this is the classic Ig Nobel prize winning article:
The first case of homosexual necrophilia in the mallard Anas platyrhynchos (Aves: Anatidae) by C.W. (Kees) Moeliker (page 243-247)
The complete article in PDF

a Drake mallard (Anas platyrhynchos) in full breeding plumage (left) next to the dead drake mallard (NMR 9997-00232) just after collision with the new wing of the Natuurhistorisch Museum Rotterdam; b the same couple during copulation, two minutes after photo a was taken. [photo: C.W. Moeliker]
On 5 June 1995 an adult male mallard (Anas platyrhynchos) collided with the glass façade of the Natuurhistorisch Museum Rotterdam and died. An other drake mallard raped the corpse almost continuously for 75 minutes. Then the author disturbed the scene and secured the dead duck. Dissection showed that the rape-victim indeed was of the male sex. It is concluded that the mallards were engaged in an ‘Attempted Rape Flight’ that resulted in the first described case of homosexual necrophilia in the mallard.
Correspondence: C.W. Moeliker, Natuurhistorisch Museum Rotterdam, P.O. Box 23452, NL-3001 KL Rotterdam, the Netherlands; e-mail moeliker@nmr.nl
Keywords: homosexuality, necrophilia, non-consensual copulation, mallard, Anas platyrhynchos
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