Many species of bird migrate northwards in the spring to take advantage of the abundance of nesting locations and insects to eat. As the availability of food resources decreases during the winter to the point where the birds cannot survive, the birds migrate south again. Some species are capable of flying all the way around the earth. The act of migration itself can be risky for birds due to the amount of energy required to sustain flight over these long distances. Many juvenile birds can die from exhaustion during their first migration. Due to this inherent risk of migration, many species of birds have acquired different adaptations to increase the efficiency of flight. Flying with other birds in certain formations can allow their flight patterns to be more energy efficient. The Northern bald ibis migrates from Austria to Italy. The behaviour of these birds is such that they migrate together within a flock and each individual bird continuously changes its position within the flock. Each individual bird benefits by spending some time flying in the updraft produced by the leading birds and a proportional amount of time leading the formation. Although it would theoretically be possible for an individual bird to take advantage of this energy-efficient flight without leading the formation itself, no Northern bald ibis has been shown to do this.

Question: All migrating birds do so in flocks to increase their efficiency
Options:
A. true, B. false, C. uncertain
Answer: "C"