A couple of years ago, scientists in Japan watched in amazement as three male sand martins tried to have sex with a dead bird lying face down on the ground, which they later learned was also male. Surprisingly, "homosexual necrophilia" is actually a thing among birds, but for sand martins, there's a very reasonable explanation for this odd behaviour. Homosexual behaviour among animals is quite common, particularly among birds. Necrophilia, on the other hand, is rare. The first published description of this twisted sexual behaviour among birds, specifically in mallard ducks, earned Kees Moeliker of Rotterdam's Natural History Museum the Ig Nobel prize for biology in 2003.
As New Scientist reports, another case of avian homosexual necrophilia has been reported, this time by Naoki Tomita and Yasuko Iwami from the Yamashina Institute for Ornithology in Abiko. The abstract of their study, which now appears in Ornithological Science, sums it up quite nicely.
We observed three Sand Martin Riparia riparia repeatedly attempting to copulate with a dead bird lying face down on the ground, with its wings spread and lowered. One of the three remained on the ground close to the dead bird and guarded it against copulation from the other two birds. Then, the guarding bird itself attempted to copulate with the dead bird. Based on subsequent dissection the dead Sand Martin was identified as an adult male.
The researchers say that the apparent homosexual necrophilia could be explained by the fact that physical differences among male and female sand martins are practically non-existent. The lack of sexual dimorphism among these birds likely confused the males, so it was likely a case of mistaken identity.
What's more, the posture of the dead sand martin suggested an open invitation to have sex. "We suggest that posture is an important trigger arousing male sex drive in a sexually monomorphic species," the researchers concluded. So in a manner of speaking, the sand martins were kind of glitching out.
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