ML202297471

Age

Not specified

Sex

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Observation details

Okay, so here goes. My reason for observing the dowitchers here closely was to see if I could derive heuristics for separating out non-breeding long-billed dowitchers from short-billed dowitchers and finding characteristics unique to each species. Long-billed dowitchers have been known to forage in this pond along with short-billed dowitchers, so it gives me an excellent opportunity to compare and contrast birds at the same time up close. These are my findings: Hypothesis: the small sparsely-knit group of dowitchers that were foraging in deeper water (~3 inches, enough to reach their bellies) are long-billed and the much larger group of dowitchers foraging in unsubmerged or only submerged mud were short-billed. 1. Do they have longer bills? Yes. On average, the bills of the deeper water group (n=8) were around 10-15% longer than the bills of the shallow water group (n=9) with only very slight overlap of the longest-billed individuals of the shallow water group just barely being the same length as the shortest individual of the deeper water group. 2. Plumage differences. While almost identical in plumage, some differences do start to stand out. The deeper water group tended to have more "textured" wing and back feathers, specifically darker on the center and lighter toward the edges while the shallow water group tended to have more "flat" wing and back feathers, but this effect was rather minor. Some of the shallow water had more speckled or streaked throat and breast, but not all of them. The deeper water group had all plain gray-brown throats and breast. 3. Physical differences. Other than bill length, there is some difference to bill shape - the deeper water group had bills that seemed to go more or less straight into their face, while most of the shallow water group had bills that tended to flange out just a little bit at the base, giving a feel that the bill was slightly separated from the rest of the face. As others have mentioned, the "hunched" appearance is noted, although beware - this may also somewhat be affected by the differences in foraging behaviors of the two groups, as on occasion I did see a more hunched look out of definite SBDO individuals. The deeper water group also had a more plump appearance overall, especially if you could view individuals from both groups next to each other. 4. Feather wear. During migration, LBDO can be separated from SBDO due to the fact that LBDO completes its wing molt a month earlier than SBDO. At this point in early January, both have completely molted, so we cannot look for an incomplete molt, but what we can do is look at how much wear is on the feathers of each individual. From what I noticed, the deeper water group tended to have more worn wing coverts and primaries than the shallow water group, most notably, that in the deep water group most individuals had completely lost the white edges on their wing coverts, whereas most individuals in the shallow water group had near complete white edges. 5. Behavior. The manner that the two sets were foraging tended to be different, with the deeper water group moving more slowly, spending more time on the same spot with their head down, tended to be less social and stayed fairly spread apart, while the shallow water group were constantly on the move while foraging, calling to each other, flocking together and foraging together. Some of this may be due to the fact that the deeper water group is in deeper water, but also I noticed the deeper water group tended to ignore the calls of the others and stay where they were while the others flew off all at once together. There were very few cases the two groups mixed while foraging. 6. Calls. This is a rather weak point, as I heard only one or two "keek" calls and the deeper water group stayed pretty much silent while I was recording them. The shallow water group were calling on many occasions, very much a chattery SBDO call as you might expect. Update 12/27/2022, I updated the count based on a photo that shows at least 12 identifiable LBDO together in flight.

Technical information

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