Review 14

Putting the sections of No 14’s migration journey together into one map is always fascinating and always begs the question, ‘Why do they do it?’ The simple answer is, of course, for food. Swallows and other small migrants take advantage of the burst of Northern insects hatching out in their myriads in the Spring. Anyone taking a late stroll around Bassenthwaite must have been aware of the clouds of midges glowing like back-lit ballerinas dancing their short lives away in the setting sun. Similarly ospreys home in on the supplies of fish rising in the warming waters. 10,000 years ago when ice still held much of Europe in its grip ospreys must have been largely confined to the Tropics. As the ice receded young birds would have pushed out across the Sahara, as it developed into a much damper place supporting trees and grassland rather than today’s searing waste. By the time the desert came into being the migration was already established and so they continue to this day. But how the instinct or physiological mechanisms to support this global journey developed we still have very little idea.