Central Park Golf Course
California City, Kern County
25 September 1999
The following is based on notes taken while watching the bird:
An obvious Oporornis similar to MacGillivray's Warbler but with a yellowish wash to the throat and heavy black spotting along the lower edge of the hood. It superficially resembled an Orange-crowned Warbler, but with sturdy pink legs, and a larger, more rounded head, and thicker paler, blunter bill.
The narrow eye-crescents were whitish, similar to MacGillivray's Warbler, but the lower crescent was longer resulting in a more complete eye-ring effect. The upper crescent wrapped more behind the eye, but stopped forward of the top of the eye.
The upperparts were uniformly olive with a yellow spot visible along the marginal coverts near the alula.
The underparts were bright yellow except for the lower border to the hood, which was the same dingy-olive color as the back. This was heavily stippled with black only along the lower border. The olive became paler toward the throat and blended with a pale yellow wash there. The sides and flanks were also washed with olive.
The yellow undertail coverts were very long and pointed, almost reaching the tip of the tail. The tail was olive above and gray below. It twitched its tail quite a bit similar to MacGillivray's Warbler. In my experience, Mourning Warblers usually have less active tail-movements than this bird.
The chip-note was heard several times. It was a hollow (almost two-parted) "tsick" with the quality of Bewick's Wren. It differed from the thicker more solid call-note of MacGillivray's, and sounded much like Mourning Warblers I have heard in the past.
Jon Dunn identified this bird as an immature male. It is the only plumage which shows an apron of black spots along the lower border of the hood. MacGillivray's has no such pattern. The yellow wash to the throat, the very long undertail coverts and especially the call-note confirm the identification of this bird as Mourning Warbler. The face pattern was equivocal, but probably within the range of both species.
That night Gary Rosenberg showed excellent video footage of this bird. John Wilson and others attempted photography while I was watching the bird.