BIRDS OF ARGENTINA, PARAGUAY, URUGUAY, AND CHILE 103 



the pampa they did not appear to breed until December. In Uru- 

 guay, where the present bird is common, it is an efficient enemy of 

 the locust hordes that devastate the cultivated lands. 



FALCO FUSGO-CAERULESCENS FUSCO-CAERULESCENS Vieillot 



Falco fusco-caerulescens Vieillot, Nouv. Diet. Hist. Nat., vol. 11, 1817, p. 

 90. (Paraguay.) 



Near the Riacho Pilaga, Formosa, and from that point eastward 

 to the Rio Paraguay, aplomado falcons were fairly common during 

 the middle of August, 1920. They frequented open savannas where 

 stubs of dead quebrachos offered lookout stations, or failing these, 

 even rested on the tops of bushes near the ground. Their flight was 

 swift and direct, performed with strong, quick beats of the wings, 

 and in general appearance they suggested small duck hawks. At 

 the Riacho Pilaga the sight of these little falcons brought conster- 

 nation to the screeching flocks of monk parrakeets that fed in the 

 open in old sweet-potato fields. A male falcon taken on August 12, 

 a bird fully grown but in dark immature dress, had the tip of the 

 bill black, shading posteriorly through gray number 7 to mustard 

 yellow at base, cere and bare skin about eye mustard yellow; iris 

 Rood's brown; tarsus and toes primuiine yellow; claws black. The 

 species was not seen again until April 9, 1921, at Tapia, Tucuman, 

 when a female was brought down with a broken wing as it passed 

 me above a wooded slope. This bird ran sw^iftly on the ground to 

 cover and was captured only after a rapid chase down a brush-grown 

 slope. On April 10 two were seen, evidently hunting, as one dashed 

 down into little openings in the woods and then, disappointed in 

 seeing prey, rose again to continue its direct flight. On April 17 a 

 male was Idlled from a little tree above a mountain pool at an eleva- 

 tion of 2,300 meters, in the Sierra San Xavier, above Tafi Viejo, 

 Tucuman. This was an immature bird of the year, while the female 

 taken at Tapia is probably in its second year, as it is distinctly gray 

 above. 



The subspecies Falco f. septentrionalis Todd^^ proposed for the 

 aplomado falcon of North America may be distinguished by slightly 

 larger bill, longer tail, and bj^ greater average size in all measure- 

 ments. In color northern and southern birds appear identical. The 

 wing measurement in this species seems somewhat variable and in 

 the series at hand is not of definite value in separation, save w^hen 

 used in averages. The bill, however, is slightly larger and longer, 

 and the tail longer in septenti'^ionali^. A single female from La 

 Raya, in the Andes of Peru, that greatly exceeds any other specimens 

 in general size (wing, 313 mm.) save that the bill is small, probably 



s=Proc. Biol. Soc. Washington, vol. 29, June 6, 1916, p. 98. (Fort Huachuca, 

 Arizona.) 



