British VOLUME 72 NUMBER 12 DECEMBER 1979

What is the function of the little-known head movements performed by after diving? Differences in the actions of similar could aid identification rinzinger (1974) described and figured an enigmatic 'breast-looking' Pmovement ('das Vor-die-Brust-Schauen') of the Black-necked nigricollis, the function of which he could not determine even though observing it at close range. Shortly after emerging from an underwater dive, individuals of this species were seen to bend the neck slightly backwards and nod the head downwards so that the tip of the bill pointed towards the breast. Similar behaviour by Little Grebes ruficollis was also observed. Although the extent to which the bill actually contacted the breast was not made clear by Prinzinger, the behaviour is clearly related to what I have called 'throat-touching' (Simmons 1964, 1970), suggesting that it drains surplus water from the bill. This behaviour has recently been described in some detail for the P. cristatus (Simmons 1977); although the grebes (Podicipedidae) have been increasingly studied in recent years, I know of no other references to throat-touching in the ornithological literature, though I have myself seen the same or equivalent actions performed by Pied-billed Grebe podiceps, , Black-necked Grebe, Slavonian Grebe Podiceps auritus, Red-necked Grebe P. grisegena and, on film, occidentalis. A summary of these observations follows below for each species.

[Brit. Birds 72:563-569, December 1979] 563 564 Throat-touching by grebes Great Crested Grebe Podiceps cristatus Throat-touching is a common comfort-movement of both adult and young of this species, but can easily be overlooked because it is done so rapidly: the lowers its head to press the bill-tip momentarily on the lower part of the foreneck (see fig. 1) and then raises the bill again; the whole movement lasts less than a second. Occasionally, the bill does not quite contact the neck, and I call this incomplete movement a 'head-nod'. The Great Crested Grebe throat- touches in a variety of situations but especially after a dive or during pauses in surface-hunting with the head submerged, in both cases more or less immediately after it surfaces or raises its head from the water. The throat-touching often follows—or may be followed by—a lateral head-shake (another comfort-movement). Frame-by-frame analysis of film has confirmed my long-held impression that the throat-touch drains surplus water from the tip of the bill where it has collected in a large droplet. This appears to be the primary function of the behaviour; in certain other circumstances, however, it seems to be merely a response to irritation and other peripheral stimulation on the bill when it is dry (e.g. during preening). For further information on this and other comfort behaviour of the species, see Simmons (1977).

Fig. 1. Great Crested Grebe Podiceps cristatus throat-touching, drawn from 16-mm film (24 frames per second), with frame count indicated by figures (R.J. Prytherch)

Little Grebe Tachybaptus ruficollis Throat-touching by this species was not mentioned by Bandorf (1970) in his monograph, but is extremely common, probably more so than in the case of the Great Crested Grebe. 1 have observed it frequently, together with head-shaking, from both adults and downy young, mainly just after a dive, but also after the eating of tiny or the adding of weed to the nest-platform (in which similar circumstances the Great Crested Grebe also throat-touches). The movement is performed even more quickly than by the larger species, with a rapid down press of the bill (see fig. 2) lasting about one-eighth of a second and an almost instant recovery. At least after diving, Little Grebes may sometimes head-nod instead of full throat-touching; or one or two head-nods may follow a full throat-touch. It was this head-nodding, presumably, that Prinzinger (1974) described; I must emphasise, however, that—unlike the Black-necked Grebe (see further, below)-—the Little Grebe performs full throat-touching far more frequently.

Fig. 2. Little Grebe Tachybaptus ruficollis throat-touching, drawn from 16-mm film (24 frames per second), with frame count indicated by figures {R.J. Prytherch)

