22 May 2016

Prebasic Molts in 1st Cycle Ring-billed Gulls

1st cycle Ring-billed Gulls typically begin their prebasic molt in mid-May. The molt is initiated, or at least detected, by the dropping/replacement of the innermost primaries.

Typical mid-May Ring-billed Gull (second calendar year).
The 3 innermost primaries have dropped. Tinley Park, IL. 21 May 2016.
1st Summer Ring-billed with obvious molt gap where the secondaries & primaries meet.
 The innermost primary and outermost secondary have emerged.
Tinley Park, Illinois. 07 May 2016.

This individual has dropped a few secondaries and a couple of primaries:

P1-P2 new. P7 appears 2nd generation. Tinley Park, IL. 21 May 2016.
Interestingly, p7 on the left wing is 2nd generation. This feather has an odd-shaped tip that's emarginated. It's also a bit worn. It very likely replaced an accidentally dropped juvenile primary (as opposed to being part of the current primary molt). Note p7 on the right wing is still juvenile (1st basic).

Same individual above. Both P1-P2 new. P7 old. 
Most adults haven't begun dropping/replacing primaries or rectrices yet (i.e., the prebasic molt). They begin molting almost an entire month (or two) later than 1st cycles. The demands of courting, pairing up and nesting are taxing enough and hence molt is delayed.