In the upper image, two same aged 2cy LBBG are depicted. Note the difference in pattern of the third generation feathers. In the front bird, those third generation median coverts, central tertial, most of the scapulars and first greater covert have been renewed for adult-like grey feathers. Practically the exact feathers are renewed in the other 2cy as well, but here the pattern is much more 2^nd generation-like, with a sub-terminal bar and a pronounced dark shaft streak, visible in scapulars, coverts and tertials.
Note the very abraded scapular covert.
In the background: note the difference between the grey tone of the two LBBG. In the far background a Herring Gull.