The Mating System of the Pheasant Phasianus colchicus.
The aim of this study was to identify the adaptive features of territory defence and harem polygyny in the Pheasant Phasianus colchicus.
I followed, marked and radio-tagged pheasants in a population of about 200 birds inhabiting 150 ha of fragmented woodland and arable fields.
In winter, males form small temporary groups, females large, stable flocks (Chapter 1). By April, most males have established exclusive defended areas along the edges of cover (Chapter 2). In successive years, they expand their territories and some move into neighbouring, vacant areas. Many males remain non-territorial until their second spring rather than defending a poor territory in their first. Territorial males fight neighbours, threaten intruders, crow and display to females (Chapter 3). Females disperse in April and are recruited to male territories as small harems (Chapter 4). Longer established males have larger harems. Each harem has a small home range, mostly confined to one male's territory. Harem members are accompanied by the resident while feeding in the open, but the females sometimes leave his territory, particularly in cover. They allow him to mate with them, but nest outside his territory. They usually return to the same male in the following year.
Territorial harem polygyny has probably evolved in this species because successful males can monopolise areas used by foraging females (open ground close to cover) and females remain gregarious while breeding. Males guard harems against 'rape' attempts by other males; females benefit by reducing energy expenditure during egg-laying.
From a comparison of all genera in the Phasianidae (Chapter 5), I suggest that the need for mate guarding enforces monogamy in open habitats except where breeding females are gregarious. In forests, solitary habits are associated with short pair bonds and promiscuous mating systems. Lek species are comparatively recent colonists of open habitats, descended from promiscuous forest species.