Armies gathering now
as the huge flocks on flocks of winging birds, geese or cranes
or swans with their long lancing necks – circling Asian marshes
round the Cayster outflow, wheeling in all directions,
glorying in their wings – keep on landing, advancing,
wave on shrieking wave and the tidal flats resound.
So tribe on tribe, pouring out of the ships and shelters,
marched across the Scamander plain and the earth shook,
tremendous thunder from under trampling men and horses
drawing into position down the Scamander meadow flats
breaking into flower – men by the thousands, numberless
as the leaves and spears that flower forth in spring.

– Homer

The Iliad, Book 2, lines 543-554. As the Achaean soldiers mass for war, Homer’s extended simile likens them to huge flocks of great flying birds, wheeling in all directions and glorying in their wings.