322 THE ZOOLOGIST. 
bristles below. The bird appears to be a vegetable-feeder, and is 
almost noiseless, uttering very rarely a harsh double note. 
The Owls (Strigide) present some strange modifications, 
and prominently display the fact that organs, by almost 
insensible gradation of structural change, are equally adapted 
for use by daylight, semi-darkness, and night. Only intensity 
of sensory power is secured where absence of light is essential 
to their well-being. What more applicable to noiseless flight 
than their fluffy feathers, whose lightness is strengthened by 
additional serrated delicate barbules interlocking and giving. 
the gossamer framework efficacy for nocturnal purposes? Their 
great cnriously-set eyes, with enormously broad iris and other 
anatomical attributes, so dazed in the sun’s glare, light up and 
receive every faint ray of night reflection; their auditory 
apparatus, with great open tympanum, downy plumage, and 
circlet of feathers, in substitution for an auricle, guiding and 
concentrating sound, however faint, to the recessses of an ear 
specially constructed as a receptacle fur appreciation of vibratory 
movement. ‘The facial disc, the peculiarities of cere and nostrils, 
the beak and talons, all betoken adaptive power as aérial night- 
hunters. 
The Nightjars (Caprimulgide) are equally creatures of night ; 
but, unlike the Owls, their enormous gaping mouth, defended 
by stiff bristles, is an adaptation implying hunting and securing 
prey on the wing. Swallows of the night, the Goatsuckers 
possess a plumage vieing with the Owls in soft delicacy and 
lightness. The eye equally and specially conforms to the 
principles necessitating vision in the uncertain haze of twilight 
and night. The diminutive weak legs present no characters of 
a percher, and the bark-like plumage of the bird, when resting 
and cowering on boughs, protects it from its diurnal enemies. 
It has a peculiar pectinated claw on the middle toe, which may 
either facilitate its balance on a bough or be used as a cleansing 
tool when broken moths’-wings stick around the gape. No 
nocturnal beetle or sphinx moth, however powerful on the wing, 
is safe from the noiseless circling sweep or rapid dash of “the 
awaken’d Churn-owl.” 
Many other birds besides the foregoing are nocturnal; but 
these illustrate sufficiently how sensory organs are correlated 
with crepuscular habit. 
