 The eight living pelican species were traditionally divided into two groups , one containing four ground @-@ nesters with mainly white adult plumage ( Australian , Dalmatian , great white , and American white pelicans ) , and one containing four grey or brown plumaged species which nest preferentially either in trees ( pink @-@ backed , spot @-@ billed and brown pelicans ) , or on sea rocks ( Peruvian pelican ) . The largely marine brown and Peruvian pelicans , formerly considered conspecific , are sometimes separated from the others by placement in the subgenus Leptopelicanus but in fact species with both sorts of appearance and nesting behavior are found in either . 
