when it visualizes a possible predator. In response the black-capped chickadees within the flock surround the predator and attack it in a mob-like fashion in order to force the predator to leave. This is known as mobbing. This mobbing behaviour is quickly learned by the juveniles within a flock meaning that these individuals will be better equipped as adults to ward off predators and respond rapidly when a predator is in sight. Foraging in flocks Bird species living in a flock are able to capture prey, likely injured, from an unsuccessful bird within its flock. This behavior is known as the beater effect and is one of the benefits of birds foraging in a flock with other birds. It can be seen that birds in a flock may perform the information-sharing model. In this situation the entire flock would search for food and the first to find a reliable food source will alert the flock and the entire group may benefit by this finding. While this is an obvious benefit of the information-sharing model, the cost is that the social hierarchy of the flock may result in subordinate birds being denied food by those that are dominant. Another cost is the possibility that some individuals may refuse to contribute in the search of food and instead simply wait for another member to find a food resource. These individuals are known as producers and scroungers, respectively. An intricate hunting system can be seen in the Harris's hawk in which groups of 2–6 hunt a single prey together. The group splits into smaller groups in which it then encloses on a prey, such as a rabbit, before it attacks it. By hunting as a group the Harris's Hawk is able to hunt larger animals and decrease the amount of energy spent hunting while each hawk in the group is able to eat from the catch. Black sun In the Denmark, there is a biannual phenomenon known as sort sol (Danish for "black sun"). This is when flocks of European starlings gather in vast numbers, creating complex shapes against the sky during the spring. It is during this time spent in Denmark that the European starlings spend time gathering food and resting as part of their migration journey. By being in groups this large the European starlings are able to decrease their risk of predation by hawks. References External links Birds Ethology Group