07 June 2014

Northern-type American Herring Nesting on Lower Lake Michigan

I had the good pleasure of joining Indiana birder and conservationist, Carolyn Marsh, and an associate of hers to a waterbird colony on private property in East Chicago, Indiana, last weekend. The highlight for me was finding a Northern-type American Herring Gull on a nest:

Subject bird, lower right, sitting on nest. East Chicago, Indiana. 01 June 2014.
 The surprise came when this individual got up and opened its wings:
Note the large mirrors on both outer primaries and gray inner webs to P7-P9.
Showing a pseudo-thayeri pattern, this bird's outer primaries are atypical for breeding Great Lakes Herrings.
American Herring Gulls exhibit a tremendous amount of variation, particularly in their wingtip patterns. Generally speaking, "western" birds show more extensive black in the outer primaries and more often show a single mirror on the outermost primary. It's also thought that these birds are overall smaller. "Eastern" adults tend to show less black on the outer primaries, average two mirrors, and are thought to be bigger-bodied. Some of this geographic variation was briefly touched on by Mactavish and Jonnson (Birder's Journal, 2000), but the comparisons made were between so-called Newfoundland birds and Great Lakes birds. The samples were quite small and no in-hand measurements were made. In short, the paper was non-exhaustive, and many of the notes come from wintering birds. 

Currently, there is no agreement on what to call these "populations" because they haven't been described in much detail. Some of the suggested "types" being tossed around include: Northern, Eastern, Newfoundland, Western, Great Lakes, Southern, and Interior...

In a recent discussion on the FB Group, North American Gulls, Alvaro Jaramillo raised these questions:
"If you go north and east from the Great Lakes, where do you think the morphology changes from Great Lakes birds to Eastern/Northern birds? Is it a gradual shift, or do you think there are major breaks somewhere? Where hypothetically are these breaks? Shift from forest breeders to tundra breeders in the north? "

Admittedly, very little has been published on what North American Herrings look like at their breeding colonies throughout the continent. This is a longterm project for anyone who is eager to contribute information on the most widespread, large white-headed, pink-legged, gull species in North America. After seeing this individual, I've begun to rethink what so-called Great Lakes birds really look like. Although this individual is certainly out of the ordinary for us down here, I'm wondering if there are more birds like this nesting on the Great Lakes. Perhaps it's time to closely scrutinize these breeders. 

The most difficult questions to answer will be, 1) Are mirrors age/gender related, or, are there truly differences from east/west and north/south? 2) Is the amount of black in the wingtip age/gender related, or, are there truly differences from east/west and north/south? These questions are nearly impossible to answer without study of, and monitoring of, birds banded as pullus. Other important details that can be sorted out with time, are vocalization differences and morphometrics.  

Nest of Northern-type American Herring.
Other, more typical, nesters from the day:





Describing what various populations of American Herring Gulls look like can be done, but it will take effort. It's my hope that bird banders consider using large, color, bands; Many biologists and ornithologists have already begun using these in North America but we have a long way to go. Also, methodically photographing these birds where they're nesting is just as important. A database of photos should be compiled, and an "average archetype" from each participating region should be suggested and put to the test. 

As always, I welcome your thoughts and comments! Thanks.  

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