74 MR. J. H. GURNEY, JUN., ON THE NIGHTJAR. 
one; and Mr. Gray has seen them cleverly picking the Otter 
Moth off stems in grass-fields.'"' 
In most works on ornithology it is stated that the bristles t 
on the Nightjar's hill are to help it in catching moths ; but a 
careful consideration of the matter will convince any one that this 
agile and wide-mouthed bird wants no such assistance. There 
is another and more probable use for which they are intended, 
and that is for assisting in the utterance of its familiar note. It 
seems highly probable that the prolonged jarring sound is, in part, 
due to the bristles, which are, doubtless, movable ; and, in con- 
firmation of this theory, we find that certain American Nightjars, 
of the genus Cliordeiles or Cliordediles, which have no bristles, 
make no jarring. Gilbert White observed that the under mandible 
quivered in the act of jarring, and this must help to produce the 
sound ; and it is said that the head is always held lower than the 
body, which may further assist it. 
Whatever may have been said to the contrary, it is an indubitable 
fact that the Nightjar only jarrs when at rest. It is very drowsy 
before sundown, but at night it sounds clear and loud, like the 
croaking of frogs. It may occasionally be heard jarring long- 
before sundown ; and now and then a feeble jarring may be 
caught as early as four p.m., and it will go on to as late as eight 
in the morning. 
Eobert Marsham of Stratton Strawless in Norfolk, writing in 
1781, says : — “I counted 1150 whilst a Dawliauk sung, and I am 
confident that + fifty might have been counted before I began to 
tell ” (Trans. Norfolk and Norwich Nat. Soc. vol. ii. p. 33). In 
1872, Mr. John Cordeaux, in company with the writer, timed the 
duration of a Nightjar’s jarring, and made it eighty seconds, and 
* Many other instances might be quoted, but the following note in the 
‘ Zoologist ’ by Mr. G. B. Corbin will give a good idea of what the Nightjar’s 
customary food is : — Having shot a pair in Hampshire, he proceeded the 
next day to shin them, when, on cutting open their crops for examination, 
out flew two Moths, while several others crawled out after twenty-four hours’ 
confinement, viz., eleven Antler Moths, one Yellow Underwing, three 
C. selaselhis, five C. culmellus, three common Beetles {G. stercorarius ) . 
f The long stiff bristles appear very early, as does the serrated middle 
claw, the use of which has been so much debated ; but the bristles 
appear first. 
