ELEVENTH ANNUAL, REPORT. 161 
Though some of the smaller species of owls feed largely upon 
insects, there is another nocturnal group of birds which is wholly 
insectivorous. These are the nighthawks and whip-poor-wills 
(Caprimulgidae), and in the noiseless flight, large eyes, and dark, 
mottled plumage we find corresponding resemblances between the 
two groups. Examination of the internal structure shows that 
a real affinity exists, the connection being especially clear through 
the closely-related, fruit-eating, oil-bird (Steatornis), which is the 
sole representative of its Family Steatornithidae. 
There still remains much to be learned from the structure of 
owls, but it is probable that if their line of descent could be re- 
traced, we would find it coalescing sooner with that of the oil- 
bird and the nighthawks, than with any other living groups of 
birds. 
ADAPTATIONS OF PLUMAGE AND BODY. 
Owls are eminently fitted for their i:fe—a nocturnal predatory 
one, and in all parts of their body we find delicate adaptations to 
this end. . Unlike the nocturnal apteryx the sense of smell is 
but slightly developed. In owls, the senses of sight and hearing 
are the only means used to reveal the whereabouts of the prey. 
Taking the plumage as a whole, we find that each feather is 
more or less soft and fluffy especially at the tips of the barbs, 
resulting in a downy condition of the entire outline. The ab- 
sence of barbicels accounts for this, and on many of the body 
feathers we find that even barbules themselves are less numerous 
than on the corresponding feathers of other birds. Even the pri- 
maries or flight-feathers and the tail-feathers, the stiffest and 
strongest on the body, are surprisingly soft to the touch, and at 
first thought this softness would seem to be a great disadvantage 
to the bird in flight. Closer examination of the wing feathers 
of a barred or screech owl shows that, intrinsically, the vanes are 
as impervious to the air as those of a pigeon or hawk. There is 
no radical loss of barbules or barbicels, and hence the feathers 
are perfectly adapted for flight. An interesting condition exists 
however. The barbules along the distal side of each barb are 
greatly elongated, being often six or eight times as long as the 
barbules along the opposite side. Near the base of the barbules, 
the barbicels are as well-developed and numerous as in any bird of 
strong flight, but the elongated distal portions are soft and fluffy, 
and all are bent slightly upward so that they lie on the upper face 
of the vane. Hence the surface of the feather is covered with a 
