Swifts

This morning they were merely shadows,
Racing on the curtains, as the day grew bright.
Soundless, black, familiar patterns against light;
Not quite the real thing but just their echoes.
At noon they're screeching out among the sparrows
And the wood pigeons whose great delight
Is randy flapping, clapping, mating, in spite
Of  balancing on fragile saplings. Swallows,
Which are altogether calmer, are, this year,
Noticeable by their absence. Only swifts
Against the shoals of mackerel now appear,
Tiny darts of darkness over drifts
Of fluffy flowers.  Madly they career,
Then vanish where the cloud's in rents and rifts.