After a reasonable summer, the telegraph wires are beginning to fill up with chattering Swallows and Martins: I certainly get the impression that the move south is on, or coming soon. Apart from the communal exchange of information, Swallows and House Martins are enjoying the last days of summer before the gradual but inevitable seasonal change. Traditionally I think of the second or third week of September as a peak period of migration. Shorter hours of daylight, lower temperatures and more variable weather patterns are all triggers to the Swallow and Martin families that a better experience lies elsewhere. After a long and arduous journey or migration, these birds arrive on the African continent for the winter.
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 land 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 raise up to three broods of five young in a very good Irish summer: 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 are harbingers of summer, twice in any one year.
