Hayden, of Ardgowan School, asks :-
Why do birds travel in a flock?
Kerry-Jayne Wilson, an Ecologist with the Department of Entomology and Animal Ecology at Lincoln University, responded.
Groups of birds travel together for a number of reasons. Probably the two most important are when looking for food and to gain an energy advantage while flying.
When migrating or travelling between feeding or roosting sites the birds at the front of the group break the wind and there is less wind resistance for the birds that follow. In this case all the birds turn together. They invariably take turns at the front.
Also they travel in a group because they are looking for food in which case birds may or may not all turn at the same time. The behaviour of such groups varies from species to species. If food resources are clumped and there is enough for the group, then all members of the group should follow the leader. This might be expected for fruit eating birds where food is patchy, but patches generally are big. If food is scattered individuals may break away from the flock as they reach the feeding grounds. This happens with some seabirds as many individuals in a loose flock have a greater chance of finding food. The birds remain in a group if food is plentiful. If not they go their own way, keeping an eye on their flock companions and join them when food is found. Terns, gannets and some tropical species that rise above the water then drop on to food from above, a behaviour readily seen from a distance, often behave this way.