Some observations on the occurrence of three generations of primaries in Common Terns Sterna hirundo

(54° 37’N 1° 10’E; Ward 2000), where we trapped 1,409birds using mist nets during late July to early September,1995 to 2001. The majority of birds were mist -netted atnight using tape lures and painted decoys. As withwaders (Insley & Etheridge 1997), this approach maybias the sample towards immature (R Ward unpublisheddata) or non -breeding birds, although it is unlikely to bebiased in relation to the extent of moult. RMW notedthe age series for each primary on 507 non -juvenile birds.The moult limit between the post-nuptial and first pre-nuptial series can be identified by the degree of abrasionof the feather tips and the greyish bloom that concealsthe underlying dark outer primaries (Ullman 1989, Craik1994). Feathers of the second pre-nuptial moult areseparable from the earlier series by an absence ofabrasion, by being a slightly darker uniform grey incontrast to a faded brownish -grey, and by the waxy sheenpresent on new feathers. First-summer Common Ternsrarely occur in Britain (White & Kehoe 2001) and nonewere included within this analysis.Twenty percent (101) of birds had between one andfour inner primaries of the third age series (Table 1).Sixteen of these birds were actively moulting theirinnermost primaries, which confirms that they were notfirst series primaries in suspended moult. Fifty-two ofthe 507 birds (17%) were ringed as chicks or juveniles,