[CT Birds] Perfect duplicate birds - more than Meadowlarks

COMINS, Patrick PCOMINS at audubon.org
Fri Jan 9 10:02:46 EST 2009

With some experience Greater and Lesser Black-backed Gulls aren't all that similar at all.  In fact, if you have a question about whether a gull is a lesser or greater, is probably isn't a Lesser Black-backed Gull.

Among other things, the Lesser Black-backed Gulls that are most often seen in our area are slate gray across the back rather than the dark black of a greater...more akin to Laughing Gull than Greater.   Also, adults and subadults have much more streaking on the head in the winter.  They are also quite a bit smaller (generally smaller than Herring Gull) and structurally different than GBB, with smaller bills a more petite head and attenuated rear end caused by the longer, pointy primaries that extend well beyond the tail.  Also they tend to sit on the water with the 'rump' and wings pointed upwards at an angle.

There are also sufficient differences in immature plumages that separation should not be problematic.  I think they are often more difficult to separate from Herring Gull in immature stages than from GBB.  If you do get a darker backed adult or subadult individual of lesser, they tend to be even smaller than our typical specimens and the leg color tends to be brighter yellow.    The real tricky part of Lesser Black-backed Gull ID comes from the extremely rare not the common, as some of the Asian Herring/Lesser complex like heuglini, barbarensis and tamyrensis can be very difficult to separate from LBBG.   If you find one of those though I want to know about it. Hybridization with Herring Gulls, a relatively new occurrence, also can put a fly in the ointment, but shouldn't cause confusion with GBB.

The others are (mostly), less intimidating than you might think with some experience.

Won't speak to Cackling and Canada, since lesser Canada Geese can be problematic but as I recall Mark Szantyr gives this group treatment in a recent Warbler article (more incentive to join COA if you don't belong).

Bill and leg structure and voice should make the yellowlegs readily separable.  In the scaups, head structure allows for separation at reasonably distant range and in flight there is more white in the primaries of Greater Scaup.  Finally, silent empids can be a challenge, but even there, most of our species are separable with careful observations of things like wingbars, eye rings, bill color and structure and primary extension.  Kaufman gives great treatment of this in the Peterson Advanced Birding series.

Hope this all makes sense in my feverish state.

Patrick Comins

Patrick M. Comins
Director of Bird Conservation
Audubon Connecticut
pcomins at audubon.org


Audubon Center at Bent of the River
185 East Flat Hill Road
Southbury,  CT 06488
Phone:  (203)264-5098 x305
or 203-267-6732 x305
Fax: (203)264-6332

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