On Nisus rufitorques and N. poliocephalus

Since my treating of these two species in my work entitled «Muséum d’histoire naturelle des Pays-Bas”, I have had an opportunity of examining a larger series of specimens of them and am now enabled to confirm the results of my former studies. I consider these birds with the allied Nisus iogaster of Amboina and Ceram and a certain number of other species as belonging to a group of Sparrow-hawks, differing from the common sparrow-hawk and its allied species by a greater head, stronger hill, larger eyes, less slender tarsus and especially by shorter but thicker toes, the last characteristic applying more especially to the middle toe.