272 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 150 



or three eggs have the white ground color nearly or wholly con- 

 cealed by a wash of warm brown, mingled with blotches, irregular 

 spots, and lines of chestnut and darker shades of brown. There is 

 much variation in marking, and occasionally eggs are merely lightly 

 spotted, or, rarely, nearly plain. At first view of a series the 

 variation is so great as to give the impression that several species 

 must be represented. Bent (U. S. Nat. Mus. Bull. 170, 1938, p. 

 130) gives the average size as 59.4x46.5 mm. (taken principally 

 from eggs collected in Texas and Florida) . 



The rattling, clattering call of these birds, almost mechanical in 

 its sound, is heard mainly in the nesting season. 



Near Pacora, caranchos are called guaraguo, a name that applies 

 properly to the red-tailed hawk. 



Caracaras are found from Baja California, southern Arizona, New 

 Mexico, Texas, Florida, and Cuba, south throughout the Americas 

 to Tierra del Fuego and the Falkland Islands. South to northern 

 Brazil the back and rump are plain blackish brown to black, and the 

 upper tail coverts also are plain or lightly barred at the side. From 

 south of the Amazon River southward the back, rump, and upper 

 tail coverts are barred with grayish white. The difference described 

 is definite but is one of degree, and the birds throughout agree in 

 form, habits, and voice. Though the two styles have long been re- 

 garded as separate species, the present-day tendency to unite them as 

 one is here accepted. The two intergrade in Brazil in the area im- 

 mediately south of the Amazon River. 



Two subspecies, slightly different in depth of color, are found in 

 Panama. 



The generic name Caracara used here follows acceptance of this 

 name in the last edition of the A.O.U. Check-list of North American 

 Birds (1957, p. 116). Polyborus proposed in 1816 by Vieillot (Anal. 

 Nouv. Orn. filem., p. 22) with "Caracara, Buff.," which is Falco 

 brasiliensis Gmelin, as its only species and therefore its type, was long 

 the accepted genus for the caracaras. Buffon's name "Caracara" is 

 based on a bird described by Marcgrave in his Historia Natural do 

 Brasil published in 1648, with an illustration in the stilted form com- 

 mon in works on natural history of that period. In a study of the 

 original paintings from which the figure was reproduced Adolf 

 Schneider (Journ. Orn., 1938, pp. 93-94, fig. 3) found that the 

 Caracara of Marcgrave actually is the harrier known currently as 

 Circus buffoni (Gmelin). The generic name Polyborus, 1816, thus 

 becomes a synonym of Circus Lacepede, 1799. The next available 

 name for the group formerly called Polyborus is Caracara Merrem (in 



