STUDIES OF THE AMERICAN FALCONIDJE. 
By Robert Ridgway. 
Genus NISUS, Cuvier. 
INTRODUCTION. 
The latest authority on the birds of the family to which the genus 
Xisus belongs (the “Catalogue of the Accipitres, or Diurnal Birds of 
Prey, in the Collection of the British Museum ”, by Mr. B. Bowdler 
Sharpe*) allows eleven American species which we consider as belong> 
ing to this genus as properly restricted, they being included in that work 
in the genus “ Accipiter .” The species recoguized by Mr. Sharpe are 
the following 
(1.) “ 2. Accipiter fuscus.” (p. 135.) 
(2.) “ 3. Accipiter cooperi.” (p. 137.) 
(3.) “ 4. Accipitef tinus.” (p. 139.) 
(4.) “ 8. Accipiter collaris.” (p. 144.) 
(5.) “13. Accipiter erythrocnemis.” (p. 147.) 
(6.) “ 14. Accipiter chionogaster.” (p. 148.) 
(7.) “ 16. Accipiter ventralis.” (p. 149.) 
(8.) “ 19. Accipiter guttatus.” (p. 152.) 
(9.) “20. Accipiter pileatus.” (p. 153.) 
(10.) “21. Accipiter bicolor.” (p. 154.) 
(11.)* “ 22. Accipiter cliilensis.” (p. 155.) 
Besides the above, two species which are probably closely allied to 
this group, are given, but it seems to us erroneously, under the genus 
Astur, these being the Falco poliogaster of Temminck and the Astur pec- 
toralis of Bonaparte. These two remarkable and rare species we have 
had no opportunity to examine, in order to verify the propriety of in¬ 
cluding them in the genus Astur , but the probability is very strong that 
they will prove subgenerically, if not generically, distinct from the typi¬ 
cal members of that genus. 
To aid us in the study of this difficult group, we have had access 
to the collections of the principal museums of the United States; the 
National museum, at Washington, the collection of the Philadelphia 
Academy of Natural Sciences, the American Museum at Central Park in 
New York City, the museum of the Boston Society of Natural Ilistory, 
and the Museum of Comparative Zoology at Cambridge, Mass., furnish¬ 
ing the bulk of the material. Two species not known to exist in any 
American museum were furnished for examination by Mr. Osbert Salvin, 
of England, who kindly loaned his large and elegant series of these birds 
for the purpose ; the unique type of another was obtained from the mu¬ 
seum of Yassar College, Poughkeepsie, N. Y., through the courtesy of 
Professor James Orton, its collector; and Mr. George N. Lawrence, of 
* Loudon, 1874, 8vo., pp. 479, pis. xiv. 
