Do you have a large estate anywhere near you shivvy, as almost all the pheasants in the UK are captive bred just for the gun? (Shooting season Sep - Feb)
As burnhal says they will be nesting soon. Usually April - June and can have as many as 15 eggs, although most are taken by rats and foxes hence the large clutches.
The males occasionally have just the one wife but more often than not (as in your case) a number of females, who live on the male's territory and are exclusively his! Two or three is the norm but some greedy males can have up to 10 wives!!!
In winter pheasants often divide themselves into singe sex flocks, within which there is an establishes hierarchy for feeding and roosting. Many prefer the safety of trees to rooost, out of the way of predators.