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Monday, 30 November 2009

Ageing GREAT NORTHERN DIVERS in early December

Ageing GREAT NORTHERN DIVERS in late November and early December

Last night, admittedly in poor weather conditions, a GREAT NORTHERN DIVER was observed at Brogborough Lake in Bedfordshire which proved far from straightforward to age (see Neil Wright's image at the top of this thread). The bird was very dark and contrasting on the upperparts and showed little 'chequering' on the mantle and back typically seen on juveniles. It was suggested that the bird may be a 'second-winter', described by Lars Svensson as being ''as adult winter, but upperparts darker, and has paler, not so blackish bill-tip and lacks any white-spotted lesser wing-coverts''.

I have put together a gallery of late autumn/early winter photographed GREAT NORTHERN DIVERS to illustrate the key differences.

From Top to Bottom

The Brogborough bird, possibly a second-winter, is followed by a typical ADULT in late autumn, retaining much of its gaudy breeding plumage - this individual photographed at Keyhaven in Hampshire by Alan Lewis on 7 October.

There then follows a number of typical juveniles, all clearly showing the pale fringing on the wing-coverts and upperparts, quite circular in shape, and easy to see - at Draycote Water (Warks) on 22 November (Steve Valentine), three images of the same juvenile in Hartlepool Harbour (Cleveland) on 26 November (Stephen D Keightley), in Newlyn Harbour (Cornwall) on 3 March (Kit Day), at Weybread GP (Suffolk) on 14 December (Rob Wilson), at Draycote Water on 22 November (Carl Baggott) and on Diddington Pit (Cambs) on 28 November (Stuart Elsom).

Towards the bottom of the gallery, I have included images of Great Northern Divers photographed this past week - a juvenile at Belvide Reservoir (Staffs) on 28 November (Steve Nuttall) and adults still largely in breeding plumage at Shustoke Reservoir (Warks) on 28 November (Dave Hutton) and at Carsington Water (Derbyshire) at the same time (Glyn Sellors)