[CT Birds] scaup vs scaup

greg hanisek ctgregh at yahoo.com
Wed Nov 30 15:32:46 EST 2016

I spent an enjoyable 20 min+ this morning studying a mixed flock of 6 scaup on mirror flat Lake Waramaug in New Preston. The birds were at close range (good views with bins; very detailed views with scope). Since this is a well-known ID trouble-spot I thought it would be worth explaining my methods (which have been sharpened considerably by spending time with eBird reviewer Ian Worley of Cornwall, VT, for hours in winter 2015-16 under the Champlain Bridge on the VT side of L Champlain). This spot can hold many hundreds to several thousand of both scaup, each in significant numbers. Ian is a real stickler for accurate counts and/or good ratios. Trying to produce both with bitter winds whipping across the lake and churning the surface can turn production of a reasonable eBird checklist into a humbling experience. But it does teach how variable the shapes of these bids can be when not swimming on a placid surface.
Waramaug was "Lake Placid" this morning, but it still took some patient watching to see each bird in a position that allowed for a confident species ID. When working on these birds here are 4 things to look for (none was an adult male) 1/ overall size comparison; 2/ bill size comparison; 3/ head shape of bird in profile with erect posture 4/ head shape when seen from directly behind. (A stretched wing will of course clinch things).
1/ When seen side-by-side, the Lesser will look smaller and especially less bulky than the Greater; 2/ Again side-by-side, the Lesser's bill will look smaller and less formidable than the Greater's; 3/ In a good profile view the Lesser's head will show a small but obvious knob or knot at the rear crown, so the high spot on the head is behind the eye; Greater will show a more evenly sloping crown (the high spot may not be obvious but it will be above or in front of the eye; 4/ Try to observe the back of the head, being patient enough to get a view from directly behind if possible. In this view the head pinches in a bit at the eyes; you want to look at the area above this "pinch" - in Lesser this area is higher and narrower; in Greater it's lower and wider.
BUT ALWAYS NOTE HOW MUCH HEAD SHAPE CAN CHANGE WHEN THE BIRDS ARE ACTIVE OR HAVE HEADS TUCKED. However, sometimes the Lesser's "knot" really sticks out on a tucked head.
Greg HanisekWaterbury

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