Shearwater

[simonthetanner]

These are older shots from a pelagic trip I did a few years back, off the Oregon coast in September. It is a shearwater, either Sooty or Short-Tailed; the former is abundant in the area, but our group had at least 2 SRTS on that trip. I'm submitting these here for ID help by others with more experience differentiating shearwater species.

Image #1:


What catches my eye about this bird is the steeply-slated forehead, rounded head, and short, stocky neck. 

I don't know what to make of the bill: Seems shorter and finer than that of most of the other SOSH I photographed that day, but I'm not sure it's short enough to support SRTS.

Underwing coverts are a bit hard for me to evaluate, as the lighting is very dull. Sibley's notes that SRTS should show generally darker and more uniform coverts, and Howell & Zufelt emphasize the lack of contrast between primaries and coverts. This bird seems quite muted and generally consistent with SRTS, but I'm not confident enough with shearwaters to make an ID based on this.

I don't see a pale chin on this individual

Image #2:

Taken almost 40 minutes later at the same general location. I'm not sure this shot is IDable, but it shows many similar features in body-shape.


Any thoughts are welcome. I'm particularly interested in *how* to systematically work through IDing these. Thanks!
 

[Connor Cochrane]

This is a difficult bird. My dad has a boat and we head out around the farralons (Islands 25 miles off of SF). And have yet to find a short tailed mixed in with any sootys, but I’ll give it a try. Your first bird looks pretty good for Short-tailed. It has a very short, small beak, and head shape, rounded, strep forehead. I have no expirence, but it logs pretty goods for SRTS. My only problem is the middle of the underwing seems fairly gray, but that could just be lighting. I don’t feel confident in the second bird. It’s more intermediate in my opinion.