My Ph.D. study already started before I got my M.Sc. degree. It was on a peculiar dimorphism among male ruffs, birds that bear conspicuous ruffs of feathers around their faces. In spring, these males stay together for considerable parts of the day at special sites, most often close to the water (see picture above). Some of the males defend very small territories. Others act as guests of the territorial males. Females also come to the communal places, but only for short visits. They select a male, mate, and depart again. They nest alone, lay eggs, incubate and tend their chicks, also without any help of the other sex. Territorial males sometimes fight. The guests have another appearance, behave submissively and never fight. A male plays only one of the two roles during his whole life. In the past ruffs were rather common in the low parts of the Netherlands. At present, ruffs only pass (less and less) during migration. In very exceptional cases, a few may stay for breeding. 

The drawing above shows a map of a communal site. Each number represents a territorial male. Some territories, those drawn with a solid line, are so heavily treaded that the vegetation is completely lacking. 

Almost all males look differently. Territorial males mostly have a dark plumage (picture above). Males that play the role of guest are usually white (male on the right on the picture below). Females are smaller than males and do not possess a ruff of feathers (in the front on the picture below).

A few years ago l accidentally resumed to study ruffs by participating in the analysis of the incredible polymorphism in their plumages.


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