Packed lunches and service stations
Different birds migrate at different speeds, depending on how they get their energy. Small birds like willow warblers use their fat reserves like a packed lunch, to see them through as quickly and directly as possible. They can get from the UK to Africa in less than three weeks. But many larger birds make slower progress. An osprey may take over two months to reach Africa. It can’t store enough energy for non-stop flying, because the extra fat would make it too heavy to fly. Instead it relies on ‘service stations’, such as lakes and estuaries, where it can rest for a while and recharge its batteries with a juicy fish or two. |
