Contents |   Seabirds   |   Colonies   |  Other Sea Life   |   Take a Trip   |   Trip Reports   |   Sources  |    TOP


New England Seabirds

 Wilson's Storm-petrel  Dave Jones

Seabirds

Shearwaters Index
Great Shearwater
Sooty Shearwater
Cory's Shearwater
Manx Shearwater
Audubon's Shearwater
Little Shearwater

Comments to webmaster

 

Shearwaters

 

 

Cory’s Shearwater Complex

Cory's Shearwater
Calonectris diomedea borealis

Scopoli Shearwater
Calonectris d. diomedea

Cape Verde Shearwater
Calonectris edwardsii



Cory's Shearwater Scott Surner

Cory’s Shearwater photographed by Scott Surner. Notice clean white belly and yellow bill with dark ring. What a difference good light makes in a photograph.

Cory's Shearwater
Calonectris diomedea borealis


Northern Hemisphere Breeders
All forms of Cory's Shearwater complex including the Cape Verde Shearwater discussed below breed in Northern hemisphere. They are working during our pelagic birding season in the summer. Birds seen on summer trips are probably non-breeders. Breeders may appear in our waters in fall.

The Cory's Shearwater (C.d. borealis) commonly seen in New England breeds on islands on the other side of the ocean outside of the Straits of Gibraltar including: Berlengas (portugal),Madeira, Desertas, Salvages, Azores, and Canary Islands. Disburses after breeding to south Atlantic and Indian Oceans. On pelagic trips you may hear the announcer refer to this bird by the species name of Borealis.

Separate Cory's Shearwater from Great Shearwater
The taxonomy of the Cory's Shearwater is currently undergoing change.  Until recently it was assumed that all Cory's Shearwater seen in New England were of the subspecies  Calonectris diomedea borealis.  Increased interest in pelagic birding has resulted in more pelagic trips and subsequently more study.  Digital photography has really changed the scene.  When the webmaster first started taking pelagic trips on almost every trip there was a bird a few people got good looks at before it flew away.  Identification arguments persisted for years after the trip.  Now with so many photographers aboard taking multiple pictures these arguments can be resolved.  Added to all these changes is the fact that for reasons unknown we are now seeing many more Cory's Shearwaters in New England waters than before.  We now know that all of them are not C.d. borealis.

Before you start worrying about separating the subspecies (or full species) of the Cory's Shearwater Complex, learn to separate Cory's from the more common Great Shearwater.

Identification of Cory's Shearwater C. d. borealis
Cory's is slightly larger and heavier than the Great Shearwater and displays a yellow bill with a single dark spot. Flight is slower than Great Shearwater. Wings more bowed when gliding.

Cory's has an all gray head and does not have a dark capped appearance like that of the Great Shearwater. It does have the white rump patch like that of the Great.

As you can see in the Scott Surner photo above the belly is clean white without the spotting of the Great Shearwater. Joe Sutherland's photo of Cory's Shearwater at right.

Cory's Shearwater J. Sutherland
Cory's Shearwater with Great Shearwater Joe Sutherland

In this photo by Joe Sutherland four Cory's Shearwater rest on the water with one Great Shearwater ( third bird from the left).  The Cory's are distinguised by their gray heads and yellow bills and also their slightly larger size.

How To See Cory's Shearwater
Because this bird breeds in the Northern Hemisphere it is more likely to be seen late in the summer and into the fall. Usually seen in small numbers (0-2) on Stellwagen Bank July - August. Larger flocks of up to 40 birds may be seen south of Cape Cod.

In the summer of 2009, relatively large numbers of Cory's Shearwaters were seen off the coast of New Hampshire in spring and fall. This phenomenon has proved to be somewhat eratic with some years producing more Cory's than others.

The Cory’s Shearwater Complex

Cory's Shearwater was once considered to be three distinct species. The three species were lumped into one species named Cory's Shearwater with three subspecies each having a distinct breeding range.

Now taxonomists are having second thoughts and recently the subspecies Calonectris diomedea edwardsii has been elevated to separate species endemic to the Cape Verde Islands. At present most sources consider Cory's Shearwater to have two subspecies. Others have already elevated the subspecies to three full species. The following chart outlines the evolving taxonomy of the Cory's Shearwater Complex.

Clements 2007

Breeds / Disburses


Proposed


Cory's Shearwater

     Calonectris diomedea diomedea


Mediterranean Islands: Balearic, Malta, Sardinia, and islands of France, Algeria, Tunisia, Italy, Greece, and Croatia.

Disburses past the strait of Gibaltar to the North Atlantic.where it occurs west to the coast of North America. Moves south in winter in the Atlantic off the coast of Nambia and South Africa and some into the Indian Ocean.

Scopoli Shearwater

      Calonectris diomedea



    Calonectris diomedea borealis

Berlengas (portugal),Madeira, Desertas, Salvages, Azores, and Canary Islands.

Disburses to south Atlantic and Indian Oceans

This is the subspecies most often see on the
coast of New England a
nd usually called as
“Cory’s.Shearwater” or “Borealis.”

