Near the end of May, I was able to photograph two Dowitchers at Swan Lake. At the time I remember noticing that one bird seemed darker than the other, but I think I attributed it to different stages in their transition from winter to breeding plumage and did not really think much about it beyond that. Today while looking at them again, I realized that the darker one has white feather tips and minimal rusty margins, while the other lighter bird has more substantial rusty margins that go to the feather tips with much less white.
Note mostly black feathers with white tips. Little-to-no rusty colored side margins.
Note breeding plumage feathers with much more rusty colored sections, especially along the margin. No white feather tips.
These differences made me wonder if this is normal variation within Short-billed Dowitchers or if one of them (presumably the darker one) is a Long-billed Dowitcher. Any help would be appreciated.