Now for the summer’s showstoppers:
Adam Gretton, Jonny Rankin & Phil Brown
Swift Weather? What were the chances of two megaswifts turning up in the UK within less of a fortnight of each other this June? Slim would probably have been your gut reaction. But you’d be wrong because, counter intuitively, there is good reason to say it is surprisingly likely (leaving aside the fact that it has already happened). In short both species have not only the capability, but also the inclination to undertake such long distance journeys. Born to fly First, and superficially, swifts’ aerodynamics and physique fit them perfectly for an aerial existence. Also, they not only feed exclusively on the wing, but have the capacity to sleep as well, hence their ability to be on the wing all year round. So flying considerable distances is not a problem. Pacific Swift
24
THE HAR R I ER – S e p te mb e r 2 0 1 3
Second, these two species (the Pacific Swift and White-throated Needletail) are actually known for their long-distance flying. Even the Common Swift is reported to undertake mass movements around North European depressions, often entailing a round trip approaching 2000 km, just to feed. Long-distance flight is thus common. Third, in habitat terms the swifts are generalists. Wherever insects occur they can exist and, as a consequence, the swift family is very widely distributed. Fourth, possibly because they can so easily roam, swifts display a proclivity for vagrancy (after all it’s how the family populated so much of the planet), not uncommonly pitching up thousands of kilometres away from their home territory in response to variable insect prey abundances and/ or adverse weather conditions.
