The dry Southeast grasslands of Arizona are home to both the Common Raven and the Chihuahuan Raven.
The Common Raven is distinguished from the Chihuahuan Raven by habitat, larger size, longer bill, shorter nasal bristles (feathers coming down across the culmen) and voice (Chihuahuan Raven's call is higher pitched and sounds more like a mallard call).
The two raven species should be distinguished with great care in areas of range overlap, such as in Texas, Arizona and New Mexico.
The often mentioned white-based neck feathers of Chihuahuan can be hard to see, but this can be a good field mark if the wind is blowing the right way!

Patagonia, Arizona, USA, 1 May 2008