This First-Basic Ring-billed Gull Larus
delawarensis was photographed in mid-December,
1998 and appears to be extremely advanced in replacing its wing
coverts (and even the uppermost tertial), plus the tail is quite
revealing; did it lose a couple of B1 feathers and replace them
with B2 feathers, or is this bird undergoing some kind of non-standard
molt?:   |