Pollocobras
Cygnus columbianus malumultra
This monstrosity from northern Mexico used to be the humble tundra swan, until venom from the Serpentfall turned it into a rapacious flying nightmare with the instincts of a locust. While pollocobras are still herbivores, a flock of them can clean out a field of grain within hours — and they spit gobs of poisonous mucus at anyone who interferes with them. Or otherwise annoys pollocobras, which can include simply being in the same county with one.