Birdwatch: the invincible swift, effortless master of the air

Also known as devil birds' for their haunting scream, they are just starting to arrive from sub-Saharan Africa

May Day dawns cold and breezy, with sullen grey clouds promising rain. Hope seems very far away. But then, a distant dark streak scythes through the skies over the Avalon Marshes, stiff-winged, direct and determined. A single swift, my first of the year.

As I do every spring, I silently recite the words of the poet Ted Hughes: They've made it again, which means the globe's still working ... "