The Neotropic Cormorant is a smaller sized Cormorant compared to the larger and widespread Double-crested Cormorant. Central Arizona is one of the better places to observe this species in the United States, where they are very common and numerous around ponds and lakes in Maricopa County.
To identify the Neotropic Cormorant, it is noticably smaller than a Double-crested (watch for the two side-by-side in flight). It also had a white "V" around the pointed border of it's bill. (see pictures below)
In the picture below, this shows an adult Neotropic Cormorant (left) with a juvenille (right), side by side. This photograph was taken at Gilbert Water Ranch.