The strange case of the homosexual necrophiliac duck pushed out the boundaries of knowledge in a rather improbable way when it was recorded by Dutch researcher Kees Moeliker.

It may have ruffled a few feathers, but it earned him the coveted Ig Nobel prize for biology awarded for improbable research, and next week he will be recounting his findings to UK audiences on the Ig Nobel tour.

Ducks behave pretty badly, it seems. It is not so much that up to one in 10 of mallard couples are homosexual - no one would raise an eyebrow in the liberal Netherlands - but they regularly indulge in "attempted rape flights" when they pursue other ducks with a view to forcible mating. "Rape is a normal reproductive strategy in mallards," explains Mr Moeliker.

As he recounts in his seminal paper, The first case of homosexual necrophilia in the mallard anas platyrhynchos, he was in his office in the Natuurmuseum Rotterdam, when he was alerted by a bang to the fact a bird had crashed into the glass facade of the building. "I went downstairs immediately to see if the window was damaged, and saw a drake mallard (anas platyrhynchos) lying motionless on its belly in the sand, two metres outside the facade. The unfortunate duck apparently had hit the building in full flight at a height of about three metres from the ground. Next to the obviously dead duck, another male mallard (in full adult plumage without any visible traces of moult) was present. He forcibly pecked into the back, the base of the bill and mostly into the back of the head of the dead mallard for about two minutes, then mounted the corpse and started to copulate, with great force, almost continuously pecking the side of the head.

"Rather startled, I watched this scene from close quarters behind the window until 19.10 hours during which time (75 minutes) I made some photographs and the mallard almost continuously copulated his dead congener. He dismounted only twice, stayed near the dead duck and pecked the neck and the side of the head before mounting again. The first break (at 18.29 hours) lasted three minutes and the second break (at 18.45 hours) lasted less than a minute. At 19.12 hours, I disturbed this cruel scene. The necrophilic mallard only reluctantly left his 'mate': when I had approached him to about five metres, he did not fly away but simply walked off a few metres, weakly uttering a series of two-note 'raeb-raeb' calls (the 'conversation-call' of Lorentz 1953). I secured the dead duck and left the museum at 19.25 hours. The mallard was still present at the site, calling 'raeb-raeb' and apparently looking for his victim (who, by then, was in the freezer)."

Mr Moeliker suggests the pair were engaged in a rape flight attempt. "When one died the other one just went for it and didn't get any negative feedback - well, didn't get any feedback," he said.

His findings have provoked a lot of interest - especially in Britain for some reason - but no other recorded cases of duck necrophilia. However, Mr Moeliker was informed of an American case involving a squirrel and a dead partner, although in this case it is not known whether the necrophilia observed was homosexual or not as the victim had been run over by a truck shortly before the incident.