Slaty-backed Here. Slaty-backed There.

You might recall I found a Slaty-backed Gull in Kenosha County, Wisconsin last month:

Pleasant Prairie, Wisconsin. 10 December 2017. Photo by Amar Ayyash

Yesterday, Carl Giometti found an adult Slaty-backed at Calumet Park in Chicago:

Chicago, Illinois. 09 January 2018. Photo by Carl Giometti.

Now, check out this wingtip composite:

Chicago bird (top) & Pleasant Prairie bird (bottom). Courtesy Greg Neise.

The shortest distance between the two sites.

In particular, consider the pattern of the black subterminal band on p5. The wingtip is a perfect match!

So what's the distance from the RecPlex in Pleasant Prairie to Calumet Park in Chicago? 60 miles. Well, 59.45 miles to be exact. 

Of course the bird very likely took a much more interesting route getting down here.

This is not the first time we've detected our winter gulls roaming the southern Lake Michigan region. The food source is "landfills" and any disruption in the food source (i.e., closed for Christmas, or closed on Sunday) readily gets the birds moving.

As my friend Greg Neise described it, "100 miles is nothing to them. It's like us going to check out a new restaurant in the next suburb over".

It remains to be seen if the Calumet Park bird found by Carl is the same bird currently being seen on the Calumet River. The consensus seems to be "same bird" and I agree completely.