Pied-billed Grebe Podilymbus podiceps So far as I know, there is no mention of throat-touching by this American species in the literature. Judging, however, from observations on the vagrant at Chew Valley and Blagdon Lakes, Avon, in 1966 and 1968 respectively (Ladhams et al. 1967; Simmons 1969). the behaviour is not only very common but more conspicuous than that of any other grebes known Throat-touching by grebes 565 to me. Though performed quite quickly, the throat-touch looks more deliberate and exag­ gerated: the downward movement on the head develops into a marked bill-tucking action, probably due mainly to the shortness and thickness of the bill, the bird thus briefly pressing the tip of its bill against its foreneck before returning its head to the horizontal position. Throat-touching, with head-shaking, occurs immediately after a dive and during surface- hunting; also, but apparently mainly without head-shaking, during preening, not only when the bill is wet but also when it is dry. As with the Great Crested Grebe, throat-touching was seen when the bird was inactive or just swimming along; and once after a wing-flap, once after eating tiny prey, and once (along with other comfort behaviour) when it appeared to sufler from intense irritation on the bill. As again with the larger species, throat-touching was rare during the main phases of bathing, even intense dive-bathing. In 1968, I listened to over 950 songs of the Pied-billed Grebe and was able to observe the bird calling on a number of occasions as it adopted the characteristic song-posture (described and figured in Ladhams et al. 1967) in which the head is often tossed up and lowered close to the water surface. On some occasions, the grebe throat-touched immediately it stopped singing; it may well have some­ times dipped the bill in the water while singing, though I was not absolutely certain that it did. The Great Crested Grebe will throat-touch while threatening in a somewhat similar posture in which the bill definitely is often emersed.

Fig. 3. Pied-billed Grebe Podilymbuspodiceps throat- touching (R.J. Prytherch)

Western Grebe Aechmophorus occidentalis I have not seen this American species in life, but noted throat-touching, just after they had surfaced from a dive, by birds in a film by Prof. Robert W. Storer at the XIV International Ornithological Congress in Oxford in 1966.

Slavonian Grebe Podiceps auritus Throat-touching was not included among the comfort behaviour described for this species by Woolfenden (1956) and Storer (1969). In Inverness-shire, during June 1966, I observed several individuals and found throat-touching (and head-shaking) to be frequent after dives, when either one or the other movement occurred or, more usually, the sequence head-shake followed by throat-touch (or sometimes the reverse). This was confirmed from a lone bird at Chew Valley Lake in January 1968. It was also seen to throat-touch after eating a tiny fish and once, following a brief spell of dive-hunting, it throat-touched twice, 'dip-shook' a few times (i.e. dipped the bill in the water and head-shook), and then preened with some further throat-touching and frequent head-shaking. On another occasion, while surface-hunting, it head-shook and preened laterally after raising the head from below the water.

Fig. 4. Slavonian Grebe Podiceps auritus throat- touching (R.J. Prytherch)

Black-necked Grebe Podiceps nigricollis This is the first of two species which differ significantly from those described so far in this paper. My close-quarter observations on the Black-necked Grebe were limited to three separate individuals at Chew Valley and Blagdon Lakes in 1966 and 1968. On checking the first bird, I was immediately puzzled: it was clear that lateral head-shaking was the typical comfort-movement after a dive, and no full throat-touching was seen. The grebe did, however, perform infrequent nodding-type movements of the head, lowering the bill sharply so it pointed vertically downwards. The second individual behaved similarly: it usually head- 566 Throat-touching by grebes shook after surfacing (or surface-hunting), quite often following this with a jerky movement resembling a head-nod, sometimes right into the water—after which it head-shook again; at times, it also immediately preened dorsally near the shoulder or elsewhere after emerging from its dive. After dozens of dives, it may perhaps have throat-touched more fully only two or three times. On one date, I was able to compare the behaviour of the second bird with that of the vagrant Pied-billed Grebe: the Black-necked performed fewer post-diving comfort-movements of any sort, and then chiefly head-shakes with occasional abrupt head-nods. The third bird of this species usually just head-shook after repeated dives; it appeared to throat-touch just once. The down-nodding movement of the Black-necked Grebe—evidently the 'breast-looking' of Prinzinger (1974)—seems to be somewhat more deliberate and stereotyped than the similar head-nodding of some of the other species discussed earlier. I term it the 'head-bob', therefore, to distinguish it. The head-bob clearly has the same primary function as throat-touching of ridding the bill of surplus water, which, in this particular grebe, shows up conspicuously as an accumulated droplet on its distinctively flattened gonys. Throat-touching itself is. at best, rarely performed by Black-necked Grebes and may not exist at all for. as in the case of the Red-necked Grebe outlined below, there is the distinct possibility of confusion with similar- looking movements.

