276 THE Witson BULLETIN—NOos. 76-77. 
before eating. On the 40th day it learned to spring from my 
hand to sieze its prey in its beak before placing it under its 
talons. Could fly wel! and began to long for liberty. One week 
later it beat against the window. It learned to eye its feeding 
board whenever I appeared, and a stranger so fiercely as to 
have the appearance of about to attack him; and for the first 
time used its left foot in striking its victims. It was not until 
it was 89 days old that it uttered its first “rusty hinge” whis- 
tle, the adult and harsher cry than the juvenile. 
Moult and Renewal. 
Much to my surprise I could discover absolutely no litera- 
ture on the subject except the following eight words from 
Maynard: “Like most hawks, these birds moult in August.” 
Of the closely related Swainson’s Hawk, Dr. Coues writes: 
“A moult occurs in August and September; it is protracted, 
the feathers being very gradually renewed, almost one by one; 
the fresh heavily colored feathers contrasting strongly with the 
ragged and faded ones worn during the summer. The young 
have no moult at this season. I have no observations upon a 
spring moult, which probably occurs in both old and young.” 
Newton intimates that Diurnal Birds-of-Prey generally moult 
in mid-winter or even later. Under the title of “Observations 
on the Color Changes in the Genus Buteo, Apparently Due to 
Aptosochromatism” (cf. Bul. Hadley Climatological Labora- 
tory University, New Mexico, U1, 7, July, 1903, 1-14) the late 
Frances J. Birtwell gave the results of the examination of an 
adult and juvenile Buteo swainsom on Dec. 7 and May 6, and 
an adult Buteo borealis calurus on Dec. 7, and April 1, con- 
fined in a basement during the winter, to prove color change 
without moult. Unfortunately May 30 witnessed the only 
collection of moulted feathers and the search for new growth 
on the birds at the time of skinning. 
Plucked of feathers the adult is found completely covered 
with a heavy coat of down, even to the tips of the wing bones 
and heel joints; white, except a dusky streak along the wing 
bones at the insertion of the greater coverts. 
