Mike gave you an excellent answer about 'cuervo",it refers to raven (it is twice as large), and crow.

Bears do have distinguishable names,= oso n e g r o, panda, oso polar, etc.

Yeah you're right, both crow and raven are from the Corvus genus, and that's the latin that el cuervo comes from (cuervo<corvo<corvus(lat.)

Looks like el cuervo común covers ravens just because it appears that most ravens are the so-called "common raven". But it looks like there's no "common crow". North America has its Corvus Brachyrhynchos but there are other kinds that are considered just as important I guess (see link), such that there aren't Spanish names for each one.

So I guess you'd have to resort to the latin to clarify the N.American crow (for example): el cuervo (C.brachyrhynchos)