The walk home has a certain poignancy this evening. Above the riverside limes are swallows and house martins, a gathering of individuals feeding up before departing south. The chattering calls imply a sense of nervous anticipation and emphasise that these evenings will soon slip towards a silence that is broken only by the solitary robin, now delivering his winter song. Only a few brief weeks ago the evening skies rattled with the screech of swifts, their boisterous parties skimming the rooftops and delivering sweeping curves of noise. How quiet it will seem when the last of our summer migrants has gone.
While most migrant birds have to break their journey south to refuel at favoured stopover sites, the aerial-feeding swallows and martins have the option to feed on the wing as they go. In reality, however, even these birds must break their journeys, searching out sites and habitats rich in flying insects. The birds are feeding over the river this evening because there are good numbers of flies and other insects for them to pluck from the air. The same thing was happening the other night at a friend’s stable, the insects associated with the horses and muck providing rich pickings.
It is at this time of the year that we also see swallows and martins gathering on telegraph wires or fence lines. Others may be seen at favoured roost sites, typically situated over water and within a well-established reed bed. The numbers of birds using these sites often builds up over several nights, although the roost may suddenly break up in response to the unwelcome attentions of the local sparrowhawk or passing hobby, attracted to the roost by the pickings on offer. While the sparrowhawk will remain, the hobby may well follow the martins and swallows, harassing them at other roost sites on the long journey south.
I cast my eyes upward each evening as I wander along the river, seeking out these passing migrants. Just occasionally a late swift joins them, silently feeding alongside and also stocking up reserves for the journey ahead. Some of the swallows may winter as far south as South Africa, the swifts a little further north but where the martins go is a mystery still to be answered.