April 98 Mystery Birds

As expected, the first sparrow generated to most divergent opinions and the most interesting discussion. In this case I saw the bird myself and was involved in the controversy surrounding its identification. Alan Hopkins found this bird and originally thought it was probably Brewer's but I talked him out of it thinking it was probably a Clay-colored. Several people saw the bird the next day in the same place after it had been reported as a Clay-colored on our local hotline. Either species is a rarity in San Francisco, but Brewer's is actually slightly rarer than Clay-colored in the city. Both are much more likely to be found in the fall than in spring.

Alan's photos were shown at a gathering of serious birders in San Francisco but there was no consensus among the assembled experts. I was still leaning toward Clay-colored while most people seemed to favor Brewer's. Eventually I had an opportunity to show the slides to Peter Pyle, coauthor with Steve Howell of the major paper on Spizella identification (Birding 28:374-387, 1996) who confirmed the identification as Clay-colored much to my relief.

The bird did show a pale median line on the crown, more prominent on the nape. This pale line was streaked lightly throughout, but still reasonably well defined. When Brewer's show a median line, it is usually confined to the forehead. The eyering of Brewer's is usually more distinct than on our bird. Peter Pyle mentioned to me that Clay-colored typically has the eyering broken and less prominent above the eye than below. In that respect our bird better fits Clay-colored. Contributors to our comment page mentioned the unstreaked gray collar and the mustachial stripe widening behind the eye which are also indicative of Clay-colored. I believe the main reason the identification was not more obvious is because of the dull gray supercilium which is typical of Brewer's but Clay-colored Sparrows can be quite dull and this bird is an example of that.

As this bird seemed to show somewhat intermediate characters, the possibility of "Timberline" Sparrow (S. b. taverneri) was raised. This is a poorly known race of Brewer's Sparrow which gained prominence when it was listed as a full species in the world checklist by Sibley and Monroe. Field identification of this form is problematic and the interested reader is referred to the paper by Pyle and Howell mentioned above. I think a "Timberline" sparrow should show more streaking on the gray nape than on this bird. The possibility of a hybrid Clay-colored x Brewer's is also interesting and worthy of consideration but it would be hard to prove without measurements.

Lastly, Chipping Sparrow is eliminated by the pale lores and strong malar pattern. I am quite sure this was a dull Clay-colored.

The opinions on the second sparrow were unanimous that it was the "large-billed" subspecies of the Savannah Sparrow (Passerculus sandwichensis rostratus). This should have been easy as photographs of this race contributed by Dan Singer are in the photo gallery here.

The original quiz page is below.

Mystery sparrow Mystery sparrow
Alan Hopkins photographed this controversial sparrow in San Francisco in May 1996. Click on the image to view full size.   Don DesJardin contributed this excellent sparrow photo taken near Ventura in December 1993. Click on the image to view full size.

What do you think these birds are?  Please click here to view comments or add your own.  Thanks.