FAMILY ACCIPITRIDAE 211 



forest at Charco del Toro on the Rio Maje. In early morning 

 scattered Swainson's hawks that appeared to have slept nearby came 

 over the trees in steadily increasing number, until two groups each 

 of a thousand or more were wheeling in circles 500 meters apart. 

 Suddenly the two bands joined immediately overhead, giving me an 

 extraordinary view. As I looked up through the rapidly moving 

 segments of their spirals the air seemed completely crowded with the 

 rapidly turning birds. This continued for 15 minutes until the entire 

 flock moved rapidly to a higher elevation in a favorable air current 

 with which they disappeared. Such flights are the more impressive 

 as there is no sound of calling from any of the birds. 



BUTEO MAGNIROSTRIS (Gmelin): Large-billed Hawk; Cuiscuf 

 Figure 42 

 Falco magntrostris Gmelin, Syst. Nat., vol. 1, pt. 1, 1788, p. 282. (Cayenne.) 



A small hawk with the wing feathers partly rufous, and the fore- 

 neck and upper breast gray. 



Description. — Length 330 to 370 mm. Adult, above brownish gray, 

 darker and grayer on the crown and sides of the head ; upper breast 

 and foreneck gray; throat feathers bordered with white or buffy 

 white to produce streaks ; upper tail coverts buffy white, barred 

 broadly with black ; tail with 4 heavy black bars, the uppermost con- 

 cealed by the upper tail coverts, the light bars rufous, or light gray, 

 according to the race; lower surface white to buffy white, barred 

 heavily with cinnamon brown to buffy brown, the bars edged more 

 or less prominently with gray; under wing coverts white to warm 

 buff, spotted irregularly with cinnamon; primaries and secondaries 

 cinnamon buff to rufous, barred heavily with black, with the tips 

 black ; lower surface of these feathers lighter in color. 



Immature, like adult, but with more or less brown as a wash or 

 streaks in the gray of the upper breast. 



The iris in adult birds is yellow; bare skin above eye and across 

 loral area greenish yellow; bare edge of eyelid honey yellow; cere, 

 gape, and base of mandibular rami dull orange ; a small area on side 

 of maxilla (behind the "tooth," and below the level of the nostril) 

 and central area of mandibular rami dull neutral gray ; rest of bill 

 black ; tarsus and toes light orange yellow ; claws black. (Colors taken 

 from specimens of the race B. m. petulans.) 



This is the most commonly seen hawk of the tropical zone, found 

 mainly in open country, and noted frequently in rows of trees along 

 fences in pastures and cultivated lands and also in more open stands 



