AUSTRALIAN 236 BIRD WATCHER
AUSTRALIAN BIRD WATCHER 1996, 16, 236-249
The Juvenile Food-begging Calls, Food-swallowing Vocalisation and Begging Postures in Australian Cockatoos
by JOHN COURTNEY, 'Ashgrove', Swan Vale, via Glen Innes, N.S.W. 2370
Summary The juvenile food-begging calls, food-swallowing vocalisation and begging postures of cockatoos were studied and compared with those of other Australian parrots. The begging call of most cockatoos is a repetitive harsh-sounding wheeze, differing in tone from the hissing begging note of lorikeets, and quite different in tone, structure and tempo from the whistling begging notes of most other Australian parrots (descriptions of which will be presented in three subsequent papers). The food-swallowing vocalisation seems to be unique to the cockatoos. Only two species of cockatoo, thought to be the most 'primitive' (Cockatiel Nymphicus hollandicus and Gang-gang Callocephalonfimbriatum), have the same begging posture as most other parrots. The occurrence of a basically similar 'straight' wheezing begging note, and possession of a food-swallowing vocalisation, in all five genera of the cockatoos reflect a degree of uniformity in this natural group that is surprising in view of its apparently ancient lineage. Introduction A vocalisation generally known as the juvenile food-begging call is present in .the chicks of most species of birds having altricial young. The wide inter-order occurrence of this vocalisation throughout the world indicates that it is a fundamental biological feature, the function of which is to initiate and regulate the feeding of chicks by the parents. Hiichtkerl & Schwartzkopf (1958) demonstrated that surgically deafened caged Bullfinches Pyrrhula pyrrhula functioned as well as birds with normal hearing, except that, being unable to hear the begging calls of their nestlings, these were fed so poorly that they soon died of starvation. Thus, the begging call would seem to be the first vocalisation uttered in the ontogeny of an individual altricial bird that is vital to its survival. [See Welty (1964, p. 191 and pp. 328-329) for a summary in English of this observation and others of relevance to the subject, especially the ingenious experiments of von Haartman (1953).] Juvenile food-begging calls invariably consist of a single, simple repeated note, thus differing from the elaborate and complex sounds of most birds in other vocal communication and territorial advertisement. The begging call is species-specific, in that all young of a given species sound alike (to human ears), within a range of sound peculiar to that species. However, this vocalisation varies so much in pitch, tone, timing and general construction between the different natural groups of birds that random duplication in this sound between unrelated species would seem to be rare or unlikely, except where similarities are guided by natural selection or other means as in cuckoo chicks mimicking the calls of chicks of host species (Courtney 1967, Mundy 1973, Mundy & Cook 1977). Though the begging call is species-specific, and differs greatly among unrelated species and genera, there is an undeniable similarity in this call between closely related species and genera among Australian species examined, not only in the Psittaciformes but in the Strigiformes and Passeriformes as well (pers. obs.). This suggests that the begging call is slow to change, apparently because it is unlikely to be influenced by the external evolutionary pressures that more quickly shape morphological characters. If there is n6 direct need for change, it may come only slowly by evolutionary drift. The fixed nature of the begging call therefore seems to qualify this vocalisation as a valid taxonomic character. The general principle that the 'juvenile food-begging call is closely similar in closely related species, and bears little or no resemblance in distantly or unrelated species respectively, thus VOL. 16 (6) JUNE 1996 Juvenile Cockatoo Vocalisations 237 indicating relationships' (Courtney 1986a) was first put forward in a tape-recorded lecture at a symposium on parrots, convened by the Royal Australasian Ornithologists Union, on 11 May 1978 at Melbourne University, reported by Anon. [ =MM] (1978). Since then, this principle has been applied to some cockatoos (Courtney 1986a,b, 1993). The juvenile food-begging calls in the lecture (above) have now been incorporated into the Field Guide to Australian Bird Song cassette series, and for audio examples of the vocalisations in this paper refer to Buckingham & Jackson ( 1988, 1990). Virtually all of the sonagrams in the present paper are from the above tapes. ·A copy of the RAOU lecture tape has been lodged with the Australian National Wildlife Collection, CSIRO, Canberra. The present study involving the sound-recording of the juvenile food-begging calls of all possible species of Australian parrots was begun in 1963, though the initial work, before sound-recording equipment was readily available, began eleven years earlier (Courtney 1974). The aim of this ongoing project is twofold: to add this information to the life-history of each species for its intrinsic value; and to compare the begging calls of each species in order to draw taxonomic conclusions, which may help clarify the phylogeny of the Australian Psittaciformes (Courtney 1986a). The begging calls and other juvenile factors in the Australian parrots differ widely between the different natural groups and are largely group-specific. In contrast with most of these groups, young cockatoos utter a slow, repetitive wheezing note, modified in tone in the black-cockatoos Calyptorhynchus to a rasp or a squeak. Cockatoos seem unique among the Psittaciformes in possessing a juvenile food-swallowing vocalisation (Courtney 1974). The purpose of this paper is to place on record a description of the juvenile food-begging calls, food-swallowing vocalisation, begging postures and associated behaviour in the Australian cockatoos as a foundation for future, more comprehensive work in this field. The juvenile begging calls of the three other Australian parrot groups (the broad-tailed or platycercine parrots, the 'rose-tailed' or polytelitine parrots and the lorikeets) will be described in subsequent papers.
