31 July 2014

Juvenile Ring-billeds: Late July

A small selection of juvenile Ring-billeds, photographed on the very southern tip of Lake Michigan, in East Chicago, Indiana:

Brown type. East Chicago, IN. 26 July 2014.

Intermediate type. East Chicgao, IN. 26 July 2014.
Besides the subtle variation in the bill patterns, also note the immense differences in leg color, so early on in the season.

Ghost type. East Chicago, IN. 26 July 2014.
Peter Pyle recently informed me that it's not very unusual for juvenile feathers to show color patterns that are found in formative feathers. This adds to the excitement of trying to determine whether some of these feathers are juvenile or not, especially with species like RBGU that begin molting in earnest after leaving their natal colonies. Consider this individual:

Ghost type with a considerable amount of gray juvenile feathers. East Chicago, IN. 26 July 2014.
Here's this same individual with outer primary still growing out:

Note the extensive gray in the juvenile greater coverts and in the scapulars sitting over the proximal side of the wing.
I suspect that 2nd generation feathers (whether replacing feathers that were dropped accidentally or via molt) look longer, broader and tend to be "fluffier", covering a number of smaller adjacent juvenile feathers, like this:

Note the long broad, gray, median covert that has a different pattern than the surrounding "true" juvenile feathers.

The progression of 2nd generation feathers is obvious once it begins. Here are several birds that illustrate this nicely, spanning from August through September of their hatch year - all photographed on Lake Michigan: