At this time every year, we welcome back one of the most charismatic of our summer visitors here in the UK. In April and May, the happy cries of the Barn Swallow can be heard echoing out across our countryside. These tiny birds have travelled and enormous distance to return to our shores, facing many perils in the process including thirst, hunger and becoming somebody’s lunch! But why do swallows go through all the hassle, why not stay here year round?
Many species of birds migrate. The longest flight from take off to landing is currently believed to be undertaken by our very own bar-tailed godwit, travelling a staggering 6,800 miles in one go! From hummingbirds to swans, birds have an incredible ability to migrate vast distances seemingly through instinct and memory alone. We still don’t fully understand how this process works but numerous research project has shed some interesting light on the subject. It has been found that when migrating from Iceland to WWT Martin Mere, Whooper Swans use landmarks to remember when to turn, one of the biggest of which is the Isle of Man.
To undertake these incredible journeys, birds like the barn swallow need a huge amount of energy and a good strategy. During the warm summer months, migrating birds fill up on enough food to see them through their migration. Swallows are insectivorous and will often be seen on a warm summer day chasing flying insects round fields and meadows.
The reason they do all this is because of our climate. In the winter months, Britain’s temperature drops, the trees lose their leaves and many insects hide away and begin hibernating. For the swallows, who eat small flying insects, this means that if they stayed here they may face death through starvation. Instead, they leave our shores and head south to Africa, where the temperature is more than sufficient for their prey. You may then ask why the swallows bother to come back? One theory is the number of predators. In the tropics where it is warmer, there is a highly biodiversity and therefore a high number of species that could hunt young swallows.
When you travel North, the biodiversity starts to decrease because the temperature cools. Therefore nesting in Britain means that swallow families face less of a threat from predation which increases the number of chicks each pair can raise. In this way, swallows must be one of the most dedicated of parents in the bird world, covering up to 200 miles in just one day to reach their nesting grounds!
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