Tuesday, March 31, 2009

How did the Hermit Warbler get its name?

Thanks for the question, Jim D. in Delvan, WI.


Perhaps the reason relates to how it’s often easier to hear than see them, as Hermit Warblers typically forage individually high in the tree tops — hence, the common name that John Kirk Townsend first described when collecting this species in 1837 near Fort Vancouver (now Vancouver, WA).

Considered part of the Black-Throated Green “super species” — along with Black-throated Green (Dendroica virens), Golden-cheeked (D. chrysoparia), Black-Throated Grey (D. nigrescens) and Townsend’s (D. townsendi) warbler — the Hermit Warbler breeds in coniferous forests of the Coast, Cascade, and Sierra Nevada mountain ranges of southern Washington, Oregon, and central and northern California.

Where it occurs with Townsend’s Warbler within the s. Washington Cascade Mtns., Olympic Mtns., and central Oregon Cascade Mtns., Hermit Warbler may be losing populations as it is replaced and outcompeted by its first cousin. Studies by S. Rowher and C. Wood from 1994 to 1996 in this region indicate that 80 percent of adult Townsend’s and only 53 percent of adult Hermit paired and maintained their territories long enough to reproduce successfully. Other data relating to aggression behavior and hybrid zone analyses further supports Rohwer and Wood’s conclusions. Another reason for the reduced local populations of Hermit’s may be the result of reduced suitable breeding habitat in portions of its home range.

Nonetheless, in other portions of its range where Townsend’s Warbler does not breed, Hermit Warbler population densities appear to be stable, according to Breeding Bird Surveys (BBS) conducted in the last 30 years. However, it’s important note that BBS surveys are limited to routes where roads occur, so more comprehensive surveys of the Hermit’s total abundance do not exist. In addition, given the Hermit Warbler’s inherent small population worldwide and narrow geographic distribution, it is not considered abundant or common in most portions of its home breeding range.

Monday, March 16, 2009

Latest Warbler Quiz Answers

Below, you’ll see correct answers to recent quizzes that appear on the right side of this page (in order, from the most recent quiz to older ones):

Which "New World" wood-warbler species has the most extensive breeding area?

Answer: Yellow Warbler

Unlike Blackpoll that undertake a long migration (see 1/8/09 article), which wood-warbler has populations that do NOT migrate?

Answer: Common Yellowthroat

What behavior displayed by American Redstart is different than most other songbirds?

Answer: Some females sing

Which wood-warbler species spends the winter in large numbers in higher latitudes than any other wood-warbler?der members?

Answer: Yellow-rumped Warbler

Friday, March 6, 2009

Returning Wood-Warblers In The Bay Area

Birders are reporting the initial appearance of northbound migrating wood-warblers to the Bay Area this week.

Newly-arrived ORANGE-CROWNED WARBLERS are currently joining brave over-wintering populations, with Oak-Bay woodlands one of the best habitats to hear and seem them.

Note the annual date range of first-returning migrants for this species in Marin County (the initial county north of the Golden Gate Bridge) is 2/18 (earliest detection) through 3/16 (latest detection), according to Dave Shuford’s “The Marin County Breeding Bird Atlas.”

Soon, other nesting wood-warblers of the Bay Area shall also appear, with their identities and date range of arrivals in parentheses below:

- WILSON’S (3/10 – 4/8) (shown above)

- BLACK-THROATED GRAY (3/31- 4/27)

- YELLOW (4/8 – 4/23)

- MACGILLIVRAY’S (4/3 – 4/30)

For a comprehensive list of arrival dates for Marin County landbirds, feel free to visit my Web site (www.warblerwatch.com) where there’s a button that provides access to the Atlas’ chart (page 39).