Methods Nestlings were mostly obtained on loan from avicultural sources, except for a few parrots and some cockatoos, and reared by hand. This enabled high-quality tape-recordings to be made under isolated auditory conditions free of extraneous noise, and also gave the opportunity to observe closely other associated behaviour such as food-begging posture. Sound-recording equipment included Uher 4000 Report Land Akai X-IV open-reel portable tape-recorders; Sony TC 158 SD, TC D5PRO, WM D6C Professional and Marantz CP 430 cassette tape-recorders; with Uher M516, Uher M538, Akai X-IV issue, Sennheiser MD 21-2 and Nakamichi CM 300 microphones. Recordings obtained in the field, as controls or when young failed to perform, were made with one of the above microphones mounted in a 61 em (24 in.) Grampian parabolic reflector or the Nakamichi CM 300 microphone with CP-4 shotgun capsule, tripod-supported. Sonagrams were produced from some calls, for visual presentation and analysis. Other equipment used was mentioned in Courtney (1986a). Although open-reel ' recorders gave the best results, cassette recorders were more convenient when a number of young had to be reared (in isolation) over the same period, for cassette tapes can be interchanged rapidly on the recorder, enabling separate tapes to be maintained for individual young or groups of siblings. Sonagrams were produced on a Kay Spectrum Analyser 7030A mostly using the wide-band filter (300 Hz); exceptions (narrow-band filter, 45 Hz) are noted in figure captions. Unlike complex bird-song, which requires elaborate equipment to record itSuccessfully, juvenile food-begging calls are basically simple sounds easily handled by modem cassette-recording equipment. Thus, there is enormous scope for the many people throughout the world who annually hand-rear young parrots and other birds, especially those of rare and vanishing species, to make a significant contribution to knowledge by simply recording their calls on domestic recording equipment used in most homes. These recordings can then be preserved for posterity, such as at the Australian National Wildlife Collection (CSIRO Division of Wildlife & Ecology, P.O. Box 84, Lyneham, A.C.T. 2602); the Library of Natural Sounds, Laboratory of Ornithology, Cornell University, New York, U.S.A.; or at the National Sound Archive, Wildlife Section, The British Library, 29 Exhibition Road, London SW7 2AS, U.K. AUSTRALIAN 238 COURTNEY BIRD WATCHER
Results
Food-begging posture In addition to the auditory stimulation to parents of the begging call, chicks usually reinforce this with visual signals as well in the form of begging postures used in conjunction with the begging call. Young of the Cockatiel Nymphicus hollandicus and Gang-gang Cockatoo Callocephalon fimbriatum bob their heads up and down in an irregular fashion: on outstretched necks, when soliciting food. The young of Calyptorhynchus simply sit in a slightly crouched fashion, and seem to concentrate all of their begging activity into their loud and monotonous begging call which goes on for hours, if need be, until the young are sated. Unfortunately, for a complete picture of the begging postures of cockatoos, there seems to be no record of this stance in the Palm Cockatoo Probosciger aterrimus, but G.A. Smith (in litt. 1984) stated that his young bird did not head-bob when begging. The young of Cacatua have departed dramatically from the rest of the cockatoos in begging posture, and have adopted a slow, rhythmic swaying in conjunction with the food-begging call. In the Galah Cacatua roseicapilla, corella complex and the Sulphur-crested Cockatoo C. galerita, the young slowly sway the head and body from side to side in a wide arc while uttering the begging call. Major Mitchell's Cockatoo C. leadbeateri alone acts in an atypical way in 'swaying', by slowly and rhythmically rocking the head and body forwards and back in a deep bowing motion (Courtney 1993), at least in the nine young of three geographically separated eastern Australian broods observed by me.
