As the beautiful green season slowly comes to an end and the moisture in the air becomes noticeably less, the lush greenery starts to turn to the dryer colours of red, orange and yellow, the days become progressively shorter and the temperatures become comfortably cooler, the most noticeable change for me is the lack in variety of birds. At this time of the year many birds have started their migrations back to where they had come from.
Why would birds migrate? For some of them the migration is thousands of kilometres. Surely staying in one place would be better, less disruptive and certainly less energy consuming? That’s what one would understandably think but the sun is a powerful force, responsible for these mass migrations of many different species of birds. Where the sun is warmer and gives nice long days, these birds follow, for the sun allows an abundance of food sources to thrive in these warmer climates, from insects to a huge variety of vegetation matter. Birds take advantage of this time of richness of food and warmth to have their chicks.
When we think of bird migrations we generally think of journeys of large distances that take a long time, but some birds move much smaller distances, as little as 200 km from an area where food is scarce over the winter months to an area that has enough of a food source to sustain the species for those few months before they move back again, once the rains have come. Of course the famous type of migrations are the ones that happens over large distances, for instance the red-backed shrike (see photograph) leaves its breeding grounds in Europe around August to September and arrives in southern Africa from beginning to middle October. Here they feast on a variety of insect life and sometimes even catch the small birds. After enjoying the food fest of southern Africa, and fattened up sufficiently for its return journey, the little migrant leaves to head back in the first 10 days of April.
A commonly seen eagle on safari is the tawny eagle, and its movements are interesting as they are largely determined by the availability of food. They are particularly fond of hunting quelea from the vast red-billed quelea colonies so as these colonies move from place to place in search of sustenance some tawny eagles follow suit.
For me the most impressive migratory bird is the one that breeds on the Farne Islands of Northumberland.
In July this species flies from the Farne Islands down the west coast of Africa and round the Cape of Good Hope over the Indian Ocean and arrives in Antarctica in November. The bird is the Arctic tern and this round trip the bird does every year works out to about 93 388 km. That’s more than twice the circumference of the planet! Arctic Terns can live between 15-30 years which would work out to 3 million kilometres for the long-lived bird. Quite simply mind blowing!
One of the biggest mysteries in the wild world is how birds are able to make such magnificent journeys across the globe, often returning to the same nest. There are many theories that scientists have come up with over the years but as far as I am aware no one has been able to pinpoint the precise mechanism. The most recent research I have found suggests that the answer may lie in the quantum realm.