This article was originally published in the Journal of the Wildlife Sound Recording Society Vol4 No4 Autumn 1982
There can be few British wildlife sound recordists who have not achieved a reasonable recording of the cuckoo Cuculus canorus and there can be even fewer who have not utilised cuckoo vocalisation as a back- ground for other spring or early summer bird song. For an atmosphere recording, the voice of the cuckoo not only indicates the phase of the calendar but, in association with other bird sound, suggests the habitat although it must be remembered that cuckoos range from reed-beds, woodland, parks or farm hedgerows to open moorland.
It is now generally accepted that a female cuckoo normally lays her eggs in the nest of the bird species in which she herself was reared; presumably, both males and females return to habitats similar to those experienced when immature. Thus, a cuckoo raised in the nest of a reed warbler Acrocephalus scirpaceus will eventually return to a lakeside or fen environment and a bird nourished in a dunnock's Prunella modularis nest will go back to countryside scattered with bushes of hawthorn or furze.
Now it is obvious that the basic "cuck-oo" phrase of the male cuckoo may vary in many respects between individual birds; commonly, there may . be differing inflections of either syllable of the call, when compared with those given by birds from adjoining territories. Differences in timing and pitch of the call also occur between individual cuckoos and, especially when early in the season, so the proportion and sequence of the "cuck"s and "oo"s may vary, so that one song type may characterise a particular bird. Male cuckoos evidently dislike to hear song from intrusive males near or in their territories; a bird will quickly fly to assert its presence under such circumstances and will approach the amplifier on replay of the song, whether it is a recording of its own voice or that of a rival.
It follows that the amateur wildlife sound recordist may be able to provide valuable information regarding the songs of cuckoos in different habitats. I wonder, for example, if there is any significant difference between the song forms and quality of the calls between cuckoos attached to different host species: it would be intriguing to have an answer to this question. No doubt it is theoretically possible that "dunnock" cuckoos are evolving recognisably distinct songs from those of "reed warbler" or "meadow pipit" Anthus pratensis birds; analysis of a sufficient number of such songs could be of great help in this problem.
It is unlikely that any serious naturalist could mistake the song and calls of the European cuckoo for those of any other common bird. Even so., every year there is confusion with the sounds uttered by the collared dove Streptopelia decaocto which has a repeated three-syllable call or song; in addition, it has an alighting call, "wah", which, with variants, is also uttered under conditions of threat. It must be admitted that a somewhat similar repeated "wah" cry is made by the cuckoo, usually in a situation or rivalry or aggression.
When a cuckoo is seen in flight, however, it is not uncommon for an inexperienced naturalist to mistake it at first for a bird-of-prey. Cuckoos, with their barred underparts, may mimic sparrowhawks Accipiter nisus although the latter have broader wings. Again, the unusual brown plumage variation of the female cuckoo suggests a similarity to that of a kestrel Falco tinnunculus. The cuckoo's flight is rapid and powerful, with wings being depressed well below the body in the downstroke and barely raised above the horizontal in the upstroke; flight is gliding or soaring on occasions, thus suggesting both the appearance and behaviour of a sparrowhawk (Ash 1965; Radford 1965). I think it is important for the sound recordist to be aware of these guises, otherwise the reactions of other birds to the cuckoo can be confused,.
