Most of the migrants have been late this year. On a breezy evening of heavy rain, about two hundred hirundines are whizzing about over the lake. They are mostly Swallows and House Martins which have been joined by smaller numbers of Swifts. They seem to be feeding on insects, but it’s hard to believe that such a dense flock of birds could be supported by the flies over a lake on such a chilly, wet evening. The air is busy with the soft, rolling chirps of the House Martins and high, frantic squeaking of the Swifts, with occasional quiet twitters from the Swallows.
I watch for some minutes, enchanted by their mastery of the air and indifference to the rain as they swoop within millimetres of the choppy water, ceaselessly turning, fluttering, rising, swooping and diving. They stay close to the surface most of the time and I wonder if they are feeding on insects emerging from the lake. The Swifts are noticeably big and dark, the stiff blades of their wings winnowing the air between arcing swoops. The Swallows are less robust, fluttering between turns and swooping more sharply and frequently, spreading the fork of the tail to brake and change direction. The House Martins appear a shade more fragile still and are easily distinguished by the white rumps and underparts which flash quickly as they flit and turn.
The Sand Martins arrived over a month ago and their absence is noticeable in this evening’s flock. Recent weeks have been characterized by occasional sightings and the odd small flock of Swallows, House Martins and, more recently, Swifts, but this is the first sizeable gathering of newly arrived birds this year. Their energy is amazing considering they are near the end of an epic flight from Africa.