Greg Gillson has written an excellent article on telling Short-billed from Long-billed Dowitchers. http://thebirdguide.com/identification/dowitchers/dowitchers.htm But I'm still not doing well. The photos I've taken at Baskett Slough are not the greatest, which is my excuse for not being able to figure out who is what. I'll try to do better on my next trip to the feed store, via Baskett Slough. Here is the pertinent part (for me, this time of year, in this area) of Greg's article:
"A fall adult with little or no color on the underparts, but retaining extensive thick, solid alternate breast markings is almost certainly a Short-billed, while a fall adult retaining smooth reddish color throughout the underparts including the belly, but with very thin-looking, worn breast markings is almost certainly a Long-billed.
Juveniles (young birds in their first set of feathers after the downy plumage) are the easiest dowitchers to tell apart. The plumage is fresh and new with crisp, bright, colorful edges--very unlike the worn and faded adult fall dress.
Juvenile Short-billeds arrive in early August and migrate through until the end of September. Juvenile Long-billeds arrive in early September and remain in this plumage into November. They then molt sequentially into basic plumage. The tertials are among the last feathers to molt.
Juvenile Short-billed Dowitchers are very bright and highly colored. The upper breast is bright buff with spots, fading to white on the belly. The scapulars and tertials are widely fringed and patterned with reddish [see Figure 3]. The coverts are barred and fringed with buff.
Long-billed Dowitcher juveniles are rather plain. The scapulars have cinnamon margins, but the coverts and tertials have thin buff margins. The breast is buff and gray with little spotting, which fades into a white belly."
Some good photos of Dowitchers with identities revealed (or not and why not) are here: http://thebirdguide.com/identification/dowitchers/dowitcher_intro.htm
Okay, my bad photos at the top were taken Aug. 3, 2011. My bad photo below, Aug. 8. Opinions welcome. I'm going to guess that the bird in the last photo above with the very long bill is a female Long-billed Dowitcher... because the female Longbills have the longest bills... and birds inland should be Long-billed. I'll try to get better photos. I was going for art, not identification.