114 BULLETIN 133, UNITED STATES NATIONAL MUSEUM 



HETEROSPIZIAS MERIDIONALIS AUSTRALIS Swann 



Heterospisias meridionalis australis Swann, Auk, vol. 38, 1921, p. 359. 

 (Laguna de Malima, Tucuman, Argentina.) 



Swann recently has separated the southern hawks of this species 

 as above, on the basis of larger size and darker coloration. From the 

 specimens at hand it appears that this action may be sustained on the 

 basis of size, but that constant color differences correlated with geo- 

 graphic range, are not present. Nine specimens of tneridionalis 

 from Panama, Brazil (Para, Pernambuco, Diamantina, and Cha- 

 pada), show the following measurements: Wing, 378^17; tarsus, 

 90-111.5 mm. The series examined contains three females, one 

 doubtful male, and five birds without indication of sex. Three skins 

 from Argentina (Kilometer 182, Formosa, Corrientes, and Conchi- 

 tas, Buenos Aires) measure as follows: Wing, 423-450; tarsus, 109- 

 113 mm. Doctor Allen ^^ has described the plumage changes with 

 age in this species, findings that are verified in the series here at 

 hand. In general, birds during their first season are very dark 

 brown, almost black, save for more or less white on the under surface 

 and some rufous in the primaries and greater coverts. During the 

 second year the amount of rufous in the wings is increased and in- 

 vades more or less of the underwing surface as well as the lesser 

 wing coverts. In the third year the under parts and head become 

 rufous, barred below, save on the throat, with blackish, but the back 

 remains fuscous brown. In the fully adult plumage, apparently in 

 the fourth year, the upper back assumes an ashy shade, but otherwise 

 the bird is similar to what it was in the plumage of the preceding 

 year. Apparently the type of Swann's australis is a bird in third 

 year plumage. I am unable to detect any difference in color between 

 a bird in third-year stage from Para {meridionalis) ^ and one in a 

 similar plumage from near the city of Buenos Aires {australis). 

 An adult female (third year) that I secured on August 12, 1920, near 

 the Riacho Pilaga, Formosa (wing 423 mm.), is somewhat interme- 

 diate between the northern and southern forms, but has been identi- 

 fied with the southern bird. A specimen in the United States Na- 

 tional Museum secured by Capt. T. J. Page at Corrientes (wing 

 448 mm.) seems to be typical australis. As Corrientes is just south 

 of the Paraguayan border it is not improbable that though merid- 

 ionalis was found in the Chaco at Puerto Pinasco, the form of east- 

 ern Paraguay is the larger southern bird, in which case Swann's 

 name will become a synonym of Circus rufulus Vieillot,^^ based on 

 the gavildn acanelado of Azara. 



This handsome hawk was first observed near Las Palmas, Chaco, 

 in July, 1920, but specimens were not secured until I entered the 



wBull. Amer. Mus. Nat. Hist., vol. 5, 1893, pp. 145-146. 

 w Nouv. Diet. Hist. Nat., vol. 4, 1816, p. 466. 



