NISAETUS PENNATUS. 45 
head. Had the writer of a note to the ^ Field' about the 
nesting of the Osprey at Gibraltar in 1868 or 1869 known 
this, he would not have credited the Ospreys with the nest of 
Bonelli's Eagle. The nest of the former, I may add, is far 
out of view of the signal-station. 
The immature birds of this species are, in their first plu- 
mage, of a uniform rich deep brown colour, which becomes 
lighter with age, as with the young of Aquila adalberti. 
The tarsus, feathered to the feet, is very long for the size 
of the bird, the thigh being still longer in proportion. 
The cere and feet are pale yellow ; the bill yellow, with a 
bluish-black tip ; the irides golden yellow. A freshly killed 
female measured 27 inches in length, the wings from tip to 
tip across being exactly 5 feet, wing from carpus to tip 25 
inches, tarsus 4i inches. I never heard any good distinctive 
local name for Bonelli''s Eagle ; perhaps the best is " el aguila 
de las rocas.'" 
19. NisAETUs PENNATUS (Gm.) . Booted Eagle. 
Moorish. Ta-ferma {Favier). 
" This Eagle is migratory, crossing to Europe in March and 
April, returning in September ; some remain to breed in the 
vicinity of Tangier to go south for the winter with the return 
migration. They nest on high trees in April and May, laying 
from one to three white eggs, often much stained and with a 
rough surface. It is abundant when on passage. '^ — Favier. 
On the Spanish side this, the smallest of the European 
Eagles, is, about Gibraltar, entirely migratory. I noticed 
many crossing on the 24th of March. It frequents wooded 
districts, and is the most plentiful of the birds of prey in the 
cork-wood during the summer, when their wailing cry may 
be heard all day long. The nests there that I saw were, 
without exception, on oak trees, sometimes completely hidden 
in ivy. In the Cotos near Seville they generally build in 
pine trees. The same nest is used year after year ; if the old 
birds be shot, next season another pair take possession to 
repair and reline it with fresh green twigs of the oak. Two is 
the usual number of eggs ; I have known three, but frequently 
