Birding Alaska

Short-tailed Shearwater Puffinus tenuirostris, Bering Sea, 25 September 2009.

Pretty slow birding from the NOAA Ship Miller Freeman today.  The ship’s mission during this cruise is to retrieve and replace oceanographic moorings in the Bering Sea and conduct physical oceanographic studies.  We left Dutch Harbor two days ago and we’ll be out until October 13th.  I’m riding along as a seabird observer and I spent some time today observing Short-tailed Shearwaters while the crew worked on a couple oceanographic moorings.  Here are a few photos to improve the previous post on shearwater ID from April. Coincidentally, these recent photos were taken in the exact spot as those I took in April.

Short-tailed Albatross Phoebastria albatrus, Northern Fulmar Fulmarus glacialis and a few Short-tailed Shearwaters Puffinus tenuirostris, Bering Sea, on the shelf-break about 140 miles west of St. Matthew Island, 3 August 2009.

Two immature Short-tailed Albatross spent much of the day around the ship today as the ship conducted pollock surveys. One of the birds is starting to show some white feathers coming in on the throat and around the eyes and its plumage is a bit lighter brown than the other albatross which showed uniformly dark brown plumage with no white feathering. At times both albatross sat on the water and did a courtship-like display, gently wagging their bills bag and forth, sometimes touching each other. We were surprised to see to young immatures engaged in this behavior, but I guess it has to start sometime. Last night while in Russian waters a dark juvenile and an adult Short-tailed Albatross made brief fly-bys of the ship.

Short-tailed Shearwater Puffinus tenuirostris, western Bering Sea, 27 July 2009.

Twenty foot seas are gone–today the sea was a mirror.  The feather detail of this molting Short-tailed Shearwater is clearer in the reflection than it is on the bird!

The ship moved into Bristol Bay a few days ago where the highlight has been an early Sabine’s Gull on 28 April.  The bird numbers dropped dramatically after we left the deep waters west of Bering Canyon and entered the shallower waters of Bristol Bay.  However, the last two days transiting deep water (26-27 April) were great and produced 2 more Mottled Petrels and 2 Leach’s Storm-Petrels–both of which are exclusively found over deep water.  We also recorded 4 Red-legged Kittiwakes on this transit.  There have been nice numbers of Short-tailed Shearwaters, both over deep water and in the shallower waters of Bristol Bay.  Many of the shearwaters have been occurring in tight flocks of 30-50.  Watching Short-tailed Shearwaters maneuver in a 30 knot wind is about as good as it gets!

Short-tailed Shearwaters Puffinus tenuirostris in Bristol Bay, 29 April 2009.

When compared to the similar Sooty Shearwater, note the steep forehead and shorter, thinner bill of the Short-tailed.  Contrary to popular belief the “underwing flash” of a Sooty is not a reliable field mark for separating the two species.  Short-tailed Shearwaters can show a flashy underwing (see top photo), especially when seen in bright light as these birds were.  On a Sooty Shearwater, however, the brightest part of the underwing is the underwing covert panel and these bright underwing coverts contrast with the bird’s darker flight feathers.  The underwing of a Short-tailed Shearwater is more uniform and can range in coloration from dark to light.  When Short-tailed Shearwaters show a pale underwing it is a uniformly pale, or “flashy,” underwing and the flight feathers, especially the primaries, are also pale.  In the top photo of the two Short-tailed Shearwaters note how the paleness of the underwing extends onto the primaries, which don’t contrast with the under-primary coverts as they would in a Sooty.   Structural clues and flight styles are also extremely important, especially when the two species are seen together.

Click here for an excellent article (with excellent photos) by Greg Gillson, published in Birding magazine, which details the seperation of these two species.