North American Birds

VOLUME 70 NO2 2018

A Quarterly Journal of Ornithological Record Published by the American Birding Association. The mission of the journal is to provide a complete overview of the changing panorama of our continent’s birdlife.

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145 V O L U M E 7 0 ( 2 0 1 8 ) • N U M B E R 2 PRESUMED COLIMA x VIRGINIA'S WARBLER HYBRIDS IN TEXAS Canyon (7,000 feet elevation) discovered a singing male warbler that appeared to ex- hibit plumage characteristics and a song pat - tern consistent with Colima Warbler. After extended observations and documentation with photographs and song recordings, the bird was identified as a definite Colima War- bler, representing the first summer record of the species in the United States away from the Chisos Mountains (Bryan and Karges 2001). This individual stayed on a well-defined ter- ritory for almost two months and sonograms of the recordings confirmed that the song was typical of a Colima Warbler; however, actual breeding was not confirmed. This bird was found well below the upper elevations of the range in a deep canyon and on adja- cent alluvial slopes with habitat comprised primarily of pinyon-juniper-oak woodlands with extensive stands of Silverleaf Oak and scattered Ponderosa Pine glades. Plumage Characteristics & Morphological Data The Virginia's Warbler is usually character- ized as a small-to-medium-sized warbler, generally gray with a mostly concealed rusty crown patch, white eye-ring, yellow on the central portions of the breast, and yellow upper and under tail coverts. The Colima Warbler is characterized as a medium-sized warbler, generally brownish in color with a somewhat more conspicuous rusty crown patch, whitish eye-ring, no yellow on the central portions of the breast, brown back and flanks, and more golden-yellow upper and under tail coverts. Virginia's Warblers are normally described as being much small- er than Colima Warblers, averaging 10-20% smaller based on published morphological data (Benson and Wauer 2013). As surveys continued in the Davis Moun - tains into the early 2000s, an emphasis was placed on locating additional Colima War- blers to determine the species' population status. It was during these efforts that several singing males were encountered that initially appeared superficially similar to Colima Warbler but which exhibited combinations of plumage characteristics and song patterns that were inconsistent with Colima or Vir- ginia's warblers. These individuals appeared Figure 6 • Presumed male hybrid in Silverleaf Oak in Madera Canyon on 8 May 2005, with reduced brown tones in the body plumage but lacking the classic gray of a Virginia's. Photo by © Mark W. Lockwood. Figure 7 • Presumed adult male hybrid in fresh basic plum- age, captured and banded (2070-64858) on 3 September 2016 in upper Limpia Canyon. Note the all-brown coloration of this bird, which had measurements mostly consistent with Colima Warbler. Photo by © Kelly B. Bryan.

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