At times, the reactions of small birds to cuckoos can be most dramatic, as was demonstrated by Smith and Hosking (1955). In particular, these authors showed that willow warblers Phylloscopus trochilus, when they had young in the nest, would attack a stuffed cuckoo placed close to the nest site. Physical attack was at the cuckoo's head and repeated high frequency notes were made; this call was easily recognised and distinct from the anxiety call, "hu-eet", Further experimentation showed that willow warblers under similar circumstances, would fly at and buffet a mounted cuckoo's head alone; the use of two-dimensional or non-feathered cuckoo models evoked no significant response, If a stuffed sparrowhawk, rather than a cuckoo, was displayed by the nest, then the willow warbler showed fear, using anxiety notes only and refraining from attacking the raptor,
There is no doubt that breeding willow warblers exhibit aggression towards cuckoos found in their territories and, should one be discovered, mobbing is started and the characteristic squeal-type calls given. I have also heard the same call uttered as a response to a perched kestrel, but the anxiety note "hu-eet" is made in the presence of the more dangerous sparrow- hawk, Both kestrel and sparrowhawk have a hooked beak and that of the cuckoo is slightly decurved; in all probability it is the colour and shape of the cuckoo's feathered head which small birds recognise, subsequently reacting with aggressive behaviour.
Extending their experiments, Smith and Hosking demonstrated that several other small bird species would react adversely to a mounted cuckoo when positioned near a nest with young, Nightingales Luscinia megarhynchos, for instance, made a violent attack on a stuffed cuckoo which had been introduced by a nest containing young, giving harsh, rasping calls, Moreover, nightingales were shown to behave similarly towards a mounted sparrowhawk; this activity contrasts with that of the willow warbler which has a rather complex antagonism for the cuckoo and fear for the sparrowhawk.
Of course, cuckoos are commonly attacked by small birds in the wild. I have noticed blue-grey feathers in gorse with a dunnock's nest nearby; in the nest there was a cuckoo's egg. On a moor, I once watched the commotion when a hen cuckoo glided from a bush towards a meadow pipit's nest in a heather clump; indeed, it is difficult to observe any cuckoo for any length of time without seeing, and hearing, a protesting group of birds, Curiously, Smith and Hosking noted little reaction to a stuffed cuckoo by a nesting dunnock; nevertheless, I have seen dunnocks which were very agitated in the presence of a perched cuckoo, The vocal responses of small passerines to the intrusion of a cuckoo into their breeding territories must surely make an interesting subject for investigation by recordists. Unfortunately, it is not often that the opportunity for such recordings arise in the field but, when anxiety or aggressive calls are heard from a small bird in spring or summer, it is worthwhile finding out if there is a cuckoo about. Some cuckoos are very skulking for much of the day; our attention is drawn to cuckoos when they are calling, but we should remember that the birds have to be somewhere when they are not calling.
I think it is a puzzle why some birds react so aggressively towards cuckoos. As an example, on more than one occasion I have watched a hen chaffinch Fringilla coelebs fly at the head of a cuckoo which had ventured near its nesting area; furthermore, hard, rasping calls were made which were quite unlike any chaffinch notes I had heard previously. I have a recording of these calls to prove the point (at least to me!); so far, naturalists to whom I have played the sequence have been very surprised at the identification. Yet chaffinches can only rarely be hosts for the cuckoo, certainly in Britain.
Then great tits Parus major and blue tits P. caeruleus, both hole nesters, will alarm fiercely at a cuckoo, especially when they are feeding young. So, at least blue and great tits and chaffinches will readily react against cuckoos and yet none of these species are normal British cuckoo fosterers; also, it must be very rare for the willow warbler, which is a strong anti-cuckoo reactor, as we have seen, to be parasitised by a cuckoo in this country. On the other hand, when I have watched cuckoos flying over or alighting at reed-beds where reed warblers are known to be breeding, this common fosterer has shown little aggressive activity. The male reed warbler usually gives a burst of vigorous song but little else is seen to happen. Maybe it is the vigour of the aggressive reaction which determines which bird species are selected by cuckoos as hosts.
Turning now to the young cuckoo, its vocalisations at first are a thin peeping; at about two weeks after hatching a loud wheezy type of cheeping is developed and which can be heard at several metres distance. This call attracts food-carrying birds from all around, not only its own foster parents. When the young cuckoo becomes independent, it gets mobbed by small birds, as do its true parents. Not infrequently, I have watched blackbirds Turdus merula alarming at a juvenile cuckoo, just as they will protest at a lurking adult.
