CUCKOO 



are blackish, and mottled with yellow and gray. 

 A reddish variety occasionally occurs. The bird 

 M in Nnrtli Kiirn|iu in April or May, and 

 leaver again in Anguat or September. Its cheerful 

 call ceases to IK) heard about the middle of June. 

 Predominantly an arl>oreal bird, it is rare in tree- 

 leas districts. Each cuckoo .scons jealously to 

 preserve"' a certain territory for itscli. Like the 

 other s; ics of Cuculus, it is a shy, restless, un- 

 social bird. It is extremely valuable on account 

 of its insatiable appetite for caterpillars. The 

 hairy forms an; especially delighted in, and the 

 indigestible hairs form a felt-like coating in the 

 Moniach. The female lays its eggs singly (some- 

 times to the nn in I MM- of eight), eacli in the nest of 

 some suitable bird, choosing such as feed their own 

 young on insects in order of preference, hedge- 

 sparrow, water- wagtail, titlark, yellow-hammer, 

 green linnet, and whin-chat. The young cuckoo, 

 unconsciously reared by its foster-parents, manages 

 to secure the bulk of the food-supply, and in the 

 struggle for existence completely monopolises the 

 nest, ousting the rightful brood. Stories of the 

 ungrateful young bird devouring its foster-parent 

 are entirely mythical. Nor has it been shown that 

 the adult ever sucks the eggs of other birds. The 

 males greatly outnumber the females. The latter 

 have somewhat darker feathers, and a somewhat 

 less emphatic note. The males are said to be very 

 passionate in their love-making, but there is no 

 regular pairing or continued attachment. The 

 musical interval between the cuckoo's two notes is 

 not uniform, and varies from a minor to a major 

 third (the latter being^ that adopted in Beethoven's 

 reproduction ). See Nature, vol. xxxvi. p. 344. 



The genus Cuculus includes about a score of 

 other species, restricted to the eastern hemisphere. 

 In the same family as the true cuckoos are several 

 i m nortant genera : The Honey-guide (Indicator), of 

 Ethiopian distribution, feeding chiefly on wild bees, 

 and directing attention to their nests ; the Golden 

 Cuckoo ( Chrysococcyx ) ; the Jay-cuckoo (Coc- 

 cystes), utilising the nests of crows and magpies ; 

 Eudynamis, of similar habit ; Scythrops, a very large 

 form in Australia, New Guinea, and the Celebes ; 

 the swift ' Road-runner ' or ' Ground Cuckoo ' 

 (Geococcyx), of California; the grub-eating Ani- 

 binl (Crotophaga, q.v. ); the Coucal or Spurred 

 Cuckoo ( Centropus ), with the claw of the inner toe 

 prolonged into a great spur. An East African 

 cuckoo (Tepe-tepe) is a delightful song-bird. The 

 American Cuckoo (Coccyztis americanits) is par- 

 ticularly interesting, since it makes but a very 

 rudimentary nest, has a very irregular way of lay- 

 ing, and exhibits an unnatural indifference to its 

 young. Its egg is occasionally found in the nest 

 of other birds. These facts, according to Bur- 

 roughs, raise the question whether the American 

 cuckoo ' is slowly relapsing into the habit of the 

 European species, which always foists its egg upon 

 other birds ; or whether, on the other hand, it be 

 not mending its manners in this respect. ' 



