On a regular
basis, and mostly during the summer months, Ring-billed Gulls with
a grayish wash over their plumage, most noticeably on the normally
white parts, show up in the Chicago area. Sometimes this gray coloration
is visible on other parts of the bird. My own rough estimate is that
close to one in every 100 Ring-billed Gulls along the Chicago beaches
in summer shows some amount of this gray wash.
The most likely
cause for the gray coloration is that the bird got into some oil,
and the oil is discoloring the bird's appearance.
Here are some
photographs of one such bird taken by Wouter Faveyts on 29 April 2005
at Chicago's Northerly Island. Wouter is from Belgium and was visiting
the Chicago area at the time. With birds like this, shape and structure
can be valuable clues to the bird's identity. Compare the gray Ring-billed
Gull to its "normal" neighbor.
Here's a more
heavily soiled individual, a first year bird, that Tim Wallace photographed
on 24 July 2007 at the Waukegan beach (Lake County, Illinois).
page was last updated on 14 August 2007.
Contact Geoff Williamson
with any comments, updates or suggestions.