Apparently the word for a group of swans in the air is a bevy. It's Scottish in origin while Londoners think of a group of swans on the river as a pod. A more exotic one is an exultation of skylarks.
To quote The Daily Mirror's Live Letters page from many years ago:
"Geese flying are a skein and and on the ground they are a gaggle. It's a siege of bitterns, herons or cranes, a chattering of choughs, a herd of curlews, a cast of hawks, a covert of coots - or couts - a team of ducks, a watch of nightingales, a muster of peacocks, a nide of pheasants, a wing of plovers, a clamour of rooks, a spring of teals (small ducks), a flock of swifts and a fall of woodcocks."
And I'm pretty sure it's a murder of crows.
That's all I can manage for now - must fly
Sue