Posted by Don Roberson (63.174.196.30) on August 26, 2002 at 17:48:09:
Chandler (1998), in a paper that seems to be much-overlooked in North America, proposed new criteria for separating adult dowitchers on the relative length of wing and tail. He uses many color photographs to illustrate his points. The primary point that was new to me was the proposal that in all races of Short-billed Dowitcher the primaries project beyond the end of the tail (seen in good side views) whilst in Long-billed Dowitcher the tips of the primary projection falls short of the tip of the tail. Short-bills have longer wings than Long-bills, and their primaries extend 2-3 mm beyond the end of the tail; the folded wingtips of Long-billed usually fall 1 mm short of the tail tip or more, but some can be about equal in length to tail tip. Chandler states this mark has been mentioned by a few others, including Jaramillo & Henshaw (1995), but it is not often mentioned in discussions.
Chandler emphasizes that the character only works on adult birds with full wings. Because juvenal birds have wings that still may be growing, the character does not work on juvenal dowitchers; that's okay because juvenals are easily identified on other features (e.g., tertial pattern). On adults, care must be taken to assure that the bird is not in wing molt (typically Sep-Nov).
I have been trying this feature for several years in the field and I think it works rather well in general, although there are some ambiguous birds where the wings and tail seem about equal in length to me. This photo is a good test of this character. This is obviously an adult in body molt, but I do not believe that the bird is yet in wing molt. Accordingly, since the longest primary tip falls just short of the tip of the tail, this should be a Long-billed Dowitcher.
References cited:
Chandler, R. J. 1998. Dowitcher identification and ageing: a photographic review. Brit. Birds 91: 93-106.
Jaramillo, A., & B. Hensaw. Identification of breeding-plumaged Long- and Short-billed Dowitchers. Birding World 8: 221-228.