30 August 2015

Late August Ring-billed Gulls and a Juvenile Herring

August is quickly coming to an end. The majority of hatch year Ring-billeds are showing noticeable post-juvenile scapulars - some with only a few new feathers here and there, while others with a complete new set of scaps.

Juvenile Ring-billed. Ghost Type. No "renewed" scapulars shown. Chicago, IL. 29 August 2015.
Juvenile Ring-billed. Cinnamon Type. Note the row of missing juvenile scapulars. 2nd generation scapulars (short, dark gray) are beginning to take form. Chicago, IL. 29 August 2015.
Ring-billed Gull in formative plumage. Virtually all of the juvenile scapulars have been replaced via the preformative molt. Also, a couple of median coverts, as well as the lowest tertial, appear non-juvenile. Chicago, IL. 29 August 2015.

Very advanced for late August. Preformative molt seems to have included more than half of the median coverts and nearly all of the scapulars. Note the single advanced, gray, tertial but with brown shaft streak. A bit confounding is the bases to the upper tertials which are advanced gray as well. See below for the left wing. Chicago, IL. 29 August 2015. 

Slightly less renewed upperwing median coverts on this wing. The lowest tertial seems to have a brown center (barely showing here). Open wing shots below.


For the sake of not having August end without posting a single Herring photo, now this:

Classic Smith! Chicago, IL. 29 August 2015.

Basal 2/3 of bill beginning to pale and a few renewed scapulars (see below).
Dark gray splotches are post-juvenile. My guess is juvenile feathers that are replaced this early are weak feathers that fall out in earnest, probably before fledging. Finally, I've never really paid much attention to the broad white tips to the lowest scaplulars. After looking back at photos from previous years, I guess this isn't an uncommon feature on my local HERGs on Lake Michigan.

No comments:

Post a Comment