An arctic tern, on its 20,000 km flight from the extreme south of South America to the Arctic circle, will take no notice of a nice smelly herring offered from a bird-watcher's boat along the way.

北极燕鸥在从南美洲的最南端飞往北极圈的路线全长2万公里，但燕鸥这一路上都不会留意观鸟船送来的散发臭味却又可口的鲱鱼。