Long-Billed and Short-Billed Dowitchers

When I visited a duck pond at the Sonny Bono Salton Sea NWR Unit 1 it was covered with small brown birds. I just assumed they were least sandpipers and it didn't register until I got home and started looking at photos that there were two (or more) kinds of  birds mixed together, some that had substantially longer bills. 

Then when I looked up the longer billed birds I assumed they were long-billed dowitchers as opposed to short-billed dowitchers, but then later learned that the distinctions between the two are not great and they can be difficult to distinguish. 

According to Wikipedia, the two best field distinguishing marks are their flight calls.  Surfbirds has a detailed article breaking down the differences: 

Head shape:  lb - shallower forehead;  sb - steeper forehead

Lower back:  lb - deeply indented;        sb - less indented

Bill:              lb - straighter and longer; sb - curved down & shorter

Supercilium: lb - straighter & thinner;  sb - wider in front & flared

Well, that's tough. Here are some of my photos:

Bill slightly curved down, steep forehead - short-billed dowitcher. The next three photos are the same bird.

Looking at the front bird. Supercilium looks more straight. Bill looks straight. Perhaps a long-billed dowitcher. The next three photos are the same bird. 

Bill looks curved; steep forehead - short-billed dowitcher. 

The bird to the right looks like it has a straight V on the supercilium - long-billed dowitcher. 

Fun birds. I suspect there is a mixture of the two species.