two common behaviours in flocking birds are guarding and reconnaissance. when a flock of birds is feeding it is common for one bird to perch on a high place to keep guard over the flock. in the same way, when a flock is asleep, often, one bird will remain awake. it is also common for large flocks to send one or two birds ahead of them when they are flying to a new area. the look-out birds can spy the lie of the land to find food, water and good places to perch. mixed feeding flocks occur, and can help to spot predators.