From the Editor's summary and Couzin's essay in Nature on this topic:
"Watching a giant flock of birds swoop across the sky as one, or a school of fish darting this way and that, it's impossible for our minds to conceive of a process that unites so many individuals so seamlessly."
"We now know that such synchronized group behaviour is mediated through sensory modalities such as vision, sound, pressure and odour detection. Individuals tend to maintain a personal space by avoiding those too close to themselves; group cohesion results from a longer-range attraction to others; and animals often align their direction of travel with that of nearby neighbours. These responses can account for many of the group structures we see in nature, including insect swarms and the dramatic vortex-like mills formed by some species of fish and bat. By adjusting their motion in response to that of near neighbours, individuals in groups both generate, and are influenced by, their social context — there is no centralized controller."
"For individuals within groups, survival can depend critically on how local behavioural rules scale to collective properties. Pertinent information, such as the location of resources or predators, may often be detected by only a relatively small proportion of group members due to limitations in individual sensory capabilities, often further restricted by crowding. Close behavioural coupling among near neighbours, however, allows a localized change in direction to be amplified, creating a rapidly growing and propagating wave of turning across the group. This positive feedback results from the ability of individuals to influence and be influenced by others, and allows them to experience an 'effective range' of perception much larger than their actual sensory range."
"We are beginning to comprehend more fully how individuals in groups can gain access to higher-order collective computational capabilities such as the simultaneous acquisition and processing of information from widely distributed sources. Group members may come to a consensus not only about where to travel but also about what local rules to use. Thus, like the brain, groups may adapt to compute 'the right thing' in different contexts, matching their collective information-strategy with the statistical properties of their environment."
"...today there is a rapidly expanding and vibrant community of biologists, engineers, mathematicians and physicists for whom flocking serves as inspiration. Such group behaviour holds clues about the evolution of sociality, and also for the development of novel technological solutions, from autonomous swarms of exploratory robots to flocks of communicating software agents that help each other to navigate through complex and unpredictable data environments."