After a summer of prolonged dry hot spells, the telegraph wires are laden with chattering hirundines: Swallows and House Martins enjoying the last days of summer before the gradual but inevitable seasonal change. That change brings us shorter hours of daylight, lower temperatures and more variable weather patterns: all triggers to the Swallow and Martin families that a better experience lies elsewhere, after a long and arduous journey or migration which will bring these birds south to the African continent for the winter months.
I certainly get the impression that the move south is on or coming soon. Traditionally I think of the third week of September as a period of very large passage, with steady streams of birds coasting it in low, direct flight, with no deviation from this, no doubt to protect energy levels. Right now, birds are gathering on wires, twittering information amongst their kind, and taking short ‘test’ journeys and searching out safe communal roosts, away from the nest sites of summer, where home was a mud nest on a house eave or concealed on a shelf in a farm building.
Swallows migrate by day and can break their journey, to drink or feed as they need; they often congregate in favoured coastal lakes and headlands before taking flight over open seas, using the shortest possible route away from safe coasts and timing their departure to coincide with a tail wind or ahead of a weather front. Regardless of how skilled they are as migrants; harsh weather can disorientate them and by contrast more desert like conditions will be endured at the African end of the long journey. Small wonder then that Swallows rere up to three broods of five young in a decent Irish summer, just like the one we have had: they need the numbers to cover mortalities along the way. The long journey south can take place over the period September to December, with the welcome in Southern Africa just as important in that hemisphere as it is to us, Swallows and House Martins, harbingers of summer, twice in one year.