Bird of the Month: Fork-tailed Storm Petrel
By Andy McCormick
PC: John James Audubon (Fork-tailed Storm Petrel)
Scientific Name: Oceanodroma furcata
Length 8.75 in
Wingspan 19 in
Weight 2.1 oz
AOU Band code FTSP
The cascading song of the Canyon Wren descends from cliffs and canyon walls, and is surely not forgotten once heard. It is most often heard in spring, but there are times when a mated pair will sing spontaneously at other times of year. It is a bird of the west and is found from southern British Columbia to Mexico. In Washington, the Canyon Wren resides along the eastern slope of the Cascade Range and in canyons farther east.
It is in the genus Catherpes, from the Greek kathero, to creep down, referencing the bird’s habit of creeping down canyon walls. The species name mexicanus, Latin for Mexico, reflects the region where it was discovered (Holloway). There are more than 30 species of wrens in Mexico, which is the center of diversity for wrens (Floyd, in Alderfer).
Adapted for Foraging on Steep Canyon Walls
The physical structure of the Canyon Wren has evolved to improve its ability to forage deep into crevices in the canyon walls. It has the longest bill of any wren and its spinal structure allows it to forage directly forward. Its cranium is flattened and, because the tarsi are short, lowering its center of gravity, its height at the shoulders is also lowered. This adaptation reduces its overall profile enabling the bird to probe into narrow spaces (Jones and Dieni).
The Canyon Wren, “Hops on rocks while foraging, examining crevices for spiders and insects…. Moves rapidly on and under rocks and into crevices. Often spreads its legs while probing, so that its breast and center of gravity are low to the ground ….Extends neck forward with bill as close to the ground as possible, and parallel to the ground. Clings to and climbs sloping or vertical rock and hops forward in small jumps” (Jones and Dieni).
It spends most of the year in arid country, but it will find places where there is moisture. A small cascade or water drip will provide cooler temperatures and habitat for spiders and insects on which it feeds. It may be entirely insectivorous.
Canyon Wrens Couple Up
Pairs of Canyon Wrens bond at least for a year and some for longer. Both sexes build the nest with a foundation of twigs, grass, and bark chips usually covered with fine grass, moss, and spider webs or animal hair. Common nest sites include crevices in a rocky cliff, in rock piles, or on a ledge. The nest most often has five reddish-dotted, white eggs. Incubation by the female lasts about two weeks. Both parents feed the nestlings, which are ready to leave the nest in another two weeks (Kaufman).
A Homebody
The Canyon Wren is a year-round resident, but it sometimes migrates to lower altitudes and possibly to denser habitats in winter. There are no conservation measures in place and the Canyon Wren is considered common and well-distributed in its range (Jones and Dieni). Study of the Canyon Wren is very difficult because of the terrain in which it lives. There appears to be some decline in population, but little more is known and current data are not reliable. Accounts indicate that more study is needed.