But restless hurry through the busy air,
Beat by unnumbered wings. The swallow sweeps
The slimy pool, to build the hanging house
Intent. And often, from the careless back
Of herds and flocks, a thousand tugging bills
Pluck hair and wool; and oft, when unobserved,
Steal from the barn a straw, till soft and warm,
Clean and complete, their habitation grows.
Another celebrated poet completes the picture: —
The cavern-loving wren sequestered seeks