The parasitic habit of our common cuckoo 

 demands further attention, as one of the strangest 

 of bird habits. The facts, which are very hard to 

 explain, may be thus summarised : ( 1 ) The habit 

 of utilising the nests and bnxxling patience of 

 other birds is not common to the genus. It is also 

 the practice of an Australian species, and of some 

 related genera, and is occasionally exhibited by the 

 American representative. Professor Newton notes 

 that a few or our common birds, ' whether by mis- 

 take or stupidity, not unfrequently lay their eggs 

 in the nests of others.' In the genus Molothrus, 

 allied to starlings, and far separated from cuckoos, 

 the various species exhibit a gradual perfecting ( if 

 we may use the term in such a connection) of the 

 parasitic habit. (2) The modus operandi of the 



habit is usually as follows : The cuckoo aelecth tlm 

 nest of an insect-eating bird, much smaller than 

 herself, and often with eggs approximately like her 

 own. Into this, nay of a hedge sparrow, she liiu 

 her egg with her bill, having previously laid it upon 

 the ground. After an interval of two or three 

 days, she repeats the process in another nest. The 

 hedge-sparrow or other bird, all unaware apparently 

 of what has happened, site on the cuckoo-egg along 

 with her own. The young cuckoo is generally 

 hatched first, and is restless and uneasy until it has 



Sot rid of the other eggs or young birds. This it 

 oes with considerable exertion, and sometimes 

 with a real struggle, by lifting the living burden 

 upon its back and throwing it over the side of the 

 nest. Thereafter it remains sole though wrongful 

 possessor, and is reared in peace. (3) Among the 

 tacts which make the habit a success, the following 

 should be noted. The relatively small size of the 

 cuckoo's egg is striking. ' The egg of the cuckoo 

 is not any larger than that of the skylark, although 

 an adult cuckoo is four times the .-!/ of an adult 

 skylark.' This makes the duping of the small 

 birds easier, if, indeed, they have any suspicions. 

 The laying of the egg in a small bird's nest makes 

 the ousting work of the young cuckoo an easier 

 task. In many cases, as already noted, the cuckoo's 

 egg is coloured approximately like those of the 

 victimised foster-parent. Till the young cuckoo is 

 about twelve days old, when the disposition for 

 turning out its companions begins, according to 

 Jenner, to decline, its broad back has a curious 

 depression in the middle. The presence of this 

 cavity makes it easier for the restless and still 

 sightless nestling to bear up and toss over the eggs 

 or young birds which interfere with its desire for 

 sole possession. (4) The advantage to the young 

 bird, which earns by its exertions plentv of growing- 

 room and an extra portion of food, is obvious 

 enough. The individual parent is also saved both 

 time and trouble, as well as all the patient sacrifice 

 of brooding. Jenner has pointed out that the 

 advantage to the species is probably this, that by 

 leaving their eggs to other oirds to incubate, the 

 cuckoos are able to have a numerous progeny 

 reared in the short period of their stay in northern 

 Europe. Or, to put it in another way, the para- 

 sitic nabit enables the cuckoos to migrate earlier. 

 Hence Darwin believed the constant parasitic 

 habit of our cuckoo to have been derived from 

 its occasional occurrence (as in the American 

 form) through the action of natural selection. 

 Those cuckoos which fell in with the trick suc- 

 ceeded better than their neighbours, till gradually 

 only those survived in whom the trick had become 

 habitual. 



It is interesting in this connection to note the 

 occasional reversion of a cuckoo to parental re- 

 sponsibilities. Mr Romanes has given a detailed 

 discussion of the subject in his work on Animal 

 Intelligence, and also comes to the conclusion that 

 ' we are justified in setting down the instinct to the 

 creating influence of natural selection.' It ought 

 not, however, to be overlooked that all the cuckoos 

 are solitary, unsocial birds; that the American 

 genus is said to be immorally uninterested in the 

 fate of the young; that the species of Molothrus, 

 which has most completely developed the parasitic 

 habit, is extremely careless about the brood, and 

 often drops its eggs on the bare ground. The habit 

 may be regarded not so much as requiring special 

 explanation, as an expression of a general constitu- 

 tion or habit of life. Brehm describes the cuckoo 

 as a greedy, discontented, ill-conditioned, passion- 

 ate, in short, decidedly unamiable bird. It seems 

 plausible, therefore, to suggest that one dominant 

 ' physiological tendency ' or mood shows itself in 

 the restless selfishness of the nestling, in the 