Breath-drawing 'pip' vocalisation All members of Cacatua utter, to a greater or lesser degree according to species, a brief pip vocalisation, most prominent in the Galah and corella complex, that is sandwiched between each note of the begging call. It is very brief in duration, about 180-250 ms, and compared with the wheezy begging call is purer in tone with more distinct attendant harmonics. This idiosyncrasy in association with begging calls is unique to the Cacatua genus, except that a hint of this sound seems to occur at times also in Probosciger (Courtney 1993). It has not been recorded in Nymphicus, Callocephalon or Calyptorhynchus. It is usually absent in downy young Cacatua, but a six-day-old Western Corella C. pastinator was heard to use it (pers. obs.). In large feathered nestlings and fledglings, it is almost always present in all individuals of the Galah and corella complex, is present in only some individuals of the Sulphur crested Cockatoo (but when present is consistently uttered in those individuals), and though present in all individual young Major Mitchell's Cockatoos, is only made by them some of the time. The function of this curious vocalisation is not known, but seems to be caused by the bird making a quick gasp for air in between begging notes. Why it should be uttered by some species (Cacatua) and not by others (non-Cacatua), and by some individuals and not others (within Cacatua), is not clear, when all have much the same spacing between begging notes. This note was briefly mentioned, but not assigned any name, by Pidgeon (1981) in his study of the vocalisations of the Galah, and was referred to as the 'Breath-drawing "Pip" Vocalisation' by Courtney (1993).
Feeding-pause vocalisation A strongly quavering note has been recorded under this terminology (Courtney 1974), which seems to be simply a functionless idiosyncrasy of the Cacatua and Nymphicus genera, used in the transition stage between food-swallowing and the full VOL. 16 (6) JUNE 1996 Juvenile Cockatoo Vocalisations 239
8
7 food-begging ca_!l food-swallowing vocalisation 6
Hz 4
3
0
COCKATIEL 1 sec. 2sec.
Figure 1. Juvenile food-begging call and food-swallowing vocalisation of the Cockatiel (wide-band filter, 300 Hz).
food-begging modified to whistling tone food-begging
i • s{~:;"tt{~?; / ~{.~';·~ ' .~ . . . -. :.....~ ~}J. l. _ ~ . . -~,.-- . ; .~ ,:.. · ·,~· : l -:.~- \J~ ·: . ~. ~\.l"J ! r
: ...... ~ --....-~ .· ..... ~,) ..~ .. · "' ~· ~ .1 _Q I COCKATIEL 1 ~ec. 2 i ec.
Figure 2. Juvenile Cockatiel: normal begging wheeze modified to whistling tone (narrow band filter, 45 Hz).
