The Tradeoff Between Territorial Defense and Foraging in the Great Tit (Parus major)

We analyze territorial behavior in terms of decisions about time allocation.Such decisions must be made whenever time invested in territorial defense cannot be devoted to feeding, and vice versa . We describe the ecology and territorial behavior of the great tit ( Parus major ) to show that a tradeoff exists, and then outline a series of laboratory and field experiments in which the value of feeding or defense was experimentally manipulated.Territorial male great tits began to invest more heavily in territorial vigilance after encountering intruders, but the increase in vigilance depended on the rate at which they could feed, as well as their hunger level. We outline a dynamic analysis that takes account of the fact that the optimal tradeoff will change as hunger is reduced. The results of an experimental test of this dynamic model are also presented. We briefly review other techniques whereby territorial tradeoffs have been investigated.