På opfordring har jeg forsøgt mig med at forklare mig på engelsk, håber alle forstår
This (to me) interesting Aythya-duck was seen in Maribo Denamrk on October 16th. At first it was hiding in the bushes close to the bank of the lake, and here I thought it was a odd looking Pochard. It was quite dark, and it seemed to have a paler bill, with a black nail and a pale subterminal band. This got my thoughts on a Rehead, but...
After observing the bird doing almost nothing for for an hour or so, the duck suddenly decided to go for a swim, and then some details revealed it as a hybrid.
The bill on a Redhead is a loud, greyish with a black tip, straight cut off to the pale subterminal band and it has long nostrils. The bill on this bird was more shaped like that off a Ferruginous Duck, as it was slim and fine, and also the nostrils was too short for a Redhead. The black on the tip off the bill was not straight cut off, it was also present on the side of the bill up half way to the cutting edge.
The shape of the head should be roundet with a steep forehead on a Redhaed, on this bird i think the crown and nape is to edgy.
The bird was about 10% smaller than the Pochard's, a Redhead should be up to 25% bigger, so this is not good, so this alone reveals it as a hybrid!
The iris was orangeyellow and it might be ok for a Redhead, but I'd like it to be more yellow than on this bird. The bird showed some white on the secondaries, at least more white that it usually is on Pochard. The undertail-coverts was black as it should be on a Redhead and a Pochard, and in the top of the coverts close to the tail it showed some pale/white feathers.
All in all I think the bird is a hybrid Ferruginous Duck X Pochard, due to the shape of the bill and the head, the size of he duck, and the white/pale parts in the secondaries and the undertail-coverts. Ccomments are most welcome.