Our eighth CES session today caught 28 new birds (and 2 retraps) and was dominated by warblers, making up 64% of the catch, and though most were juveniles we were still able to compare some adult with juvenile plumages.
Photo 1 shows two lesser whitethroats: the iris of the adult on the left is hazel and shows a (just visible in the photo) whitish crescent above the pupil whilst the iris of the juvenile on the right is uniform dark grey.
Adult lesser whitethroats complete their full annual moult after breeding and before migrating back to Africa and so are very worn at this time of year, recently fledged juveniles have fresh plumage as shown by the comparison of the two tails in photo 2.
Adult sedge warblers complete their full annual moult on their African wintering grounds and so are quite worn by July compared to fresher juveniles. Juveniles can also by told by the dark brown speckling on the breast which forms a ‘gorget’ (see photo 3) whilst adults have an unstreaked breast.