Autumn is the time to fly

Thirty two night herons lift out of the tamarisk at Simar Nature Reserve. They’ve been contact-calling in the dense cover since early afternoon. Now, the conversation takes a business-like turn as they clear the trees and marshal into a flock. Testing the evening air, they circle the reserve and then the valley. They head south over the Wardija ridge but then appear to change their minds. Finally, they gain height, spread out in V formation and head south-west. A few minutes later, I lose them somewhere in the setting red sky.

It’s a sight I see almost every day at this time of year. And yet, it never ceases to move me. I’m not alone. Bird migration has fascinated humans for thousands of years. The ability to cross seas, deserts and continents, and to do so as if guided by an invisible hand and a lust to survive, is pure poetry. Ecologically, it invites superlatives. The number and diversity of birds that fly between Europe and Africa have been described by Matt Merritt as an “extraordinary… enormous… twice-yearly transference of biomass from one hemisphere to another”. For his part, Robert Macfarlane writes of the “strong seasonal compulsions that draw creatures between...