food-begging call food-swallowing vocalisation
4
Figure 3. Juvenile food-begging call and food-swallowing vocalisation of the Gang-gang Cockatoo (gap of 3-4 sec. between begging and swallowing vocalisations edited out). resumption of the begging call. It is noteworthy, however, as characteristic of these genera. Food-swallowing vocalisation Cockatoos appear to be unique among the parrots of the world in possessing a food swallowing vocalisation, which is quite different from, and ought not be confused with, the food-begging call. Courtney (1974) simply referred to it as the 'Food swallowing Vocalisation', because it is used by all species of cockatoo except the Glossy Black-Cockatoo Calyptorhynchus lathami, and probably the Red-tailed Black-Cockatoo AUSTRALIAN 240 COURTNEY BIRD WATCHER
C. banksii. Since then, in a study ofthe Galah, Pidgeon (1981) used the term 'F-call' when referring to the food-swallowing vocalisation in that species and, similarly, Saunders (1983) used the term 'feeding A ... A ... A ... call' in a study of the Short billed Black-Cockatoo Calyptorhynchus latirostris. Courtney (1983) suggested that the term 'Food-swallowing Vocalisation' was adequate for all species for the sake of uniformity and that, if abbreviation were needed, the term [cockatoo] 'FSV-sound' ought to be adequate. The cockatoo food-swallowing vocalisation is a series of short, rapidly repeated notes uttered by young cockatoos when they are actually engaged in swallowing food that is being transferred from the bill of a parent. During this process, the opened bills of young and parent are locked together and regurgitated food is transferred while the heads and necks are jerked violently up and down. The vocalisation appears to be synchronised with, and linked to, the violent head-jerking, because the two species of cockatoo (Glossy and Red-tailed Black-Cockatoos) that do not utter this sound do not make violent jerking movements of the head. Instead, they bob their heads up and down in a very restrained fashion, as do the young and parents of other parrots which also do not utter this sound (Courtney 1974). This food-swallowing vocalisation for the various species is illustrated along with the accompanying sonagrams of the food-begging calls, for both occur close together.
Food-begging calls It is stressed that in the following descriptions of begging calls, all measurements of time and repetition rates must be regarded as approximate. Although sonagrams were carefully measured and long series of tape-recorded calls were counted and timed by stopwatch, it was found that considerable differences do occur in, and between, individuals. Low-intensity begging when the young are not hungry, combined with high-intensity begging when the young are very hungry (with all stages in between), almost certainly account for this variation. However, the extremes would still fall within a range peculiar to that species. The Cockatiel has a simple, brief, repetitive hissing-wheezy begging call. In the tapes examined, the begging note varies from about 800 ms (i.e. eight-tenths of 1 second) to 1 second in duration, and consists of a wide band of scattered frequencies from 0.5 to 5 kHz, with energy concentrations at 1.25, 1.75 and 4kHz. It has a repetition rate of about 50 to 70 notes per minute (mean rate 60 per min.), and has a gap of about 80 to 130 ms between each note (Figure 1). Sometimes the wheezing note briefly lapses into a clear whistling tone (Figure 2), like Cacatua. The Gang-gang Cockatoo also has a very simple begging call. The poor-quality tape-recording obtained here (Figure 3) suggests that the begging note is about 600-900 ms long, and consists of a wide band of stronger scattered frequencies up to 3kHz, with weak scattered frequencies above that to about 6kHz, the effect being a simple, straight brief wheezing note, with a tonal quality resembling other calls of this species, and lacking the harsh quality of Cacatua. There are gaps of 50 to 100 ms between notes, suggesting a possible begging rate of about 60 notes per minute (a 900 ms note + 100 ms gap). There appear to be energy concentrations at about 0.25 kHz and again at 2.5 kHz (Figure 3). Immediately before and often during food begging, the young vary the straight, even, wheezing note by uttering preliminary begging notes of erratic length and timing which, combined with the unique tone of the Gang-gang, sound reminiscent of buzzing Morse code. Unlike the previous two monotypic genera, the single individual of the Palm Cockatoo recorded had a rather lengthy begging note with minimal gap (about 80 ms) between calls (Figure 4, showing 'gap' but not frequency bands) and, with its wheezing VOL. 16 (6) JUNE 1996 Juvenile Cockatoo Vocalisations 241
5 4
Figure 4. Juvenile food-begging call of the Palm Cockatoo, showing gap between calls.
5
Figure 5. Juvenile food-begging call of the Palm Cockatoo, showing frequency bands.
