42 BIRDS OF PREY. 
said to, lay four eggs, clouded with reddish. It is common 
also to the north of Europe, if not to Africa. The usual station 
of these birds is on the outskirts of woods, in the neighborhood 
of marshes, — situations suited for supplying them with their 
usual humble prey of frogs, mice, reptiles, and straggling birds, 
for which they patiently watch for hours together, from daybreak 
to late twilight. When prey is perceived, the bird takes a cau- 
tious, slow, circuitous course near the surface, and sweeping over 
the spot where the object of pursuit is lurking, he instantly 
grapples it, and flies off to consume it at leisure. Occasionally 
they feed on crabs and shell-fish, The inclement winters of 
the high northern regions, where they are usually bred, failing 
to afford them food, they are under the necessity of making a 
slow migration towards those countries which are less severe. 
According to Wilson, no less than from twenty to thirty young 
individuals of this species continued regularly to take up their 
winter quarters in the low meadows below Philadelphia. They 
are never observed to soar, and when disturbed, utter a loud, 
squealing note, and only pass from one neighboring tree to 
another. 
The great variation in the plumage of this Hawk has been the 
cause of considerable controversy. Wilson wrote of the black and 
the brown phases as of two species, giving them distinct habits. 
Nuttall, following Audubon, considered the changes from light to 
dark due only to age. Spencer Baird (in 1858), Cassin, and Dr. . 
Brewer agreed with Wilson. Later authorities, however, with 
more material to aid them, have pronounced both views incorrect, 
and have decided that there is but one species, — that the black is 
but a melanistic phase. Our systematists now separate the Ameri- 
can from the Eurcpean form, giving to the former varietal rank, 
as its “trinomial appellation” denotes. 
Nuttall does not mention the occurrence of this bird in Massa- 
chusetts, though Dr. Brewer states that at one time it was abun- 
dant near Boston, and within more recent years numbers have been 
captured by Mr. E. O. Damon on the Holyoke Hills, near Spring- 
field. It occurs within the United States principally as a winter 
visitor, its chief breeding-ground lying in the Labrador and Hudson 
Bay district. 
