June 2000 Mystery Birds

Thank you all for the intriguing discussion.

The birds are a Chipping Sparrow and a Warbling Vireo. Unlike most other Spizella sparrows, the Chipping Sparrow routinely migrates in juvenal plumage. Such birds are seen around the San Francisco Bay area in good numbers during August and early September. Note the pink bill which is normal for juvenal and most basic plumaged individuals. The dark line extending from the eye to the bill is a key character separating Chipping Sparrow from Clay-colored or Brewer's sparrows and appears to be valid in all plumages.

Keeping with the theme of dark lines from the eye to the bill, this unusual Warbling Vireo was photographed 5 September 1982 at the Point Reyes Lighthouse. This date is much too early for Philadelphia Vireo to be migrating. The original photograph shows a very gray bird with no yellow on the throat or breast. I agree that overexposure on the computer image makes this feature somewhat ambiguous. Most Warbling Vireos have a more open facial expression because the lore stripe is usually incomplete or very faint. But occasionally Warbling Vireos can show a complete dark lore stripe as in this individual. One feature worth noting is that the lore mark on a Philadelphia Vireo is shaped more like a wedge than an even stripe. It is widest at the eye, and narrows down to a point towards the bill. This Warbling Vireo has its lore stripe thickest at the bill and slightly narrower at the eye, a reversal of the usual Philadelphia Vireo pattern. Also some Philadelphia Vireos are reported to have incomplete or obsolete lore markings, although I have never seen such a bird myself.

The original images are below. To view public comments or join the fray by adding your opinion, click here. Have fun!

Photos © Albert Ghiorso
All rights reserved.

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