Excerpts from Jim Conrad's
from the April 17, 2005 Newsletter issued from the Sierra Nevada foothills
somewhat east of Placerville, California, USA
AUDUBON'S WARBLERS AT DAWN
I'm still surprised to be seeing so few spring migrants. One reason may be that birds are most active in early morning, and that's just when it's so windy here at the canyon's edge. Wind tends to cut down on bird activity.
Probably the main reason, however, is that here we're not within a major bird-migration flyway as was the case when I was in Mississippi and western Kentucky. A map showing the Pacific, Central, Mississippi and Atlantic bird-migration flyways at www.pwrc.usgs.gov/BBL/homepage/bigbndc.htm indicates that here we're on the ragged west edge of the Pacific Flyway.
All through the day here I do hear a pretty, high- pitched, warbling call I associate with migration. In the East I'd unhesitatingly identify it as the call of the Yellow-rumped Warbler, but here the bird making the call has a yellow throat instead of the eastern Yellow-rumped's white throat, plus our bird bears a large white patch on its wing, which the eastern Yellow-rumped doesn't.
The deal is that here we have the western subspecies of the Yellow-rumped Warbler, and I'm accustomed to the eastern subspecies. When my old Peterson fieldguide was published in the 60s, it considered the two subspecies as distinct species, and referred to what we have here as the Audubon's Warbler, DENDROICA AUDUBONI. However, later it was recognized that where Audubon's Warbler meets the eastern subspecies -- then called the Myrtle Warbler - they hybridized producing intermediate individuals, so the two populations were lumped into the Yellow-rumped Warbler, DENDROICA CORONATA. You can see an "Audubon's Warbler" at www.pikespeakphoto.com/warbler.html.
On chilly mornings, how nice seeing this bird flying through stiff breezes from one sunlit Ponderosa Pine top to another, calling his pretty song. You can hear it yourself at www.naturesongs.com/yrwa2.wav.