If the head of the American state is to be believed, sex is a simple story and gender a guilty fiction. There are male and female – the rest is unnatural. But nature hides a more complex diversity. The ruff is a magnificent example.

This small wader from the wetlands of northern Europe and Asia has not one but three types of male, differing in appearance and reproductive strategy. At mating season, the independents don shiny feathers and an impressive black ruff and gather in arenas. There, they compete two by two, under the gaze of the females. At the end of the tournament, the females choose one or more. Not very moral, but not at all surprising.

Except that on the outskirts of the "lek" (the original Swedish name given to these rings), other males seem to be keeping score. With their more discreet plumage and clear white burrs, these "satellites," as the scientists have dubbed them, have formed an alliance with one of the fighters. When the time comes, they'll share access to the females with him.

Finally, scientists have more recently discovered a third, much rarer type of male, known as faeders. Identical in size and appearance to the females, they mingle with them and take advantage of the ambient furia to stealthily copulate.

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