Country diary: How does a bird know what it can share the sky with? | Derek Niemann

Sandy, Bedfordshire: The nearby aerodrome regularly sends up giant flying beasts to about buzzard height, to the apparent indifference of local birdlifeOut of a near cloudless sky comes a low, hornet-like drone, announcing the arrival of a flyer many times bigger than any of the neighbourhood birds. It is a localised summer regular and, over decades, I have learned to narrow down this particular sound to two similar species.More than a century ago, a previous country diarist watched and listened