03 December 2012

Pinkish Bills in Adult-like American Herrings

Here's an adult-type American Herring with a mostly pink bill:

Milwaukee, WI. 02 December 2012.
The visible primaries have a perfectly looking adult aspect and the upperparts appear solidly gray, but the bill pattern suggests a sign of immaturity.

Here's what the open wings and uppertail look like:

Note the dirty alula and marked rectrices. This individual is not a definitive adult, but rather, a 4th cycle bird.

Also of interest are the bold black outlines to the shafts of the the primaries and greater primary coverts. Is this another sign of immaturity?