01 June 2015

Emergence of 2nd Basic Upperwing Coverts in 1st Summer Ring-billed Gulls

Tis the season. Complete prebasic molts are well underway in our gull species. My local Ring-billeds make observing this phenomenon rather easy, and upon close observation, one can actually see the new 2nd generation wing coverts coming out of their sheaths.

Here's a 1st summer bird that is just now acquiring 2nd generation upperwing coverts (after almost exactly one whole year):

A zoomed-in image of the newly emerged median wing coverts:

Below is the entire range of variability in which these birds replace their wing coverts. Keep in mind all of these birds are in the same age cohort (born in the summer of 2014):

First cycle Ring-billeds. Tinley Park, IL. 01 June 2015.