8 breath-drawing food-begging call food-begging call food-swallowing vocalisation 7 'pip' noise I I
Figure 6. Juvenile food-begging call, breath-drawing 'pip' and food-swallowing vocalisation of the Galah.
quality, sounded reminiscent of a young Sulphur-crested Cockatoo. Each note was about 2.5 seconds long and, unlike the Sulphur-crested Cockatoo, consisted of about nine narrow bands of frequencies of similar inten-sity up to about 4.5 kHz (Figure 5). The repetition rate was about 23-24 notes per minute. This individual was the first ofthe species successfully bred in Britain (Smith 1985, Low 1986), and the tape recording was kindly made available by its owner, G.A. Smith. It is important to note that this single example may not be completely typical of the species in the wild. The Galah has a wheezing begging note about 700-770 ms long with a 'gap' of about 230 ms which, however, contains the breath-drawing pip noise. When timed by stopwatch, a long series of calls averaged one per second ( = 60 notes per minute, including the breath-drawing pip noise between). Though there are faint traces of scattered frequencies up to at least 11 kHz on sonagrams, most energy ceases at between 7 and 8kHz, with distinct bands of energy beginning at 1, 2, 3 and 4kHz respectively (Figure 6). Pidgeon (1981) reconted the call as having little structure AUSTRALIAN 242 COURTNEY BIRD WATCHER
6 . Qreath- 4 kHz 3 ' '1 2 ~··~ ~ i 0 MAJOR MITCHELL'S COCKATOO 1 sec. 2sec. Figure 7. Juvenile food-begging call and breath-drawing 'pip' of Major Mitchell's Cockatoo (narrow-band filter, 45Hz). 8 breath-drawing 7 food-begging call food-swallowing vocalisation 'pip' noise 6 5 Figure 8. Juvenile food-begging call and food-swallowing vocalisation of Major Mitchell's Cockatoo (wide-band filter). and most energy between 0.5 and 2.0 kHz. The other members of Cacatua studied all had much longer begging notes than the Galah, although in Major Mitchell's Cockatoo this was marginal at times. Though sometimes the begging note in Major Mitchell's Cockatoo can be quite long, usually they are around 1.05 to 1.35 seconds, plus 0.2 to 0.25 seconds (200-250 ms) for the breath-drawing pip noise (Figure 7) . The fastest calling rate averages about 45 begging calls per minute, but is usually much less. The tone is very harsh, nasal and wheezing, with scattered frequencies from 0.5 to 5.5 kHz, the main energy band being from 2 to 2.5 kHz (Figure 8). The Long-billed Corella Cacatua tenuirostris has a long, wheezing begging note with scattered low-energy frequencies as high as 6 kHz. Most of the energy was centred on two bands at 1.25 and 2.5 kHz, and there was a third weaker band at 4kHz in the individual studied (Figure 9). The begging note varies much in length in the same individual from about 1.5 to greater than 3 seconds each, but most are around 2 seconds ( = 30 per minute). The breath-drawing pip noise is prominent and very quickly uttered in this species, occupying about 180 ms (Figure 10) . The begging call in other corella species has not been studied, except for a brief observation of two Little Corellas C. sanguinea (Figure 11). The Sulphur-crested Cockatoo has the longest wheezing begging note of the genus in Australia, usually about 4 seconds in duration plus 200 ms for the breath-drawing pip noise, so that the repetition rate is only about 14.2 calls per miaute. Scattered frequencies reach up to 5.5 kHz, some higher, but almost all of the energy is VOL. 16 (6) JUNE 1996 Juvenile Cockatoo Vocalisations 243 7 food-swallowing 6 food-begging call 5 vocalisation 4 kHz 3 2 0 Figure 9. Juvenile food-begging call and food-swallowing vocalisation of the Long-billed Corella. 11 10 9 8 7 kHz 6 ... ' ,- . . 4 ' ·.:- - y• ~• . _._ ~ 2 ~~~~· ii:.~. ~~~~-~~ r:~:;:~., ( ~ ~?:~~~~t~',?;~~-~~":·~-·--- \ 0 LONG-BILLED CORELLA 1 sec. 2sec. Figure 10. Juvenile Long-billed Corella: long column is breath-drawing 'pip'. concentrated in two thick bands centring on 1.5 and 3 kHz (Figure 12). At times the wheezing note briefly lapses into a clear whistling tone (Figure 13); this also occurs in the Cockatiel, and less often in other members of Cacatua. There are two superspecies in the genus Calyptorhynchus, one consisting of the white-tailed and yellow-tailed black-cockatoos of the baudinii-latirostris-xanthanotus funereus complex, and the other is formed by the two red-tailed species of the lathami banksii group (Adams et al. 