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.Birds of Celebes; Caprimulgidae. 
The Capirmilgidae are again of interest, as Mr. Hartert shows, from the 
high development of protective coloration seen in them. “The colours of the 
Caprimulgidae . . . vary much according to the surroundings, and especially in 
relation to the soil. So, as a rule, we find yellow, buff, and isabelline-coloured 
species in sandy deserts and desert-like localities, darker species in more wooded 
countries, and richly coloured ones in tropical forests. But even the same 
species varies much, according to the soil that it frequents, and therefore several 
species readily form more or less well-defined local races, often well w'orthy of 
subspecific rank. In many cases, of course, as usual, we do not understand 
the reasons why a certain form is differentiated, because we have so little 
knowledge of the influence of climate, the amount of rainfall, the surroundings, 
and the food” (Ibis 1892, 275). 
The need for protective coloration in so defenceless a bird as the Goat- 
sucker which rests on the bough of a tree, or on the ground, in the day-time 
and seeks its insect-food at night, is manifest. Its curious habit, also, of sitting 
along the bough, instead of across it like other birds, is no doubt a protective 
measure. Its plumage of dark brown and grey varied with all sorts of patches, 
spots and vermiculations is admirably adapted to conceal it when lying length- 
ways on a bough covered with lichens, moss, brown bark and the moving sha- 
dows of leaves. So long as it remains thus at rest it is an inconspicuous ob- 
ject; the white outer tail-feathers, wing-band and throat-patch of many species 
of the Caprimidgidae are then hidden by overlying feathers or by its resting-place 
below, but so soon as it takes to wing these white patches must at once become 
striking marks. They exemplify particularly well the “recognition markings” of 
W allace. 
It is a curious fact that the Owls, also nocturnal birds, are on the whole much 
like the Goatsuckers in coloration. In their case, too, protective coloration may 
be reasonably urged to account for the fact, though they are not at all defence- 
less birds hke the Goatsuckers. It is well known how a troop of Sparrows 
delight in mobbing an Owl in the day-time, as indeed also an escaped Parrot, 
Canary, or such like, and for the destruction of Birds of Prey and Crows one 
of the most irresistible lures is an Eagle Owl, which, when seen fastened in 
the open, will have a bad time from the beaks and claws of the diurnal Birds 
of Prey and Crows, if these are not shot down as they come by the hunter 
under cover close by. The plumage of the Owls, likewise resembles that of 
the Goatsuckers in being soft, and their flight is likewise noiseless, a fact ex- 
plained in the case of the Owls by the need they have of approaching their prey 
without being heard. In the case of the Goatsuckers this explanation does not 
suffice — nor indeed does it in the case of the insectivorous Owls. The Goat- 
suckers, as a rule, like their allies the Swifts, catch their insect-prey on the 
wing, but the flight of the Swifts is rushing and loud. 
Quiet flight therefore cannot be of any vital importance; a wide mouth, 
