A dead ringer

Not actually dead, but a close call for a drake Ring-necked Duck. This bird is a hybrid Ring-necked Duck x Tufted Duck, Dunstable Sewage Works, 15th May 2011.

On first glance it shows the sweeping grey flanks, white edged base and ring to the bill, and the high crown of a Ring-necked, but look a bit closer and thing don't start to add up

• The 'high crown' becomes a bit of a tuft
• the sweeping grey flanks aren't sweeping enough, and don't end with a clear white stripe towards its chest
• The bill pattern isn't strong enough, with a very weak sub-terminal band and white basal surround
• A green sheen to the head
  

There are some good comparison photos on Flickr here, on RadioactiveRobins here, on Dave Browns blog here, and on the Birdwatch Irelands website here.