Flock in Wikipedia

Flock. - The flocks of Israel include generally both sheep and goats: "The sheep eat only the fine herbage, whereas the goats browse on what the sheep refuse. They pasture and travel together in parallel columns, but seldom intermingle more closely, and at night they always classify themselves. The goats are for the most part black, the sheep white, dappled or piebald, forming a very marked contrast..." (Tristram). The shepherd usually leads the flock, calling the sheep by their names from time to time; in his footsteps follows an old he-goat, whose stately bearing affords to the natives matter for several comparisons; the Arabs, indeed to this day, call a man of stately mien a "he-goat". The shepherd at sunset waters his flock, folds them ordinarily in some of the many caves found on every hillside, and with trained dogs guards them at night.

Link: https://en.wikipedia.org/wiki/Herd