Great Northern Diver - ages

Gavia immer

Observers have seldom included an age assessment in their reports unless noting adults in summer plumage.  

Great Northern Divers have a prolonged post breeding moult period stretching from September to January, consequently birds in summer plumage have been recorded throughout autumn passage, occasionally as late as the end of December. Of a total of 646 birds closely scrutinised passing Strumble Head in autumn, between 1981 and 2008, 48% were in full or showed variable vestiges of summer plumage.

A few birds have been recorded in full summer plumage in the spring, from late April.

Graham Rees

(Covers records up to and including 2008)