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add, Coursers, have a pectinated claw upon the middle toe, and yet do not take insects upon the wing, or even seize their prey with their feet.
It has been ingeniously suggested that perhaps the serrated claw may be used for brushing away the broken wings and other fragments of struggling insects which doubtless adhere occasionally to the basirostral bristles with which the mouth of this bird is furnished. This is very possible; at the same time it may be observed that Hawks, Parrots, and other birds habitually cleanse the bill and sides of the gape with their feet, and yet have no pectination of the middle claw.
A theory advanced by Mr. Sterland,1 and endorsed by Mr. Robert Gray,2 is that since the Nightjar sits lengthwise and not crosswise upon a bough, the serrated claw gives a secure foothold, which in so unusual a position could not be obtained by grasping. But to this theory the objection above made also applies, namely, that many birds, such as Coursers and Thick-knees,
1 "The Birds of Sherwood Forest," p. 172.
have serrated middle claws and yet are never seen to perch.
Some naturalists, and amongst others Bishop Stanley, have surmised that by means of its peculiarly-formed toes, the Nightjar is enabled to carry off its eggs, if disturbed, and place them in a securer spot, but should any such necessity arise, one would think that its large and capacious mouth, as in the case of the Cuckoo, would form the best and safest means of conveyance.
In the young Nightjar at first the peculiarity in question is not observable, and Macgillivray remarked that in a fully-fledged young bird shot early in September, the middle claw had only half the number of serrations which are usually discernible in the adult. He says :— "All birds whose middle claw is serrated have that claw elongated, and furnished with a very thin edge. It therefore appears that the serration is produced by the splitting of the edge of the claw after the bird has used it, but whether in consequence of pressure caused by standing or grasping can only be conjectured." I have detected some confirmation of this in the case of the common Thick-knee, or Stone Curlew, CEdicnemus crepitans, in some specimens of which I have remarked a very distinct serration of the middle claw, in others only the barest indication of it (the edge of the claw being very thin and elongated); in others again no trace of it.
The objections, however, which have been taken to the suggested use of the pectinated claw in the Nightjar, do not invalidate the statements which have been made by Gilbert White and other observers of the bird's movements and habits, for the homologous structure which is found to exist in certain species in no way related to each other, may well be designed for very different functions.
I do not find in the works of either Macgillivray or Yarrell any mention made of the peculiar viscous saliva which is secreted by this bird, and which reminds one of what is observable in the case of the Wryneck and the different species of Woodpecker. It no doubt answers the same purpose, namely, to secure more easily the struggling insects upon which its existence depends.
-■- competent naturalists in different localities, it appears that the usual time of arrival of the Cuckoo in this country is between the 20th and 2 7th of April, and the average date of its appearance may be said to be the 23rd of that month, St. George's Day. In no instance, so far as I am aware, has the bird been heard or seen before the 6th of April. On that date in 1872 it was observed at Torquay, but this was considered by my informant an unusually early date at which to meet with it.
Between April and the end of August, it may be found generally distributed throughout the British Islands, even as far north as Orkney and Shetland. It is also a well-known visitor to the Outer Hebrides. On the European continent it occurs throughout Scandinavia and Russia, and is found in all the countries southward to the Mediterranean, which it crosses in the autumn for the purpose of wintering in North Africa. Eastward it extends through Turkey, Asia Minor, and Persia, to India, and according to Horsfield and Temminck, visits even Java and Japan.1
The Cuckoo does not pair, but is polygamous.
1 The late Mr. Blyth thought that the Cuckoo found in Java by Dr. Horsfield was not the Common Cuckoo of Europe, but an allied race (C. canoroides, Miiller, optatus, Gould), whose range extends eastward at least to China, and southward to Australia. If so, doubtless the same remark applies to Japan. Cf. "The Ibis," 1865, p. 31.