Watch What Happens to This Tree

This was filmed in Zaandam, Netherlands.

These are almost certainly Starlings. What, exactly, should we call such a massive flock?

After all, almost every other group of animals has a poetic phrase attached to it.

• It's a paddle of ducks and a flock of seagulls.
• It's a skulk of foxes and a cry of hounds.
• It's a lamentation of swans and a charm of hummingbirds.
• It's an unkindness of ravens and a murder of crows.
• It's a mob of kangaroos and a pride of lions.
• It's a school of fish and a pod of whales.
• It's an aerie of eagles and a wake of buzzards.
• It's a flight of cormorants and a mob of emus.
• It's a mischief of rats and a clutter of cats.
• It's a charm of finches and a hedge of herons.
• It's a husk of hares and a trip of goats.
• It's a band of gorillas and a troop of monkeys.
• It's a deceit of lapwings and an ascension of meadow larks.
• It's a burden of mules and a drove of ox.
• It's a descent of woodpeckers and a kettle of hawks.
• It's an ambush of tigers and a gang of weasels.
• It's a bale of turtles and a knot of toads.
• It's a dray of squirrels and a surfeit of skunks.
• It's a business of ferrets and an array of hedgehogs.
• It's a rookery of albatrosses and a tiding of magpies.
• It's a coalition of cheetahs and a leap of leopards.
• It's a route of coyotes and a packs of wolves.
• It's a cast of merlins and a scold of blue jays.
• It's a ridicule of mockingbirds and an ostentation of peacocks.
• It's a labor of moles and a richness of martens.
• It's a raft of pelicans and a covey of pheasants.
• It's a bloat of hippopotamus a crash of rhinoceros.
• It's a cackle of hyenas and a shiver of sharks.
• It's a flight of pigeons and a wing of plovers.
• It's a clan of badgers and a nursery of raccoons.
• It's a cloud of flies and a swarm of bees.
• It's a circus of puffins and a flush of quail.
• It's a regiment of flamingos and a huddle of penguins.
• It's a sounder of boar and an army of frogs.
• It's a congregation of plovers and a walk of snipes.
• It's an intrusion of cockroaches and smack of jellyfish.
• It's a piteousness of doves and an exaltation of larks.
  

So what is a huge group of Starlings called?

I would propose a vulgarity of starlings -- a term lifted wholecloth from their Latin name -- Sturnus vulgaris. 

Of course, we could also call it a constellation of starlings, working off of their more common name, which references the spotted iridescence of their summer plumage.