Monday, August 18, 2008

Vagrant Eastern Wood-Warblers in the West….

……and it’s the best time to see them.

September and October are often the best months to see eastern wood-warblers in coastal areas (such as northern California, including Point Reyes National Seashore in Marin County).

But you can also see them inland, especially within dense, tangled growth along rivers and creeks.

Which eastern wood-warbler species appears in this photo?

It was photographed by Martin Meyers in the Sacramento area on 10/1/04. (The answer appears at the bottom of this entry.)

According to one study published as “On the Occurrence of Eastern Wood Warblers in Western North America” (George Austin, Winter, 1971) in The Condor, 28 species of eastern wood-warblers have been detected in California. This study does not account for more recent published data.

Among the 28 species, the rarest to see is Cerulean, Prothonotary, Worm-eating, Golden-winged, Blue-winged, Prairie, Louisiana Waterthrush, and Mourning.

Other wood-warbler species that are often considered rare or vagrants in California have wintered in recent years, such as Black-and-White, Palm, Northern Waterthrush, and American Redstart*. At least five other species are believed to have wintered one or more times: Tennessee, Northern Parula, Chestnut-sided, Blackpoll, and Ovenbird.

As for where you can see vagrant eastern wood-warblers on the West Coast, I do not intend this entry to be a comprehensive tell-all summary. Instead, I’m featuring a well known “vagrant trap” -- Point Reyes National Seashore (PRNS) –- as one suggested destination that you may choose for your sleuthing effort. Within PRNS, checkout the Monterey Cypress groves that occur as “islands of green refuges” at the Outer Point amidst the dairy farms and chaparral. These groves represent wayside oases with dense vegetation providing food resources amidst otherwise inhospitable conditions — for eastern wood-warblers that, in most cases, have lost their way as they dispersed or migrated from breeding grounds.

Disoriented, these eastern wood-warbler individuals are often at the extreme western point of their post-breeding season movement. Many may even continue flying farther west, winging their way over the ocean with oblivion their unintended destination.

The lucky ones find regugia within eventual landfall, such as a group of seven islands called the Farallone Islands (27 miles west of San Francisco and 20 miles south of Point Reyes National Seashore's Outer Point). It’s another ideal venue where researchers observe eastern wood-warblers – with the tenancity of these lost survivors surely admirable. But, alas, the cruel penalty for their aimless perigrination often means an unfortunate early exit from our world – and the Outer Point and Farallones serve as “purgatory” waysides before fate interludes.

(* = Note an annual population of American Redstart nests in northwestern CA, I do not consider sightings of it on the West Coast to be absolute vagrant/accidental observations. Instead, it’s safer to consider sightings of this species in late summer/autumn are either West Coast or East Coast breeding individuals.)

(Chestnut-sided Warbler appears in the above photo that you can enlarge by clicking on it.)


Anonymous said...

Got any tips for finding *western* wood warblers in the eastern half of the country? That seems especially difficult.

Anonymous said...

Thanks. I didn't know this stuff.

Anonymous said...

When will you give the answers to the quiz questions?