Short-tailed Shearwater (Puffinus tenuirostris)

Taxonomy

Closely related to Sooty Shearwater.

Identification

Separation from Sooty Shearwater relatively difficult, especially on lone birds. When seen together Short-tailed Shearwater looks smaller headed and longer tailed than Sooty Shearwater. As Chris Corben warns, reliance on size and jizz can be complicated by individual size variation (Corben, 1999). The bill is smaller and less stout than in Sooty Shearwater. This is most obvious if the two species are seen together on the water. On the whole, Short-tailed Shearwaters have faster, neater wing beats and tends not to arch so high off the water. Obviously these features are highly dependent on wind conditions and are thus useful only in mixed company.

The underwing pattern is generally thought to be the most definitive feature, especially in the hand. In flight, details of the underwing can be very difficult to see and are certainly affected by the state of wear. In Sooty Shearwater, the palest part of the underwing are the primary coverts, which contain extensive areas of pure white sharply contrasting with dark streaks. This pale area tapers inwards towards the body, up the middle of the innerwing and is offset by the dark subhumeral or axillar feathers. In Short-tailed Shearwaters, the center of the underwing may be uniform grey/brown or have the white restricted to the middle of the secondary underwing coverts.


Fig. 1. Hundreds of thousands of Short-tailed Shearwaters (Puffinus tenuirostris) and Sooty Shearwaters (Puffinus griseus) pass through the narrow breaks in the central and eastern Aleutians to reach their feeding and molting grounds in the Bering Sea. Photograph copyright of Angus Wilson©.

Separation from Sooty Shearwater is perhaps easiest in fresh plumage. In the northern hemisphere, this is attained once birds have reached the Aleutian Islands and Bering Sea. In fresh plumage appear very dark headed, so much so that the eye is almost invisible.
 

Where and When

Spends the non-breeding season (boreal summer) in the north Pacific and Bering Sea. Postbreeding adults take approximately 6 weeks to reach the Bering Sea from Australia. The first individuals reach the Bering Sea at the end of April with the majority arriving in May and June. Common to 71 deg N in the Chuckchi Sea or even beyond. During the summer main food items are euphausiids (70% of diet) turning to large hyperiid amphipods during the fall. Diet is supplemented with squid and small fish. These are obtained by plunge-diving and surface seizing.

Some adults begin to turn south in late August, but species still very abundant in the Bering Sea until mid-August. Most birds leave the Bering Sea during September and October but a few individuals stay until as late as mid-November.
 

Photographs on the web

Amazing detail of upperparts and head Taken by Tony Palliser off Wollongong NSW in October.
 

Literature

Chris Corben (1997) [BIRDWG01] Shearwater ID Problem. Posting to NBHC Id-Frontiers, on 18 Dec 1997.

Kerry, K.R., Horne, R.S.C. and Dorward, D.F. (1983) Records of the Short-tailed Shearwater, Puffinus tenuirostris in Antarctic waters. Emu 83(1): p35-37



Copyright © 2002 All rights reserved. Angus Wilson

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