1984). Young of the funereus superspecies utter a repetitive, harsh, rasping begging call and in addition also utter the cockatoo food swallowing vocalisation, whereas young of the red-tailed group utter a clear squeaking begging call and appear to be the only cockatoos that lack the food-swallowing vocalisation, thus differing markedly within a genus (Courtney 1974, 1986b). Saunders (1983), in a study of the vocal repertoire of the Short-billed Black Cockatoo, has shown that the young utter two distinct calls, which he termed the 'grate' and the 'begging grate'. The 'grate' has virtually no structure, is uttered for AUSTRALIAN 244 COURTNEY BIRD WATCHER 6 5 kHz 4 3 2 0 Figure 11. Juvenile food-begging call of the Little Corella. 8 breath-drawing food-swallowing 7 food-begging call ·'pip' noise vocalisation 6 5 Figure 12. Juvenile food-begging call, breath-drawing 'pip' and food-swallowing vocalisation of the Sulphur-crested Cockatoo. 2 (1) (2) ~ (3) ~ l ·· ~)~,~~ _. ~ \ ~ ...... Q ~~--~-r~~~r-r-~o--r-r~~~r-r-~o-~-r-,- SULPHUR-CRESTED COCKATOO 1 sec. 2sec. Figure 13. Juvenile Sulphur-crested Cockatoo: (1) begging wheeze, (2) lapse into clear whistling tone, (3) breath-drawing 'pip'. long periods, and does not seem to attract a response from parents. The 'begging grate' does have some structure in the form of distinct harmonics, and is made before being fed by the parents. He noted that this call varies from low brief grates to loud, harsh continuous grates that may go on for minutes. Obviously, the rate of calling and length of note in this species varies according to mood (degree of hunger). There seems no reason to suppose that this basic picture would be any different in any of the other members of the superspecies, except that the difference between the so called 'grate' and 'begging grate' would be harder to distinguish in the Yellow-tailed Black-Cockatoo C. f funereus, for all of its begging notes seem somewhat structureless, and rather like the 'grate' of the Short-billed Black-Cockatoo. In the VOL. 16 (6) JUNE 1996 Juvenile Cockatoo Vocalisations 245 8 7 food-begging call food-swallowing vocalisation 6 5 Hz4 2 0 YELLOW-TAILED BLACK-COCKATOO 1 sec. 2sec. Figure 14. Juvenile food-begging call and food-swallowing vocalisation of the Yellow-tailed Black-Cockatoo (northern race junereus). food-begging call food-swallowing vocalisation SHORT-BILLED BLACK-COCKATOO 1 sec. 2sec. Figure IS. Juvenile food-begging call and food-swallowing vocalisation of the Short-billed Black-Cockatoo. food-begging call food-begging call 7 6 5 l+:l Hz4 . . 3 . 2 ~ -- 0 I GLOSSY BLACK-COCKATOO 1 ~ec . 2sec. Figure 16. Juvenile food-begging call of the Glossy Black-Cockatoo. latter species, the 'grate' call may be low-intensity food-begging, which probably functions as a location call and as a stimulus to parents to gather more food than they would normally do to maintain themselves, whereas the 'begging grate' triggers a response to actually feed the young. Bearing in mind the difficulties of interpretation of low-intensity and high-intensity begging in the superspecies, the following comments on the begging calls of the northern Yellow-taih:d Black-Cockatoo and the Short billed Black-Cockatoo are given; examples of these calls in the Long-billed Black Cockatoo C. baudinii and southern Yellow-tailed Black-Cockatoo C. f xanthanotus are not available. AUSTRALIAN 246 COURTNEY BIRD WATCHER 8 adult call begging wheeze begging wheeze 7 6 5 Hz4 3 2 0 RED-TAILED BLACK-COCKATOO 1 sec. 2sec. Figure 17. Juvenile food-begging call of the Red-tailed Black-Cockatoo. 9 8 7 .\lli\1,'11', 6 .;,, ,~ ,1~\ii, 5 Hz 4 3 2 GLOSSY BLACK-COCKATOO 1 sec. 2sec. Figure 18. Juvenile food-begging call of the Glossy Black-Cockatoo: 'wheezy' example. H 7 6 0 RED-TAILED BLACK-COCKATOO Figure 19. Example of wheezy food-begging call of the juvenile Red-tailed Black-Cockatoo, similar to wheezy Glossy Black-Cockatoo (cf. Figure 18). The begging call of the northern Yellow-tailed Black-Cockatoo is a harsh, repetitive rasping sound consisting mainly of a somewhat unstructured band of noise from 0.5 to 4 kHz. The length of the note varies considerably in each individual, probably influenced by degree of hunger, and is often between 330 and 450 ms, at times longer, with a separation gap of about 120 ms during which no sound is made. The three calls depicted (Figure 14) show a repetition rate of about 133.3 notes per minute, which