Country diary: the house martins have taken their song and departed

Claxton, Norfolk When the amount of aerial plankton in the atmosphere drops, the birds head for Africa

In natural history, it is easy to notice a first for the year, but to be mindful of the last is more difficult. I know that the house martins are gone, yet their going from our village entailed an unremarkable dwindling of sights and sounds, but slowly, like a loss of moisture in a puddle.

I did have one memorable sighting last week in the Yare valley. Over Blackwater, about 40 were pooled above a poplar plantation and in and out of their midst swirled a single lost swift. The martins were smaller, busier, each one with a swept-back wing silhouette, which, depending on the way it turned, was shaped like a broad smile, or frown.