Bird migration explained at last: It’s all about energy efficiency.
UNITED STATES (WASHINGTON POST) – It’s migratory bird season in much of the United States, when about five billion birds enter the country from the tropics and remind us during their “dawn chorus” that they were the ones who invented the tweet.
The seasonal migration of so many birds is an ecological puzzle. There are roughly 10,600 known species of birds, and most don’t migrate. But about 15 per cent of bird species go on these exhausting, heroic journeys, commuting thousands of miles between their summer breeding grounds and the places they spend the winter.
There’s no obvious explanation for why some bird species are migratory and others are not. Big birds, little birds, loud birds, quiet birds – the migrants come in all shapes and sizes and habits. Even within a migratory species, behaviour can vary wildly.