Thursday, April 27, 2017

Mew Gull

Very Rare Gull Stops in Fredericton

Mew Gull [Brennan Obermayer Photo]
In the first week of April a large mixed group of migrating sea gulls stopped at Fredericton to feed and rest.  There were hundreds of gulls in this group as they rested on the north side of the river on the ice shelf jutting out from shore into the mostly open river.  Many gulls fed and bathed on the river and others wandered around Carleton Park and the area below the walking bridge (former railway bridge).  This provided a wonderful opportunity to view and study these gulls.

Mew Gull with Ring-billed Gulls [Brennan Obermayer Photo]
Among these gulls was one very rare gull, a visitor from the west, a Mew Gull, Larus canus brachyrhynchus.  The Mew Gull is one of four subspecies of Larus canus.  The Mew Gull is the nearctic species (North America and Greenland).  The others are Common Gull (Europe), Russian Common Gull and Kamchatka Gull.

In our area the Mew Gull has to be distinguished from the Ring-billed Gull both of which are shown in the photo above.  The Ring-billed Gull is very common here and can be seen every day sometimes by the hundreds at Carleton Park.  As shown above, the Mew Gull is smaller and has a darker gray mantle (back).

Now let's look more closely at the finer details.  The Mew Gull has a smaller, finer pale yellowish bill which has no ring.  Some individuals, however, have a dusky remnant of a ring that shows as a dusky smudge.  This individual, however, is reasonably clean.  The legs are a yellowish green compared to the deeper orangish yellow legs of the Ring-billed Gull.  The head is smaller and rounder and has a steeper angle above the bill.  The head has significant 'dirty' streaking that shows here compared to the stark white heads of the Ring-bills.  Notice the eye.  The Mew Gull has a dark eye and the Ring-billed Gulls have a  yellow eye.  The Mew Gull has significantly wide white cresents at the trailing edges of the secondary and inner primary  wing feathers.  Notice the two white arcs above the tail on the back.  These are clearly visible as this gull wanders around among a group of Ring-billed Gulls.

Mew Gull [Brennan Obermayer Photo]
There are distinctive differences in wing feather patterns that ornithologists study carefully to distinguish the 4 forms of Larus canus.  Here I'll only mention the large mirrors (white spots) on the P9 and P10 wing feathers (primary feathers).  The real clincher, however, to distinguish this species from the Common Gull is the 'string of pearls' on primary wing feathers P5 to P8.  These are shown in the photo below.  Notice the white dots on the third to the sixth primary wing feather tips coming in from the tip of the wing itself.  This is getting complicated,  so suffice it to say this photo is a wonderful display of a fine distinguishing feature of the Mew Gull.  It clearly shows this individual is a Mew Gull and not a Common Gull.

Mew Gull [Brennan Obermayer Photo]
The Mew Gull lives mainly in western North America where it breeds in British Columbia, Yukon, Northwest Territories, northern Saskatchewan, and Alaska.  It winters along the coast line from northern BC southward to California.  We have very few confirmed records of Mew Gulls in New Brunswick; one from Sheffield in 1969 and just 2 or 3 since.  Most sightings of this group of gulls (Larus canus spp.) in this area are Common Gulls from Europe.

I want to thank Brennan Obermayer for his good work at identifying this bird and for agreeing to share his excellent photos with this blog.  

No comments:

Post a Comment