Birds are known to migrate from one place to another as the seasons change though there are various types of birds migration. Birds usually migrate to warmer places from places that become colder due to the winters. They go to warmer climates to breed, feed and fly. In some cases they may literally travel across the world to go to a place where spring or summers are starting or has already started rather than going into hibernation. In other cases they do hibernate and load up on food to get ready for the summers to come.
There are various types of birds migration and one of these is long distance migration where the birds may go on for days to reach a place that they find to be suitable to them. Here they form their nests and reproduce. These creatures are genetically programed to follow one another when migrating. It is as if they know that they have to migrate. This migration is latitudinal.
Regardless of the types of migration, seasonal changes and drops in temperature do ‘attract’ or ‘repel’ bird to or from a place. You see, birds do not have thick fur or other features of the sort to help them keep warm in the winters. Their feathers aren’t very good at capturing heat either and so, they need to migrate in the winters because they would die if they did not do so. Plus, there would be no way for them to reproduce because of the same reason and their chicks would die too.
Of the two types of birds migration is short distance migration where the birds merely move along the longitudes and so they go to higher places (longitude-wise) where the temperature is warmer and more comfortable for them to survive in. It is suspected that different birds are programed differently because some of them travel longer distances while others seem naturally inclined to traveling shorter distances. The sizes of the birds may be a reason for this as well- for example, it would be easier for sparrows to travel shorter distances because they are small, have short wings and they may die if they far for too long (provided they are able to do so). In comparison to sparrows, eagles have longer wingers, are bigger in size and they do travel longer distances.
Though initially it was thought that birds felt the need to migrate due to weather only but it was later discovered that food, not only weather, may be a factor as well. By way of example, the Lesser Cuckoo is a bird that breeds in one place and then goes elsewhere in the non-breeding/mating season. So this is one of those types of birds migration that is dependent upon food sources. Though one would think that food supplies and weather go hand in hand, that is not always the case as has been seen in the Lesser Cuckoo birds.
So there are different types of birds migration that are eventually dependent upon different factors.