Swifts -- "the globe's still working"

There is a famous poem by Ted Hughes about the return to the UK from Africa of the swift with this extract:

"They’ve made it again,
Which means the globe’s still working, the Creation’s
Still waking refreshed, our summer’s
Still all to come —
And here they are, here they are again
Erupting across yard stones
Shrapnel-scatter terror. Frog-gapers,
Speedway goggles, international mobsters —

A bolas of three or four wire screams
Jockeying across each other
On their switchback wheel of death."

The return of the swift at the end of April is a highlight of my year: each spring the screaming overhead of this scythe-winged bird signals the return of  warm summer days and reminds me (and Ted Hughes) that the world is still working as it should. There is a danger this may not be for ever though: there are plenty of hazards on the migration paths of summer visitors and many bird species are suffering great reductions in numbers e.g. cuckoo and house martin.