| vigilance and fitness in grey partridges perdix perdix: the effects of group size and foraging-vigilance trade-offs on predation mortality. | 1. vigilance increases fitness by improving predator detection but at the expense of increasing starvation risk. we related variation in vigilance among 122 radio-tagged overwintering grey partridges perdix perdix (l.) across 20 independent farmland sites in england to predation risk (sparrowhawk accipiter nisus l., kill rate), use of alternative antipredation behaviours (grouping and use of cover) and survival. 2. vigilance was significantly higher when individuals fed in smaller groups and in ... | 2007 | 17302828 |