There is a large amount of ice on Schoolhouse Pond today, and I got the 
chance to scan through a fairly large mixed flock of gulls.  There were large 
numbers of Herring Gulls on the ice, as well as Ring-billed and Laughing Gulls.  
Highlights included a 1st winter Iceland Gull.  I got fairly close views of this 
bird on the ice, including the primaries.

But, the most intriguing bird was a 3rd cycle, dark backed gull.  The bird had 
fairly bright pink legs, but the shade of the mantle was comparable to a 
Laughing Gull (I saw the two birds side by side).  I called Jim Stasz, and we 
took down the details of the bird, and field marks which we noted include:

1. Slate gray mantle (comprable to a Laughing Gull in shade), 
2. Yellow iris
3.  Heavily streaked head and breast
4.  Pink legs
5.  Size of a smallish Herring Gull 
6.  Bright yellow bill, especially on the tip.  Paler yellow on base.  Bright red 
gony spot, most saturated at the gony.  The bill was parallel edged, with a 
weak gony angle.
7.  Tertial crescent extended further onto primaries of folded wing than on 
nearby Herring Gulls.  The tertials were shorter than on Herring Gulls, forming a 
more rounded edge.  Both of these features were noticable in direct 
comparison with Herring Gulls.
8.  In flight, the underwing had a dark trailing edge (slate gray flight feathers)
typical of black-backed gulls, with a noticably broad white trailing edge to the 
upper surface of the wing.  Also noted in flight were the mostly dark wingtips 
(perhaps small white primary spots at most) with a small amount of black in 
the center of edge of the tail.

When we last saw the bird, it was flying towards the Brown Station Road 
landfill.  The Iceland Gull had also apparently left as well.  Unfortunately, 
neither Jim or I had a camera.  But, it was a very interesting gull.  Any 
thoughts or observations are appreciated.  

Fred Shaffer
Patuxent MOS