Fig. 5. Black-necked Grebe Podkeps nigricollis head bobbing (R.J. Prythtrch)

Red-necked Grebe Podkeps grisegena No mention of throat-touching was made by VVobus (1964) in his monograph of this species and my own observations indicate that, at best, as with the Black-necked Grebe, the behaviour is rare. During 14 hours of close watching of a pair in Denmark in June 1967, I established the following: (1) the grebes seldom if ever throat-touched after diving or when surface-hunting; (2) instead, they usually only head-shook (once, sometimes twice) to dispel the water that ran down the bill and collected on the gonys, or, less frequently, head-shook and then preened dorsally, often near the shoulder; (3) on a few occasions, they preened Iron tally on the lower foreneck, did a head-bob (in the manner of the Black-necked Grebe), or dipped the bill in the water instead; (4) on four occasions, they seemed to do a full throat-touch, but could more likely have been performing one of the movements just mentioned above; (5) no throat- touching was seen for certain during preening, not even after the bill got wet during ventral preening or head-scratching, though one bird did dip-shake; instead, they usually either head-shook or preened, or did both; (6) no throat-touching was seen cither in some other situations in which the Great Crested Grebe throat-touches: in the rain, after eating little fish. after eating a feather, or after mandibulating nest-material.

Fig. 6. Red-necked Grebe Podkeps grisegena bill- draining by preening (R.J. Prytherch)

In September 1969, at Cheddar Reservoir, Avon, I watched an immature Red-necked Grebe for over seven hours. It never throat-touched, neither after a dive nor while surface- hunting, preening or head-scratching. After surfacing, it usually did a head-shake; sometimes. this was followed sooner or later by dabbing the bill in the water (bill-dipping), by submerging the bill and part of the head (peering, as during surface-hunting), or, less often, by preening. After this, it tended to remain inactive during the rest of the pause between dives, though sometimes it did another head-shake, or an odd preen, or peered under the water. The head-shaking consisted of a marked lateral jerk, which seemed often to be a more forceful movement than the standard head-shake of the other grebes studied; in the case of the Red-necked Grebe, it appears largely to replace throat-touching, head-nodding and head- bobbing. Independent confirmation comes from Robin Prytherch (in litt.): he watched an Throat-touching by grebes 567 immature actively diving for 30 minutes on Kenfig Pool, Mid Glamorgan, in September 1977, and was surprised to see only head-shaking when he would have expected throat-touching (which he knows from the Great Crested, Little, Pied-billed, and Slavonian Grebes).

Discussion and summary The five main methods used by grebes to dispel water from the bill fall into two classes: (1) head-shaking and (2) bill-draining movements, composed of throat-touching, head-nodding, head-bobbing, bill-dipping and preening. These may be compared with the methods we use to remove surplus ink from a pen-nib before writing. We may then: (a) wave or jerk the pen sideways (equivalent to head-shaking); (b) touch the point against another object, such as the ink-well (throat-touching); (c) flick it sharply downwards with an abrupt stop (head-nodding, head-bobbing); (d) touch the droplet of ink against the surface of the reservoir of ink remaining in the well (bill-dipping); or (e) rub it on a cloth or similar object (preening). So far as we know, all grebes remove at least some of the surplus water from both head and bill by head-shaking; some—including the Great Crested, Little, Pied-billed, Slavonian and Western—then drain away the rest mainly by throat-touching. The Black-necked Grebe, however, which rarely if ever throat-touches, dispels the remaining water largely by head- bobbing (a more efficient version of the head-nodding movement of some or all of the species already mentioned, in which it seems to be an incomplete throat-touch). At least occasionally, the Black-necked Grebe also drains away water from the bill by bill-dipping and by preening. Bill-draining by preening, however, seems to be rather a speciality of the Red-necked Grebe, which rarely if ever throat-touches, though it will head-bob and bill-dip. For this species too, lateral head-shaking appears to play an even more important role in ridding the bill of surplus water than for the other species observed. The peering behaviour of the immature Red-necked Grebe at Cheddar Reservoir may have represented an extreme form of bill-dipping, perhaps through the process of postural facilitation (the two movements sharing the same initial action). Observations on this bird might suggest that the bill-draining movements are learned by the Red-necked Grebe, at least to some extent: it mainly head-shook and bill-dipped, whereas adults watched in Denmark mainly head-shook and preened. Head-bobbing, however, is performed by the downy young of the Black-necked Grebe (see figure in Prinzinger 1974) and is probably innate, as the throat-touching of the Great Crested (Simmons 1970) and Little Grebes certainly is. The bill-draining method could be a useful ancillary field character in the cases of certain grebes which afford identification problems in non-breeding plumage under poor conditions of observation. Thus, among Palearctic species, a smallish black-and-white grebe that throat-touches habitually would be a Slavonian not a Black-necked; similarly, a winter Great Crested might at times be distinguished from a winter Red-necked on the same basis. The whole topic of throat-touching and equivalent bill-draining behaviour of the grebes requires further study. We need information from more species—including those in the genera (golden grebes), 568 Throat-touching by grebes Lymnodytes* (Least Grebe), and (hoary-headed grebes)—and comparative data from other taxonomic groups of waterbirds. So far as I can judge, throat-touching is unique to the Podicipedidae. The closely convergent but unrelated divers (Gaviidae) do not appear to do it, nor do any diving seabirds, including the Brown Booby Sula kucogaster which I have studied intensively, nor the ducks (Anatidae) on which I worked professionally during 1970-73. Lateral head-shaking (with the bill inclined somewhat down) or latero-vertical head-flicking would appear to be the main response by ducks to water on the head and bill (see McKinney 1965); I recently confirmed this for surfacing Tufted Ducks Ayihya fuligula and Goldeneyes Bucephala clangula, though such movements seem to be relatively infrequent. The evolutionary development of throat-touching in the Podicipedidae is not fully clear. Thev behaviour is obviously much more specialised than the head-shaking that the grebes share with most or all other waterbirds. As throat-touching is absent or rare in the cases of some of the grebes themselves, it may have been derived from the head-nod, possibly via frontal preening of the foreneck. The head-nod itself may have evolved from bill-dipping and, in turn, given rise to the head-bob.

