The size of a flock of redshanks affected the method of hunting used by two species of raptors. Predators have various modes of hunting that are determined by the response of the prey. Sometimes it is more appropriate for the prey to be chased down before it is captured or killed. Other times it is more appropriate for the prey to be caught by surprise. In this study the size of the redshank flock determines which method the raptors will use in order to obtain the most successful attacks.
If the flock size of redshanks increased, the attack success of peregrines declined when using the surprise –attack and the nonsurprise-attack. The sparrowhawks attack success declined when using the surprise-attack only. The sparrowhawks attack success did not decline when it used non-surprise attacks because it only used this mode of predation when it was already spotted by the redshank. The Peregrine falcon and the sparrowhawk varied in hunting style only when a flock of redshanks was large. The sparrowhawk hunted mostly from cover and the Peregrine falcon preferred to attack from the open where the prey could see him. When the prey lived in a smaller flock, they relied on vigelence to protect against predators. When the redshanks lived in a larger flock, they relied more on the confusion effect.
When the surprise attack mode of predation was used, the success of attacks involving both species of raptor decreased as the population of the prey increased. This leads us to the conclusion that having a greater number of redshanks in a flock will ensure the highest rate of survival for the flock.
Check out this video of a peregrine falcon attacking a grouse!