Closely connected with the above parasitic habit is the question of the colour of the egg. Red or blue specimens have undoubtedly been found in Germany and elsewhere, as well as the typical brown or greyish varieties; but they do not always assimilate to those of the foster-parent, albeit to the eggs of Pipits, Wagtails, and so forth, that of a Cuckoo is often exactly similar. The theories advanced to account for this are by no means conclusive, though hereditary habit may afford a clue; we may, however, be sure that the hen cannot determine the colour of her egg.
With us the most usual foster-parents are the Meadow-Pipit, Pied Wagtail, Reed Warbler, Hedge-Sparrow and Robin, perhaps in the above order. They seldom, if ever, seem to resent the intrusion, or to notice their consequent losses. The careful observations of Jenner, Hancock, and Mrs. Blackburn shew that the young Cuckoo, when some thirty hours old, begins unaided to remove from the nest the rightful progeny or unhatched eggs by means of its broad back, which has a central depression for the first twelve days; but after this hollow is filled up the desire is said to cease. It pushes below a nestling with its wings, and raises it with much exertion to the edge of the nest, finally ejecting it by a supreme effort.
The probable reason why the Cuckoo's egg often hatches first is the hen's habit of selecting nests with only one or two fresh eggs. Subsequently she neglects her offspring entirely. It is stated that the males, who alone utter the well-known notes, decidedly outnumber the females, and that no strict pairing takes place; while in the courting season a curious bubbling sound, attributed to the hen, may be heard as two or three individuals chase each other along the hedgerows. Wooded districts and bare hill-moors are equally frequented, trees being constantly used as perches. The quick, straight flight is varied by twists and swoops; the food consists of insects and their larvae, the stomach often becoming lined with hairs of caterpillars. Our Cuckoo does not eat eggs, but various foreign species add to their diet seeds and other fruits, land-molluscs, worms, frogs, lizards, small snakes, birds, and mice. Chalcococcyx lucidus bruises its food before swallowing it.
The genus Coccystes, of South Europe, Africa, and Tropical Asia, includes the Great Spotted Cuckoo (C. glandarius), which has twice occurred in Britain, a crested greyish-brown bird, with a yellowish throat, white under parts and markings above. In Southern Spain and Northern Africa it deposits from two to four eggs in the nests of the Magpies, Pica rustica, P. mauritanica, and Cyanopica cooki, or of the Grey Crow, Corvus cornix; these eggs, like those of the foster parents, being pale green with brown and lilac markings. The note of the male is "kee-ou, kee-ou" or "kark-kark", of the female "burroo-burroo." C. coromandus, chiefly greenish- and bluish-black above with rufous wings and white nuchal collar, and buff below with grey abdomen, ranges from India and Ceylon to China and Celebes, laying roundish, plain green-blue eggs in nests of Crateropus and other birds, and having a true Cuckoo's note. C. serratus of South Africa, which is greenish-black with a white alar band, is somewhat terrestrial, and lays a white egg in nests of Pycnonotus and Sigelus.
Surniculus lugubris, extending from India to China and the Malay Islands, is black, with green and purple reflexions and a few scattered white markings. The tail is sometimes forked. Cacomantis passerinus, of India, Java, and Sumatra, is grey, having an olive gloss above, blue-black rectrices with white bars, and white abdomen. It frequents jungles, utters a plaintive series of whistles, continuing for hours, and lays bluish eggs with purplish, markings in various birds' nests. C. virescens of Celebes and Bouru is said by Dr. Meyer to build its own nest. Chrysococcyx smaragdineus, of Tropical and Southern Africa, is a lovely emerald-green bird, with yellow breast and white-barred lateral rectrices. The female has a partially rufous head and mantle, coppery, bronze, and green upper parts, and white lower surface banded with green. The males whistle loudly to their mates for long periods, perched on tall trees, or hawk for insects in the air. C. cupreus, of the same countries, is in both sexes coppery-green varied with white above, and white with bronzy bars below; it is called "Di-dric" from its cry, and lays white eggs in Sun-birds' and Finches' nests. The similarly coloured Chalcococcyx lucidus of Australia, New Zealand, and the Chatham Islands has a reiterated plaintive note, with the effect of ventriloquism, and foists its greenish-white eggs with brown spots upon Acanthiza and Gerygone.
