Friday, September 29, 2017

Long-billed Dowitcher ID - What To Look For

Every shorebird season, birders are faced with the dilemma of separating Short-billed (SBDO) from Long-billed Dowitchers (LBDO). This post is not intended to list all of the nuances of how to tell them apart but I will share some of my own empirical observations.

Short-billed and Long-billed Dowitchers - Jamaica Bay Wildlife Refuge NYC
Let's start with the jiss (jizz). A classic Long-billed Dowitcher, is not that hard to pick out especially if you have one of those nicely fed female types. When I see an LBDO that stands out, I tend to think of an inflated football (American) or think Egg shape. Picture the higher part of the football as the back of the LBDO with tapered ends. In comparison to a Short-billed Dowitcher, one could easily spot this difference as the back of an SBDO is flatter. This physical feature also applies to the lower body as the undercarriage of a SBDO is straighter than that of a LBDO.

Juvenile Short-billed Dowitcher - Jamaica Bay Wildlife Refuge NYC
This shape feature should be used cautiously; especially, since this feature can be a bit more difficult to discern with an underfed Long-billed Dowitcher (LBDO) or a male LBDO in a a flock of fat Short-billed (SBDOs). Also, the posture of the subject bird in the field is very important not to be led down the wrong path. This is where you need to be aware of additional field marks to get closer to a conclusive ID. Some of the other useful features include, areas like - The neck: The neck of a Long-billed is thicker than a Short-billed, this is quite evident in the field if you have a side by side comparison.

Short-billed and Long-billed Dowitchers side by side - Jamaica Bay Wildlife Refuge NYC
The bill:  if carefully studied, the bill can offer excellent clues as to the ID of a Dowitcher sp. Take the bill of a  Short-billed Dowitcher - it is thicker, shorter and wider at the base. In comparison, a Long-billed Dowitcher shows a longer bill (quite evident in females) which is not as thick as a Short-billed Dowitcher. The tip of a Short-billed Dowitcher's (SBDO) bill shows a distinct kink - a feature that looks like the bird caught its bill in a closing door. On a Long-billed Dowitcher (LBDO), this is not so evident and aids in the longer, thinner looking bill tip.

Long-billed Dowitcher (C) among Short-billed Dowitchers - Jamaica Bay Wildlife Refuge NYC
This leads me into an ID feature that I have worked on in the field when trying to separate those tough small male Long-billed Dowitchers from big female Short-billed Dowitchers. At the base of a Long-billed Dowitcher, there is a pinched look just where the base of the culmen meets the face. This gives the impression of a steeper incline where the bill meets the forehead. In comparison, the base of the culmen on Short-billed Dowitcher has a smoother less inclined meeting with the forehead. This feature is one that I personally have focused on when analyzing Short-billed from Long-billed and I have yet to encounter where it has troubled me. Even on single species, this is a quick feature thrown in with other field marks that I am able to eliminate any suspected LBDO in a flock of Short-billed Dowitchers.

Short-billed Dowitcher (Hendersoni subspecies) - Cupsogue LI NY.
This brings us to plumage and I will not get into the differences in the upper feature of Short-billed Dowitchers vs Long-billed Dowitchers because I do not have enough sample images to share which could clearly point out the color differences in feather edges. Here in NYC, we get most Long-billed Dowitchers when breeding plumage is showing some wear and so if we are looking at color, we turn to the underparts. On an LBDO, the underpart shows a more brick red color while on an SBDO, the color is more orange like. Keep in mind that in both cases, feather wear will result in various shades that could be troublesome. Long-billed Dowitchers, underpart color extends to the undertail and only the prairie subspecies Hendersoni, shows this. This is also another useful clue when analyzing a flock.

Short-billed Dowitcher (Hendersoni subspecies) - Cupsogue LI NY.
I have included a few images which I hope will aid in differentiating Short-billed Dowitchers from Long-billed Dowitchers. The next step is to get out into the field and look at all your Dowitchers, carefully.

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