What is a Common Welsh Green?

Newt Scamander's description of a Welsh Green dragon from the Fantastic Beasts book

The Welsh Green blends well with the lush grass of its homeland, though it nests in the higher mountains, where a reservation has been established for its preservation. The Ilfracombe Incident notwithstanding, this breed is among the least troublesome of the dragons, preferring, like the Opaleye, to prey on sheep and actively avoiding humans unless provoked. The Welsh Green has an easily recognisable and surprisingly melodious roar. Fire is issued in thin jets. The Welsh Green’s eggs are an earthy brown, flecked with green.

Fantastic Beasts and Where to Find Them

By J.K. Rowling