spring, you might hear a Downy Woodpecker drumming on a tree or other resonant object, including your house siding or gutter. Drumming is done by both sexes and is thought to mark breeding territories, and also announce the presence of a potential mate (3). If you find a dead snag on your property with woodpecker-sized holes, consider leaving it, if it poses no danger. Other native birds such as Black-capped Chickadees, Tufted Titmice and wrens often reuse woodpecker nest holes.

References

1. A.C. Bent, Life Histories of North American Woodpeckers, Dover Publications, New York, 1964. http://home.bluemarble.net/~pqn/ch11-20/downy.html

2. E. S. Gruson, Words for Birds, Quadrangle Books, New York, 1972.

3. J. K. Terres, The Audubon Society Encyclopedia of North American Birds, Wings Books, New York, 1991.

4. H. H. Harrison, Birds' Nests (Peterson Field Guides), Houghton Mifflin, Boston, 1975.


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