This is especially important in stressful winter conditions. Flocks may confuse predator when they can't isolate an individual to prey upon. This decreases the amount of time that an individual must spend watching for predators, so it increases the amount of time available for foraging. Disadvantages - The main disadvantage is increased competition for available food. This type of organization exists in many colonial or flocking birds.
Dominance is maintained by ritualistic threat displays.
Body Size - generally larger birds dominate smaller birds. The size of roosting flocks varies from a few individuals in a single tree to millions of individuals in a small area. Niche Partitioning to Reduce Interspecific Competition - Competition among species for limited resources is the single most important force shaping community structure. This allows coexistence of several species within the same habitat. Each species specialized on a different portion of the tree, and each foraged in a slightly different manner.