78 FALCONIDZ. 
by their rufous tail-bands. On the other hand, Mexican examples have grey tail- 
bands, and appear at first sight to be distinct ; hence Prof. Ridgway has separated the 
northern birds as Rupornis griseicauda, and those from Cozumel, which also have 
grey tails, as BR. gracilis. 
We cannot admit the specific distinctness of R. ruficauda and h. griseicauda, for in 
Costa Rica, Nicaragua, and Guatemala we find a perfect intergradation between these 
two forms, some specimens having rufous tails suffused with grey, while others have grey 
tails suffused with rufous. 2. gracilis is aslightly smaller race of the Mexican #. grisei- 
cauda, but Cozumel birds are matched by others from Yucatan and Southern Mexico. 
The measurements taken from our large series prove that no reliance can be placed 
on differences of dimension. Asa rule, the sexes attain an equal length of wing. The 
males of R. ruficauda from various parts of Central America vary in this respect from 
8-1 to 9°4 inches, while the females vary from 8°6 to 9°6 inches. The wing of the 
grey-tailed Mexican race measures from 8°8 to 9°8 inches in the male, and from 8:9 to 
9-9 in the female; that of the Cozumel bird from 7°9 to 9°2 inches, while Bonacca 
specimens reach to 9°5 inches. Thus it will be seen that, although the smallest male 
bird we possess is from Cozumel, there are many others from the same island which 
equal the dimensions of those from the mainland, and as our series shows every possible 
gradation in size, we have not felt justified in separating them specifically. 
Young birds are undoubtedly darker than the adults, and show less rufous on the 
wings. The tail-bands in immature specimens are six in number, whereas old birds 
have only four or five light ones. 
As will be seen by the list of localities given above, there is scarcely a part of Central 
America in which R. ruficauda does not occur, and from the dates attached to our 
series of specimens it is apparently a resident throughout our region. In Mexico 
Sumichrast *° states that it is found on both coasts, up to an elevation of 1200 metres, 
where it is abundant. Mr. Witmer Stone says that in Yucatan it was the commonest 
Hawk in the neighbourhood of Izamal *4. 
In Guatemala it abounds in the hot coast-region, and is probably the most abundant 
of the Accipitres. We obtained specimens from the plains of Zacapa, the Pacific 
coast-region, the valley of the River Polochic, Choctum, in the forest-region of Vera 
Paz, and the district of Peten!®. In Nicaragua f. ruficauda is abundant, according to 
Mr. Nutting 28, who also found examples in the Gulf of Nicoya, in Costa Rica, where 
it is the commonest Hawk of the country ?’. 
Although widely distributed, this species is not found in the high mountain districts, 
but it frequents the lowland plains up to an elevation of about 2500 feet. Its food in 
Guatemala consisted chiefly of snakes and lizards, though we have also found locusts 
and centipedes in its stomach °1°, In Costa Rica, Mr. Nutting says that it prefers open 
woods, although it also occurs in the thickest forests 2° 7%. 
The nest and eggs have not been discovered. 