Of Eudynamis, ranging from India and Ceylon to Australia and Polynesia, the black males are barely distinguishable, but the females vary, and are black, brown, rufous, and white. E. honorata, the noisy Indian Koël, has a loud melodious or hoarse whistling note, supposed to portend rain; it feeds on fruit, and lays from one to four greenish eggs with brown and grey blotches in nests of Crows. E. melanorhyncha is the "foreteller at night" of Celebes.[[216]] The extraordinary Scythrops novae hollandiae, or Channel-bill, of Australia, Papuasia, and the Moluccas, has a grey head, brownish back, and whitish under parts with indistinct dusky bars, the tail exhibiting a subterminal blackish and a terminal white band. The large maxilla has two lateral grooves, the bare lores and orbits are scarlet. This big bird flies like a Hawk, and is possibly parasitic; while eggs, taken from the oviduct, are white with pinkish-brown spots. The weird cry or shriek is syllabled krok, and the flocks feed on fruits and insects.
Coccyzus americanus, the Yellow-billed Cuckoo of America, has occurred in Britain, and ranges from the Great Plains, Canada, and New Brunswick to Argentina; it is an arboreal species, pairing and building–apparently twice a year–a slight flat nest of twigs, grass, and moss, lined with leaves. It lays from three to five light greenish eggs, and the hen feigns lameness when danger threatens the young. C. occidentalis is a more western form. C. erythrophthalmus, the American Black-billed Cuckoo, has been killed in Ireland and Italy. The coloration in the eight members of this genus is brownish-grey, relieved by rufous, the under parts being buff or white.
Sub-fam. 2. Centropodinae.–This group comprises only the thirty or more large Coucals (Centropus) of the Ethiopian Region, Egypt, Madagascar, India, and the countries thence to China, Papuasia, and Australia. C. sinensis, the Crow-Pheasant, extending from India and Ceylon to China, is black with purple and green reflexions, the mantle being chestnut; C. unirufus of the Philippines is entirely rufous. They are strong-billed, long-legged birds with terrestrial tendencies, noisy yet often shy, which fly heavily, run, climb, leap, or glide with up-turned tail about the trees in forests and jungles, and utter a mellow "hoo-too" or a chuckle. The food consists of insects and their larvae, molluscs, reptiles, small mammals, and nestling birds. They make a large globular nest of twigs and leaves, or even of rushes, grass, and rags, with a lateral hole; it is placed in a tree, a thorny bush, or a tuft of herbage. The three to six oval eggs are white or bluish with a readily-stained chalky coating; the young are soon able to skulk among the foliage. C. toulou is held sacred in Madagascar.
Sub-fam. 3. Phoenicophainae.–Taccocua sirkee, the Indian Sirkeer, has somewhat similar habits, but makes a flat nest. It is olive-brown above, relieved by black and white, and rufous below. Coua is peculiar to Madagascar, C. caerulea having loose blue plumage, glossed with violet on the tail, and dark blue naked orbits; but the other species are more olive or grey, with black or rufous on the head, throat, or mantle. The large, shy members of this handsome genus frequent the edges of forests; but whereas five species fly heavily and climb well, jumping from branch to branch with elevated rectrices, occasionally assisted by their beaks, the remaining seven rarely leave the ground, where they run about with the tail trailing. The note is a harsh "tashu" or a sharp "turruh"; the food consists of seeds, insects, worms, small mammals, birds, and molluscs–the last broken on stones; the nest of twigs and fibres is placed in high trees, and contains two or three white eggs.[[217]]
Saurothera, Hyetornis, and Piaya are the "Rain-birds" of the Bahamas and Antilles, the latter genus extending to Bolivia and Argentina. They are inactive, wary birds, which hide and creep about with outspread tails when in the trees, but are more at ease upon the ground; the cry is a loud harsh scream or cackle; the food consists of insects, berries, lizards, and mice; the flat nest contains two or three white eggs. P. cayana is reddish-brown above with a violet tinge, and grey below with pinkish throat; the tail shewing a subterminal black bar and a white tip, and the bare orbits being red. Phoenicophaës pyrrhocephalus of Ceylon is dark green, with bluish wings, blackish head and chest, tail varied with white, and white breast; the forehead and sides of the head being red and rugose. It is a fruit-eating forest species, said to be parasitic, though the allied Rhopodytes of the Indian Region lays two or three white eggs in a slight nest of sticks and leaves, while the pugnacious Rhamphococcyx calorhynchus, the "foreteller by day" of Celebes, builds a similar structure.[[218]]