But, here again, blackbirds do not normally foster cuckoos. It cannot be suggested that the calls of a young cuckoo resemble those of its fosterers either, although this does occur with certain other cuckoo species. In this connection, Mundy (1973) has pointed out that in Europe the vocalisations of nestling great spotted cuckoos Clamator glandarius are like those of fledgling magpies Pica pica; this means, in effect, that acoustic mimicry for the host's young has been evolved at least by this cuckoo species. Incidentally, a mechanical sound I have heard produced by a young cuckoo, although it could just as readily have been made by an adult, is the beating of a long, hairy caterpillar on a rock. Probably, being newly independent, a juvenile cuckoo would take longer over the process than an experienced bird. A hairy caterpillar, when secured, is softened by nibbling with the bill before being swallowed but, presumably for a tough Specimen, it may be beaten, almost as a song thrush Turdus philomelos hammers a snail on its anvil. On moorland, such caterpillars are often oak eggars Lasiocampa quercus.
The various vocalisations of the cuckoo have been considered in detail both by Chance (1940) and by Wyllie (1981). After reading these accounts, it appears that there is no good evidence that the "cuck-oo" call is ever made by the female. The typical sound produced by the female, of course, is the "bubbling" call. This is associated with egg-laying; hence it is often heard in the late afternoon or evening when the bird usually lays - contrasting with most other birds which lay in the morning. If "bubbling" cries are heard, especially if a female cuckoo has been seen to glide down from a vantage point, it is likely that an egg has been laid. Interestingly Wyllie has described how he heard a male cuckoo "bubble" at the end of its normal song.
An uncommon cuckoo call, also mentioned by Wyllie, is a snake-like hiss It is thought that this sound may be made as a gesture to frighten off mobbing birds or during courtship activities. Certainly I have not heard a cuckoo hiss myself but I once heard a mewing sound emitted by a female: this call was described by Chance. The much commoner "wah" call, which may be confused with cries of the collared dove, has already been discussed, Clearly, there is much scope for the wildlife sound recordist in attempting to tape the varied vocabulary of the cuckoo,.
Unfortunately, the duration of the season in which one may hear cuckoo sounds is all too brief; in addition, we all know the frustration sensed when unusual sounds are ruined by a roaring motor-cycle or low aircraft. However, there is doubtless as much to be learned in the analysis of cuckoo calls and song as there is in consideration of the sounds made by birds reacting to the presence of a cuckoo. The amateur sound recordist is surely well placed to make a contribution to this fascinating subject.
Now a "geck" is one old dialect name for the cuckoo; geck means a dupe but it seems to me that it is the parasitised birds which are duped, certainly not the cuckoo. Another country cuckoo name is "gawk" which implies the bird is ungainly. While the cuckoo may seem to be awkward when attempting to walk on its short legs, it is certainly not so in its rapid, sure flight, Nor is the cuckoo a gawk as it sings from a dewy branch as a Way dawn breaks: as it calls, so the tail rises and the thin, pointed wings are depressed in a smooth rhythm, The bird is neither a gawk nor a geck; without doubt it has a poise and mystery unique to itself, I have to confess that when, on the several occasions when I have tried in vain to record a calling cuckoo, I have felt that I have been the geck and not the enigmatic bird which has lured me.
ASH, J.S.1965. The 'raptor-flight' of the Cuckoo. Brit. Birds
CHANCE, E.1940. The Truth about the Cuckoo, Country Life, London.
MUNDY, P.J. 1973. Vocal mimicry of their hosts by nestlings of the Great Spotted Cuckoo and Striped Crested Cuckoo, Ibis 115: 602-604.
RADFORD, A,P. 1965. The 'raptor-flight' of the Cuckoo. Brit.Birds 58: 155.
SMITH, S. and BOSKING, E. 1955. Birds Fighting, Faber and Faber. London.
WYLLIE, I. 1981. The Cuckoo, Batsford. London,