24 February 2011

Pale Thayer's or Dark Kumlein's?

I headed back up to North Point Marina a few days after the Gull Frolic. It was nice being there on a weekday and having the gulls to myself for uniterrupted study. My numbers were similar to those I had at the frolic, but I did not relocate the white-winged 3rd cycle Kumlien's. Instead, I found a 3rd cycle bird that, again, challenged my Thayer's-vs-Kumlien's identification skills:

3rd cycle Thayer's/Kumlien's type. Winthrop Harbor, IL; 23 FEB 2011.
From certain angles, the wingtips and tailband seemed paler than the almost black 3rd cycle patterns I associate with Thayer's. The upperwing coverts seemed to be washed with a paler brown tinge (2nd generation?).

The mirror on P10 supports 3rd cycle. Bill size is also a plus for Thayer's. 
California birder Steve Hampton commented on this bird and thinks there is no reason to suggest Kumlien's or an intergrade - I tend to agree the more I look at the dark primaries. He added that there are currently hundreds of Thayer's Gull in his part of California at the Davis Wastewater Treatment Plant (outside of Sacremento) that are even slightly paler than this bird. 

Here are two more flight shots of this Thayer's Gull:

If you haven't been exposed to Thayer's and/or Kumlien's on Lake Michigan, then be cautious when identifying these two. We have, in my opinion, the highest rate of intergrades anywhere in the lower 48 states. I continue to encounter more and more individuals that I don't feel comfortable assigning to either taxon. I'm sure my inexperience is partially to blame, but even some of Illinois' greatest birders are regularly humbled by problematic Thayer's/Kumlien's intergrades that don't seem to show textbook marks.

Anywho, I was glad to get several other Thayer's and Kumlien's (at a distance) on this day. I also enjoyed this 1st cycle Glaucous Gull that spent a good amount of time coming in for chum:
1st cycle Glaucous Gull. North Point Marina; 22 FEB 2011.