While flocking, birds adhere to three rules. The first rule is separation, or when a bird turns in order to avoid colliding with another bird of the flock. Cohesion is when birds fly closer together, but avoid direct contact. The final rule is alignment, which is the act of birds turning to follow the same direction of the flock. Separation is the most important rule as it overrides cohesion or alignment. These rules act as traffic laws for flocking birds while migrating.
Migration is one of the primary reasons birds form a flock. Birds migrate between their winter and summer residences to avoid harsh temperatures. The location of a flock's residence varies between bird species. Once a flock arrives at one of their residences, the specimens disperse for the season to develop nests. Nesting usually occurs at a bird's summer residence. Some bird species, such as gannets and swans, are long distance migrators that travel thousands of miles between residences. However, many smaller passerine, such as blue jays and robins, and wetland birds, such as ducks and herons, only migrate several hundred miles.
During the migration, bird flocks periodically land on the ground to roost. Roosting is when bird flocks find a tree to stop for an overnight rest. After finding a roost, the flock searches an area for foraging, or eating food. Depending on the bird species, flocks feed in grassland, aquatic and forest areas. Also, bird species often share the same feeding area with birds from other flocks or species. Flocks find two or three different foraging areas throughout the day. After foraging for most the day, flocks fly back to their roosts for the night before returning to their migration route in the morning.
Mathematicians develop algorithms based on the behavior of bird flocks. These equations are known as flocking algorithms. Flocking algorithms examine how an individual bird's complex behavior emerges from the rules set by its flock. For flocking algorithm calculations, mathematicians consider the three rules of bird migration: separation, alignment and cohesion. The flocking algorithms from studying birds are used by computer scientists in creating artificial intelligence, says the University of California-Santa Barbara's Media Arts and Technology Program.