seems fast. Because feeding immediately followed, this was the 'begging grate' in the sense of Saunders (1983) and not the low-intensity 'grate'. Most calling recorded VOL. 16 (6) JUNE 1996 Juvenile Cockatoo Vocalisations 247 in the wild is much slower, having a repetition rate of from 65 to 73 notes per minute, but .here it is difficult to interpret intensity. The begging call of the Short- billed Black Cockatoo, though covering the same frequency range as June reus, is more pure sounding with at least six bands of harmonics, each note recorded in this study being about 520 ms duration with a 230 ms separation gap, the repetition rate depicted (Figure 15) being about 85 calls per minute. Curiously, the food-swallowing vocalisation notes of latirostris are only about half the length of June reus and are given at a faster rate (8.6 calls per second cf. 6.4; see Courtney 1986a). The begging call of the Glossy Black-Cockatoo sounds like a brief, clear, high pitched squeak, slowly repeated. On a sonagram (Figure 16) the begging note is a fairly pure call with an ascending (3.0-4.5 kHz) whistle, but some sidebands occur in the middle of the call. As shown, each call is approximately 390 ms in duration with an interval between calls of 1.2 seconds, thus giving a repetition rate of 38 calls per minute (Courtney 1986b). However, a long series of calls timed by stopwatch gave a rate of only 24-26 calls per minute, which seemed the normal rate of calling (the calls tend to speed up with increasing hunger). The Red-tailed Black-Cockatoo has not been studied closely but of the two individuals briefly observed, the begging call was a squeak closely resembling that of the Glossy Black-Cockatoo and, as in the latter, no food-swallowing vocalisation was made (Figure 17). The difference, if any, in the begging calls between these two species would seem to amount to only trivial variations in pitch and tone. Indeed, some individual Glossy Black-Cockatoos have more 'wheeze' than most (Figure 18), and are close to some juvenile food-begging calls of the Red-tailed Black-Cockatoo (Figure 19). Discussion and conclusions In summary, the present study has shown that the cockatoos appear unique in their possession of a food-swallowing vocalisation, not apparent in any other parrot. Their straight, wheezing food-begging calls that are mostly lacking in structure also set them apart from other Australian parrots which, except for the lorikeets, have structured begging calls. The breath-drawing pip noise present in all species of Australian Cacatua cockatoos, and not apparent in any other cockatoo, makes this vocalisation a definitive Cacatua characteristic. The harsh, coarse, droning wheezing tone of the begging call in the Galah and other Cacatua cockatoos sounds alike in those species, but different from the soft buzzing-wheeze of the Gang-gang Cockatoo or soft hissing-wheeze of the Cockatiel. This tonal similarity, combined with the strongly developed breath-drawing pip noise and the sideways swaying food-begging posture in the Galah, aligns this species with other members of Cacatua which share these common traits, supporting the view of Adams et al. (1984) that the Galah belongs in Cacatua. It should be noted, however, that the length of the begging call in the Galah is very short, and in this respect approximates that of the Gang-gang and Cockatiel. The head-bobbing food-begging posture is probably genetically homologous in the Gang-gang and Cockatiel, and the closeness of these cockatoos is further demonstrated by their unique possession of grey, barred plumage and the series of pale spots on the undersurface of the wings in females. Their head-bobbing food begging posture resembles that of platycercine and polytelitine parrots, and may represent a primitive condition, in agreement with the view of Adams et al. (1984) that these two cockatoo species may be the most 'primitive'. The possession of a straight wheezing begging call, and also of the juvenile food-swallowing vocalisation AUSTRALIAN 248 COURTNEY BIRD WATCHER (among other characteristics as well, Courtney 1974), appear to firmly establish the Cockatiel as a cockatoo. Perhaps the most atypical species of the genus Cacatua is Major Mitchell's Cockatoo, which differs from all others in characteristics of juvenal down and in the forward, not sideways, sway of the begging posture (Courtney 1993). The rasping begging call and possession