Cory's Shearwater

        Calonectris borealis

Cape Verde Shearwater

    Calonectris edwardsii

Cape Verde Islands endemic. Feeds in local waters during breeding.

Disbursal not well known perhaps off the coast of
Senegal. One recorded off North Carolina. Not yet identified in New England waters.


Cape Verde Shearwater

        Calonectris edwardsii

Separating Cory's Calonectris diomedea borealis And Scopoli Shearwaters Calonectris d.d.
Once you have identified a Cory's Shearwater and not a Great Shearwater you can turn to making sure it is not a Scopoli Shearwater. To do this you need a good shot at the underwing.

The Cory's Shearwater has a larger dark tip with an abrupt line separating white and dark. The Scopoli has a smaller dark tip with fingers of white due to the pale bases of the primary feathers. This is a good time to have some good photographers aboard.

Cory's Shearwater Jeff Slovin  (borealis)     
 

 

 

 Cory's Shearwater above photographed by Jeff Slovin on June 2010 BBC pelagic to continental shelf edge. Underwing of the Cory's Shearwater show the abrupt separation of the dark wing tips from the underwing coverts

Scopoli Shearwater Jeremiah Trimble bird 1

Underwing of the Scopoli Shearwater above shows a " smaller dark tip due to paler bases to the primaries." (Olney 2007)
Scopoli Shearwater Calonectris diomedea boroli photographed on 7/19/2008 BBC Extreme Pelagic by Jeremiah Trimble and labeled Bird #1.


Scopoli Shearwater Jeremiah Trimble 7 /19/2008

Scopoli Shearwater 7/19/2008 by Jeremiah Trimble labeled Bird  2

Scopoli Shearwater Jeremiah Trimble Bird 4

Scopoli Shearwater photographed by Jeremiah TGrimble and labeled Bird 4.  7/19/2008

For some excellent photographs of Scopoli Shearwater from Italy
 http://www.pbase.com/search?q=scopoli+shearwater&b=Search+Photos&c=sp

Cape Verde Shearwater C. edwardsii (Oustalet, 1883)
Once considered a subspecies of Cory's Shearwater, the Cape Verde Shearwater has recently been split off as a separate species. It is endemic to the Cape Verde Islands. It has an all dark, slim bill, and darker head and upperparts than Cory's. The flight has been described as rather more typically shearwater-like than Cory's, with stiffer and more rapid wing beats. (Onley 2007)

The Cape Verde Shearwater has not been identified in New England waters. We are looking for it.

Scopoli Shearwaters in New England Waters
A Calonectris shearwater was tentatively identified and later confirmed to be Calonectris diomedea diomedea or Scopoli Shearwaters on the 2006 Extreme Continental Shelf Edge pelagic. There were some excellent photographs taken of this bird some of which the author does not have permission to use on the web page.

On the July 2007 trip another bird was identified as a possible Scopoli Shearwater.

On the 2008 July trip to Atlantis Canyon 4 birds were well photographed by Jeremiah Trimble and his photographs are used above to help with the field separation of Cory's and Scopoli Shearwaters.


Now that we know it is possible to encounter both subspecies in our waters, birders should familiarize themselves with the identification of both subspecies and look for Scopoli types on all pelagics. I think it is beneficial to preserve Rick Heil's detailed notes from the trips on which the Scopoli was first identified.


The First in 2006- Comments on the probable "Scopoli's" Shearwater (from Rick Heil 2006 Shelf Edge Trip):
“Distinctly smaller, slenderer, and slightly darker Cory's-type shearwater with a darker, shorter, and more slender bill repeatedly followed and readily picked out and observed from a roosting flock of Cory's and Greater along the shelf edge west of Hydrographer. A number of photographs were taken of the bird on the water and in flight. Possibilities include Cape Verde Shearwater (C. edwardsii), in N. Am. recorded once off Hatteras, NC (15 Aug. 2004), or 'Scopoli's Shearwater' (C.d.diomedea), the Mediterranean race of Cory's. “

Follow-up from Rick Heil (posted 8/28/06):
“After reviewing some (but not yet all) of the photographs of the Calonectris Shearwater near Hydrographer Canyon (taken by Blair Nikula, Joe Sutherland, and Dave Larson) on Saturday's Pelagic, I believe the bird to be of the Mediterranean race of Cory's Shearwater, C. diomedea diomedea, also known as SCOPOLI'S SHEARWATER.
Interestingly Petersen and Veit mention C.d.diomedea (Scopoli's) in the Birds of Massachusetts as being known from specimens off Long Island, and 'kind of' predict its potential appearance in New England waters.”

Seabirds  |  Shearwaters  Index  |  Great  |  Sooty  |  Cory's  |   Manx   |  Audubon's   |  Little | Top of Page       Comments to webmaster

Harrison, Peter (1983) Seabirds an identification guide Houghton Mifflin Company; Boston

Howell, Steve N.G. (2012) Petrels, Albatrosses & Storm-petrels of North America A Photographic Guide Princeton University Press; Princeton

Olney, Derrick and Scofield, Paul (2007) Albatrosses, Petrels & Shearwater of the World Princeton University Press Princeton