What persuades them to leave the warmth of their wintering grounds and make the dangerous return trip?
Lots of animals make the long trip from the north to somewhere warm when winter arrives. Some species, like the monarch butterfly, make journeys even longer than their lives, taking multiple generations to reach their destination. Migrating means that they don’t have to face freezing temperatures, but something persuades them to leave again and make the perilous passage back to their breeding grounds when the cold months are over. Return journeys are rife with dangers, with the voyagers facing harsh weather conditions, predators, exhaustion and the risk of getting lost.
It’s not all sunshine and relaxation in the southern migratory destinations. The migrant animals have to compete with the permanent residents of their wintering ground for food and space, but when spring arrives in the north and the land begins to come alive again there’s an abundance of resources worth travelling for. Warmer climates tend to have more parasites and diseases, so migratory animals have a better chance of survival and remaining healthy if they go back up north. Returning also means longer days and more time to feed, as daylight further away from the equator varies much more with the seasons.
Migration can occur on an enormous scale – watch this video from Great Big Story for an idea of just how many monarchs fly back and forth between the USA and Mexico each year.