of the food-swallowing vocalisation in white-tailed and yellow-tailed black-cockatoos, in contrast with the squeaking begging call and lack of the food-swallowing vocalisation in the two red-tailed black-cockatoos, points to a natural division within the genus Calyptorhynchus, supporting the retention of two subgenera Zanda and Calyptorhynchus respectively, for this genus. The true function of the cockatoo food-swallowing vocalisation remains to be established. Pidgeon (1981) suggested that the jerking movement of the head may cause a modulation of the food-begging call, which thus may merely be an extension of the begging call. He went on to state that the call may stimulate the parent to maintain contact or to regurgitate, or it may have a social implication for other members of the family group. This suggests a behavioural or social function for the vocalisation, yet it seems equally likely that it may have a more direct and practical function. It would seem possible that air is being expelled rather than inhaled while food is being swallowed, otherwise accidental choking could result. The violent head-jerking movements associated with the transfer of food may be sufficient to cause choking. It is perhaps to guard against this risk that there is a need for expulsion of air in sufficient volume to create the sound. Thus, the actual sound itself may be functionless and simply part of an anti-choking process. Another explanation is that it is a rapid breath-drawing noise, synchronised between swallowing. Interestingly, Rowley (1990) observed that adult Galahs also utter this vocalisation when feeding their young, and R. Low (in litt. 1990) has heard a Cacatua galerita triton utter this call from within the egg, in an incubator, on the day before hatching. Why most cockatoos, and not other parrots, are compelled to jerk the head so violently when feeding young is not clear. Regardless of the function of this vocalisation, it must be noted that it occurs in all five cockatoo genera today, and so must have been a feature of early ancestral stock. The presumed loss of this trait in the Glossy and Red-tailed Black-Cockatoos, after such an immense span of time, is therefore rather more significant than is at first apparent. That a truly immense span of time is involved in cockatoo evolution now seems beyond doubt, with the discovery at Riversleigh, Qld, of a 20-million year-old upper mandible of a cockatoo (Boles in Smith 1991, Boles 1993, Archer et al. 1994). Courtney (1974) suggested that the black and the white cockatoos arose from a grey ancestor by simple intensification of grey pigmentation to produce the former, and conversely reduction and loss of grey to establish the latter. There is now an alternative possibility, going not from grey to black and white, but from black, to grey, to white. As the nestling plumage of Calyptorhynchus is much more intensely black than that of the adults (pers. obs., this study), this may mean that this genus did not evolve from a grey ancestor, for had this happened, then in all probability the young would be less black than the adults. Neither theory above conflicts with the belief that white cockatoos arose from a grey ancestor, and biochemical data (Adams et al. 1984), cranial details, and grey colouring in juvenile plumage of white cockatoos (Courtney 1974, 1985, 1993) support this supposition. Acknowledgements The following gave freely of their time in preparing sonagrams and for this I am most grateful: VOL. 16 (6) JUNE 1996 Juvenile Cockatoo Vocalisations 249 the late William R. Eastman Jr of University of Wyoming, U.S.A.; Messrs Norman Robinson and Bob Ashman of (then) CSIRO Division of Wildlife Research, W.A.; Dr Richard Zann and Ms Liz Tanger of LaTrobe University, Victoria; and Dr Denis Saunders of CSIRO Division of Wildlife and Ecology, W.A. Mr A.C. 'Sandy' Hunt placed at my disposal his knowledge, his birds and his ornithological library, of which I am most appreciative, and without which this study would not have eventuated. During the 42 years of this study, many people gave vital support in many ways, and I thank them all. I give special thanks to Mervyn Goddard, Wayne Wilcox, Ray Mcinnes, John Young, Clarrie Young, Judy Hunt, Jack Crisp, Beth Eastman, Drs Darryl Jones and Richard Noske, Sue Noske, Neville and Enid Connors, Brendan Lepschi and Julianne Farrell. 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