Thanks to the consistently tactful yet clear comments provided by
Bob Ringler and Gene Scarpulla,  I have submitted the Ocean City Thayer's
Gull sighting to "further review" and the result is to down grade it to only
(at most) a "possible" Thayer's Gull over there that day. Gene's detailed
comments (forwarded below) included a fine description of what we needed to
see in order to be confident of Thayer's Gull instead of merely a Herring
Gull that happened to differ quite a bit in jizz and markings from the other
Herring Gulls on the parking lot that day.  If the bird we saw was indeed a
Thayer's Gull, it managed to sneakily fly away without fully disclosing that
identity to us.
	Gulls are fascinating indeed, and do provide a great challenge for
identification.  My hat is off to those who have become experts in sorting
them out, and greatly appreciate folks  taking the time to contribute to the
education of some of the rest of us.
	
Les Roslund


-----Original Message-----
From: Eugene J. Scarpulla [mailto:[log in to unmask]] 
Sent: Monday, February 07, 2005 5:51 PM
To: 
Cc: 
Subject: Re: [MDOSPREY] Thayer's Gull and Iceland Gull in Ocean City


Les,

(Tom, I just noted your post, so I CCed you as well.)

I have seen several adult Thayer's Gulls in Maryland over the last 15 or so 
years.  Mostly they have been at Conowingo Dam, but occasionally at 
landfills.

Your description of the unusual gull is consistent with a Herring Gull. 
Gulls are sexually dimorphic in size.  Females are smaller than males, and 
occasionally you will come across a very small or very large bird that is 
presumably a female or male respectively.  The heavily streaked head and 
neck of some adults at this time of the year indicate "winter" head plumage 
(although you do also find this in summer immatures).  It can be highly 
variable from light to heavy.  (Tom this is also the case in adult Lesser 
Black-backed Gulls in winter and is used to distiguish between different 
birds.  Some adult Lessers have virtually no head or neck streaking in 
winter.)

As you stated, a large bill could indicate an old bird or a bird with a bill

deformity.

A standing adult Thayer's Gull is virtually indistinguishable from an adult 
Herring Gull unless you are close enough to observe a "darker-than-yellow" 
iris or that the primaries are charcoal-colored and not black.  The best 
thing that could have happened for you would have been for the gull to flush

so that you could observe the upper and under wing patterns.  The underwing 
of a Thayer's would be all white except for charcoal-colored subapical spots

on each outer primary.  The upperwing of a Thayer's would have outer 
primaries that would each have a mostly charcoal-colored outer vane with a 
mostly whiteish inner vane.  The upper wing outer primaries would exhibit a 
striped appearance when in flight.  The best depiction that I have seen of 
these characters are the "Adult nonbreeding" Thayer's Gull in flight on page

218 of The Sibley Guide to Birds.   Compare this to the typical pattern of 
the "Adult nonbreeding" Herring Gull in flight on page 216.  But, you need 
to be cautious of the "Paler adult non-breeding" Herring Gull in flight on 
page 216.  I have seen many of these pale Herrings at Conowingo Dam over the

years.

I hope this is of some help.  Keep looking at gulls.

Gene

Gene Scarpulla
Millers Island, Maryland



----- Original Message ----- 
From: "Les Roslund" <>
To: <>
Sent: Monday, February 07, 2005 9:51 AM
Subject: [MDOSPREY] Thayer's Gull and Iceland Gull in Ocean City


Saturday afternoon, -----