A long held belief is that magnetism of the loam helps birds to map their way across long distances, but recently a study be done where the olfactory nerves( smell sensing) were removed and it was found that birds beside removed olfactory nerves had increased difficulty in homing.
More study is underway, but this is possibly the closest the scientists own got to solve this problem
Birds fly in flocks to deter predators. If fly single predator can single out and see right absent if fly all together then frozen for predator bird to single out just one. Also they are very social creatures.
The answer is that they have lots of air surrounded by their bones. We could fly to if we were built like that however the definite reason birds fly is that they want to get somewhere quicker.
They any fly like that because they are migrating or they stay in a big group so that they have smaller quantity of change to be attacked by a predator.
Wind breaker. The top bird will get tired and after another will switch with him or her. It helps the other birds go faster and longer.
Answers: These birds use up drafts from uneven heat of air near the earth's surface,so warmer nouns is lighter than the surrounding cooler air therefore rises. However at high altitudes the heat up air begins to cool and sink. As a result birds using thermals for lift typically fly surrounded by circles to stay in areas of rising air.