Tony Leukering, a well known author and editor of bird Id articles and
fellow eBird reviewer, published the below post on Scaup ID. The blog post
stemmed from issues we've observed with wintering Greater Scaup in the
Denver area and constant errors in separating Greater and Lesser Scaup, but
the post is quite relevant elsewhere. I thought it'd be worth sharing to
my Tennessee friends as Greaters are appearing to show up more frequently
in winter, esp. in east Tennessee. It's a length and humorous blog post,
but well worth the read.
One take home is the ID is NOT always very straightforward and sometimes
it's best to submit reports using the Greater/Lesser Scaup option.
As a refresher, the following post is an excellent overview of how to use
that "comments" box for flagged reports (or any report!).
Co-Author of *Birds of Tennessee: A New Annotated Checklist