Another Seabird ID Quiz

[Axel Hildebrandt]

I needed help with IDing this bird during a pelagic trip southeast of Cape Cod in August two years ago. I hope it is not too easy. :)

http://www.pbase.com/axelhi/image/84207742/original.jpg

[Julian Hough]

Axel,

The paler area behind the eye and just above and in front is good for Audubon's rather Manx, but the former is generally more uncommon than Manx in Mass. Manx usually have the dark area extending from before the eye, through the eye and then "hooking" up behind the eye. I do not see a MAnx-type facial pattern here, on what is really a superb shot by the way!

If this was taken on a rather longer range pelagic, I would expect Audubon's to be more of a probability. The browner upperparts are also better for Audubon's, but both species become browner through wear. In flight Audubon's have shorter wings and longer tails than Manx but on this shot, the feet are visible beyond the tail which might seem odd, but the tail looks very worn which might explain the visibility of the feet on this bird.

Do you have any other shots??

[Axel Hildebrandt]

Impressive start, Julian! If memory serves right this was south of Nantucket. I only have a very similar image of this bird.

[Ilija Dukovski]

Is the shape of the wings of any significance here? I've never seen Audubon's but as far as I remember
Manx have longer looking and not so round-ish at the ends.

[Dave Brown]

Hi All,

I've seen many many manx Shearwaters innewfoundland over the last 10 years.if I saw this bird during a Newfoundland seawatch I would have a heart palpitation and probably drop dead on the spot.This just looks wrong for Manx to me- face seems too white etc( See Julian's reasoning).I suspect if we could see the underside this would be even easier.

The more pertinent identification issue could be separating this from Little Shearwater,if we didn't know the location.Given that we do..I'd vote for Audubons.

Nice job Axel

Dave Brown

[John Chardine]

Audubon's Shearwater is a tropical species and feeds in warm sub-tropical and tropical waters. The warm waters of the Gulf Stream separate from the east coast of NA at about Cape Hatteras as you can see in this image from realclimate.org (my labels in white; red is warm water; an excellent web site BTW). The position of the Gulf Stream does not change that much summer and winter (see http://oceancurrents.rsmas.miami.edu/atlantic/gulf-stream_3.html), and remains roughly 500km off of Cape Cod at its closest (not sure how far you were out Axel). However, the edges of the Gulf Stream are variable and often warm water masses are pinched off the stream and travel northward (see warm water gyre in attached image), bringing tropical species with it. If these are big enough it could be all that an Audubon's Shearwater needs to maintain its warm-water association going north.

[Axel Hildebrandt]

Thanks, John! Interesting to see the map. This was a trip from Cape Cod to the gulf stream about 100 miles southeast of the cape but I'm pretty sure we saw this Audubon's Shearwater in the cold water south of Nantucket. I think it's called Nantucket Shoals. It was amazing to see the different species within a few miles when the water temperature went up from the lower 50s to the mid 70s.

[Julian Hough]

The facial pattern is a little off for Little (Macronesian) Shearwater - which, as of last fall has been recorded off Mass on the same pelagic trip to the gulf stream, so it should be considered.

Little are blacker (like Manx) above with often more of a pale white area around the eye, isolating it even further than this bird and they show a diffuse paler area on the trailing edge of the wing, some even showing as pale whitish tips to the greater covert.

This Audubons shows none of those features and I believe Little have bluish feet and the great shot of Axel's shows a bird with pinkish feet.