Laudator Temporis Acti

Aeschylus, fragment 275 Nauck, lines 1-2 (tr. Herbert Weir Smyth):

For a heron, in its flight on high, shall smite thee with its dung, its belly's emptyings.

ἐρῳδιὸς γὰρ ὑψόθεν ποτώμενος
ὄνθῳ σε πλήξει νηδύος κενώμασιν.

James Hancock and James Kushlan, Herons (Oxford: Oxford University Press, 2005), p. 217 (on the green heron, Butorides virescens):

It is often seen flying after being disturbed. Then it flies with head out and feet dangling and gives the characteristic 'Skeow' call. It also relieves itself upon taking off, leading to some vulgar common names.

For the vulgar common names, see John Eastman, Birds of Lake, Pond, and Marsh: Water and Wetland Birds of Eastern North America (Mechanicsburg: Stackpole Books, 1999), p. 204 (also on the green heron):

Flying away from disturbance, this heron often lets loose a stream of white defecation, hence the vernacular labels "shitepoke" and "chalkline."

See also Scott Weidensaul, Of a Feather: A Brief History of American Birding (Orlando: Houghton Mifflin Harcourt, 2007), p. 72 (on the "welter of colloquial English names that grew up in different regions, sometimes varying from valley to valley"):

Flush a bittern or a heron, and it'll usually void a stream of excrement as it takes off; such birds were known as "shitepokes" in polite company, but the middle e vanished when the audience was rougher.

In 2006 my son went camping with friends in a swamp in eastern North Carolina. His account of the trip included this anecdote:

On our midnight canoe run, Ken and I disturbed a great blue heron nesting in the canopy above us: as it flew away, loudly protesting, it discharged its copious cloacal contents in our direction, which splashed loudly around the canoe nearly hitting us. I shone the light upwards through the canopy and I remember quite clearly the sight of the fecal salvo descending rapidly towards us.