Buzzard is a colloquial term and is not very rigidly defined. It includes pretty much any vulture (as well as hawks) as it is commonly used in America.Besides, buzzard is the name for a Eurasian hawk, a bit smaller than a red-tailed hawk. Vultures are NOT "buzzards"...
http://www.m-w.com/dictionary/buzzard
http://en.wikipedia.org/wiki/Buzzard
If they can get to a newborn before the mother recovers, they will begin feeding on the calf starting with the eyes and going in at the rear end. They may not kill it outright, but there's not much else to do with a calf that's gotten this treatment but put it down.I won't even ask how it kills a calf!