Sooty/Short-tailed Shearwater Side-by-side ID The Background I took a Cordell Banks/Bodega Canyon pelagic trip with Shearwater Journeys in late-November 1998 while collecting video and slides for the virtual tour of Northern California. One slide I shot was particularly interesting since it showed two dark shearwaters wing-tip to wing-tip. Close examination of the slide reveals that there are 2 different shearwater species. Both birds have dark bills ruling out Flesh-footed Shearwater and suggesting Short-tailed and/or Sooty Shearwaters. What makes the slide particularly interesting is that the underwing pattern is not readily apparent on either bird due to the perspective. Underwing pattern provides the most distinctive marks in separating these two species. Without underwing pattern one has to rely more on subtler marks. The slide is represented below as 3 images, one image with both birds and close-ups of each individual bird. I posted a query to the ID-FRONTIERS list on October 28, 2000 soliciting feedback from people about the ID of these two birds. The resulting comments are presented below. The Images Both Shearwaters Left Shearwater Right Shearwater Equipment: Canon A2e EF 300mm f/4.0L Fuji Provia ISO 100 My ID-FRONTIERS Query I'm working on a virtual tour/birding break for Northern California. One of the destinations is Cordell Bank which I visited in late-November a couple years back. I have a 35mm slide of 2 side-by-side dark-billed dark shearwaters that I'd like to use in the tour. I like the shot because it doesn't give a great look at either bird's underwing so you're forced to look at features of head shape, bill length, overall size and what plumage markings can be made out. I'd like to get a sense of how identifiable the birds are to decide whether I should scrap the shot for the tour and replace it with something that is less controversial. I'd appreciate any feedback people have on the identity of the shearwaters in the following images (all from the same slide). I'll post a summary back to the list or to a web page. (I then dyslexically mis-labelled the links to the 2 close-up, swapping left and right.) People's Comments Send additional comments to crockett@greatblue.com Simon Perkins from Lincoln, Massachusetts Wow. You picked a real tough one this time. I'm not sure the birds are definitively identifiable by these images. If you think they're both the same species then we're really in trouble, because if you held a gun to my head and asked me for an ID, I'd probably have to say that I thought they were two species. The one with the wings up seems to show a pale throat, steep forehead, shortish bill, and relatively limited white on the underwing, while the other seems to have a relatively darker throat, flatter forehead, and longish bill. In other words, #1 (wings up) looks more like STSH, and # 2 (wings level), SOSH. Unfortunately, the foreshortened angle is not especially helpfull for the profile traits, such as bill length, forehead shape, and general body/wing proportions; and underwing pattern is not clear enough. That's about as far as I can go. I know it's not much, but I hope it helps. If nothing else, it should generate plenty of discussion. (-: Angus Wilson I think all three shots are readily identifiable as Sooty (or possibly Short-tailed) Shearwater. Enough of the flanks and vent region is visible to eliminate Black-vented Shearwater. The flight style, bill shape etc. is obviously wrong for any of the dark Pterodroma (e.g. Murphy's Petrel). Without views of the underwing coverts, I'd be uncomfortable in trying to separate between Short-tailed and Sooty, although the fact that there is a hint of silvery white visible in each larger images even at this suboptimal angle strongly suggests Sooty to me. Hope this helps and I look forward to seeing comments from others. Kevin McKereghan Short-tailed on the left, Sooty on the right. Or so I beleive. I don't think the slide is unfair, or inconclusive, there is enough there to make the call, but it might be a wee bit painful if you're not from No. Cal though. Gavin Edmondstone from Oakville, Ontario Right: Short-tailed Shearwater Left: Sooty Shearwater (We seldom see those birds on Lake Ontario but we did have a Northern Gannet last weekend) Gary W. Potter Did you label the two individuals wrong. The one you labeled left is on the right on my screen. It looks to me like a Sooty Shearwater, with larger bill and flatter forehead. The other which is on the left of my screen, but you labeled right on the individual picture looks like a Short-tailed Shearwater. It's smaller, has a slender bill and high forehead. I hope this helps! Matt Sharp from Philadelphia, Pennsylvania I am by no means an expert on Pacific shearwaters and have never seen Short-tailed, but I think the comparison is awesome and shows the subtle differences in stucture and pattern of light and dark on the head/face very well. So well in fact that I wouldn't suspect there to be much controversy on the ID. ... Lisa Hug I guess the shearwater on the left is a Short-tailed and the one on the right is a Sooty. I've seen thousands of both off Australia and California and find them truly difficult. The left bird has the small head, obviously round forehead with a slim bill. There is a hint of white on the chin. The underwing pattern that is visible suggests a uniform pale gray with a neat narrow dark leading edge. Short-tailed underwings seem to have that distinctive look of a uniform color with a neat narrow black outline. The right bird by contrast has a large head and shoulders. The forehead is reasonably flat. The bill is big, thick, and the tubes are more obvious. I'm sure these are the features you want people to see. And they are surprisingly obvious in these photos. My only objection is that it makes these 2 look too easy to tell apart. It's just not like that in the field (or maybe it is and I'm just a little slow). Anyway, I vote to include the photos because it does make people see these differences and think about them and then try to apply them in the field. Phil Pickering I don't see anything controversial here. Left bird shows most of the classic marks for Short-tailed - thin, proportionately short bill high, steeply-angled forehead and proportionately small head thin body and narrow wings accentuating a long-winged look pale chin patch underwing relatively uniform silvery gray-brown only thing you can't judge is the extension of the feet beyond the tail. The right bird (Sooty) looks large-headed, large-billed, chunky, has a relatively flat crown and low forehead, and enough of the left underwing is visible to show the typical contrasting white area mainly on the secondary coverts. Great shot - this one should definitely be in a field guide! Stephen J. Davies from San Francisco, California Nice photo. The bird on the left looks good for Short-tailed Shearwater - the small, short bill (compared to the bird on the right), the white feathering on the chin and the dusky underwing identify it as such. The bird on the right looks more like a Sooty - larger overall size than bird on left, larger and longer bill and hint of purer white on the underwing suggest Sooty. I'd be interested to hear what others have to say SGMlod I took a look at the shearwater photo. On my computer, which does fairly well with such things, the critical bill shape/ forehead shape is difficult to make out clearly. The bird on the left looks smaller billed and steeper foreheaded, so I would go with Short-tailed on the left and Sooty on the right. However, I can not be certain, just because the dark edges of the bird blend in a bit too much with the dark water, making the contours difficult to judge. Greg Gillson Excellent views of Short-tailed and Sooty Shearwater. You might like to look at "Identification of dark-bellied shearwaters". Glenn A dEntremont from Massachusetts This may be a little late, but I thought I would comment. I have limited (one trip) experience on the west coast pelagics. It appears that the left bird might be a Short-tailed Shearwater while the right bird is a Sooty. The forehead on the right bird appears more abrupt and the bill appears thinner than the bird on the right. The throat and/or chin area is much paler on the left bird. The neck of the right bird appears thicker and the bird a bit more robust than the left bird. The pale markings on the chest of the left bird might be of little use, but I think still points toward Short-tailed.