Acknowledgements My work at the Avon lakes in 1966-70 was supported by the Nature Conservancy and later by the Natural Environment Research Council. Full acknowledgements were given elsewhere (Simmons 1970, 1974). In connection with the present paper, I should like to thank Robin Prytherch for his line-drawings. Dr Mathilde Schommer kindly translated part of Prinzinger (1974) forme.

References BANDORF, H. 1970. Der Zwergtaucher. Die Nate Brehm-Bucherei 430. LADHAMS, D. £., PRYTHERCH, R. J., & SIMMONS, K. E. L. 1967. Pied-billed Grebe in Somerset. Brit. Birds 60: 295-299. MCKINNEY, F. 1965. The comfort movements of Anatidae. Behaviour 25: 120-220. PRINZINGER, R. 1974. Untersuchungen fiber das Verhalten des Schwarzhalstauchers Podiceps n. nigricellis, Brehm (1831). Anz- Om. Ges. Bayem 13: 1-34. SIMMONS, K. E. L. 1964. Feather maintenance. In THOMSON, A. L. (ed.) A New Dictionary of Birds, pp. 278-286. London & Edinburgh. 1969. The Pied-billed Grebe at Blagdon Lake, Somerset, in 1968. Bristol Om. 2: 71-72. 1970. The biology of the parent-chick stage in the Great Crested Grebe Podiceps cristatus. PhD thesis, University of Bristol. 1974. Adaptations in the reproductive biology of the Great Crested Grebe. Brit. Birds 67: 413-437. 1977. Further studies on Great Crested Grebes. 2. Maintenance activities and routine. Bristol Om. 10:175-196. STORER.R.W. 1969. The behavior of the in spring. Condor 71: 180-205.

*I cannot agree with my good friend Prof. R. W. Storer (1976, Trans. San Diego Soc. Nat. Hist. 18: 113-126) that the new-world Least Grebe should be put with the old-world dabchicks in the Tachybaptus, a course recently followed by Prof. K. H. Voous, rather incautiously in my opinion (1977, List ojRecent Holarctic Bird Species). As it certainly does not belong in Podiceps either, I believe the Least Grebe is best placed in a genus of its own between Tachybaptus and the hoary-headed grebes Poliocephalus. with both of which it shares certain character states, the name Lymnoaytes Oberholser, 1974, being available. This practice maintains the trend indicated by Simmons (1962, Bull. BOC 82: 109-116) towards the use of small genera as the best means of showing relationships within the family Podicipedidae. Throat-touching by grebes 569 WoBl'S, U. 1964. Der Rothalstaucher. Die New Brehm-Biicherei 330. Wooi.KKNDKN, G. E. 1956. Preening and other behavior of a captive Horned Grebe. Wilson Bull. 68: 154-156.

DrK. E. L. Simmons, Department of Psychology, The University, Leicester LEl 7RH