During the nonbreeding season, Peruvian thick-knees in Chile are reported to have an average of 22.5 birds - a mixture of adults and youngsters - in their flocks. Thick-knees are birds that are seen in large flocks during particular seasons in various regions of the world. However another study involving thick-knees challenged whether or not an animal had to recognize the presence of a predator for protection against it.Īggressive display between two black-headed gulls If this is true, even if the bird that signalled the flock were to die its fitness would not decrease according to Hamilton's Rule. The benefit here is if the members of the flock are genetically related to one another. It is important to note that by making an alarm call to signal members of the flock one is providing the predator with an acoustical cue to the location of a possible prey. This type of behaviour is also seen in some birds. This alarm call of the ground squirrel requires the ability of the animal to first recognize that there is danger present and then to react. This simple example demonstrates that flocks are not only seen in bird species or a herd of sheep, but it is also apparent in other animals such as rodents. The squirrel is then able to use vocalizations to warn conspecifics of the possible threat. It can be seen that by ground squirrels living in colonies, the ability to recognize a predator is rapid. The ability to avoid predation is one of the most important skills necessary in order to increase one's fitness. Ground squirrels in an erect position upon hearing the predation alarm call from conspecifics As well this bird is now less likely to be attacked by a predator because predators have a lower success rate when attacking large flocks.
Despite the fact that this bird is more likely to be a subordinate, its ability to obtain food increases substantially. Those birds that are more rare and therefore less abundant in an environment are more likely to perform in this mixed flock behaviour. It is through this specific behaviour of feeding among vegetation that the gleaners indirectly increase the foraging rate of the sallies. When gleaners obtain meals from vegetation it causes the other prey within the vegetation to be flushed out into the aerial environment. This has been shown to occur during forest fires in which insects have been flushed from vegetation, however this can also be done by the gleaners. Studies have shown that as resources in the aerial environment increase, the flock will possess more sallies than gleaners. On the other hand, gleaners are those that consume prey living within vegetation. Sallies are individuals that act as guards of the flock and consume prey in the air during flight. Within a mixed flock there can be two different behavioural characteristics: sally and gleaner. While mixed flocks are typically thought to be composed of two different species, it is specifically the two different behaviours of the species that compose a mixed flock.
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