Goller, F. & Larsen, O.N. 1998. New views on sound generating mechanisms. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr., Durban. Ostrich 69: 216.

Direct examination of the avian vocal organ, the syrinx, is difficult during phonation. Models describing sound generation are therefore based on physiological observations, excised syrinx preparations, and theoretical studies. The "classical" models for songbirds and several non-songbird groups postulate that sound is generated by vibrations of thin membranes (e.g. medial tympaniform membranes - MTM). We studied the syrinx of songbirds and non-songbirds directly by filming it through an endoscope. Internal and external video images of the syrinx were recorded simultaneously with subsyringeal air sac pressure during spontaneous or brain stimulation-induced vocalisations. These endoscopic images identify a new sound source and imply a different phonatory mechanism. In preparation for phonation, soft tissue masses (medial and lateral labia in songbirds, lateral tympaniform membranes in pigeons) are moved into and close the syringeal lumen (actively and/or by increased subsyringeal pressure) and vibrations of these structures always accompany sound generation. In addition, the presumed sound generating membranes of the "classical" model (MTM in songbirds and pigeons) were disabled by either stiffening or complete rupture. Birds with disabled MTM were not only able to phonate, but also the vocalisations remained nearly intact, further supporting the new model of sound generation.

Key words: syrinx, endoscope, medial tympaniform membranes, lateral labium, song

Palleroni, A.R., Miller, P. & Yamaguchi, A. 1998. Individual and flock member recognition of distress calls in a socially-living monogamous galliform, Colinus virginianus. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr., Durban. Ostrich 69: 216.

Distress calls have been viewed as addressed primarily to predators rather than to companions, placing no special premium on individual caller recognition. Northern Bobwhite distress calls are found to display a high degree of individuality, being more acoustically diverse among than within individuals. Playbacks of distress calls demonstrated that they were individually recognised by mates, which responded more strongly to the playbacks than did other covey members, with significantly more aggressive postures and attacks towards the source speaker. When calls of two individuals were played simultaneously through different speakers, the mate of each responded selectively. Subjects also responded significantly more to distress calls of a covey member than to those of non-covey members. While distress calls of covey members are more potent than those of non-covey members, this is not the case for all call types. Playbacks reveal that with certain other calls (group movement calls, separation calls and unmated male calls) responses to non-covey member calls were greater than to calls of members of a bird's own covey. These results demonstrate that personal and group vocal recognition occurs in quail and may require some reassessment of the functional significance of distress calling in birds.

Key words: individual recognition, distress calls, quail, communication, alarm call

Buchanan, K.L., Catchpole, C.K. & Lodge, A. 1998. Does repertoire size indicate parasite resistance in the Sedge Warbler Acrocephalus schoenobaenus? In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr., Durban. Ostrich 69: 217.

Parasite-mediated sexual selection has attracted much interest in recent years. Convincing evidence for the association of heritable male resistance with pathogens and sexually selected male traits however, is sparse. During 1995 and 1996 breeding populations of Sedge Warblers were studied and blood sampled. A sample of song was recorded for all breeding males, for a measure of syllable repertoire size. The amount of time spent song flighting was quantified for each individual male. Analysis of the blood smears taken showed the presence of three types of haematozoan parasites in the population, Trypanosoma sp., Haemoproteus sp. and Plasmodium sp. In both 1995 and 1996 infected males had significantly lower syllable repertoire sizes than uninfected males. Furthermore, in 1996 infected males spent significantly less time song flighting before pairing. Both male repertoire size and the amount of time spent song flighting have previously been found to indicate male attractiveness. Infected males were also found to feed their offspring in the nest at significantly lower rates than uninfected males. Provisional results therefore suggest that repertoire size and/or song flighting effort may indicate male condition and therefore male parental quality. The possibility that such traits may also indicate heritable resistance however, cannot be discounted.

Key words: song, parasites, sexual selection, Hamilton-Zuk hypothesis, female choice

Jouventin, P. & Aubin, T. 1998. The acoustic basis of parental recognition by penguin chicks: Importance of environmental factors. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr., Durban. Ostrich 69: 218.

In the penguin species, chicks recognise their parents in the hubbub of the colony using mainly acoustic cues. The call an adult makes when seeking the chick is emitted in a context involving the noise generated by other individuals and the screening effect of the bodies. From their ability to recognise a particular call in this context, it is assumed that chicks use peculiar strategies of coding/decoding. We have studied these strategies by playing-back modified display calls to three species. One, the Adélie Penguin (AP) Pygoscelis adeliae, has a nest which serves as a meeting point; the King Penguin (KP) Aptenodytes patagonicus has a rendezvous site limiting the area to explore in the colony, and the Emperor Penguin (EP) Aptenodytes forsteri has no nest site and consequently has no possibility of using visual landmarks. All these species exhibit signals that are highly redundant in the temporal and frequency domains and have sharp amplitude changes which confer to the call a maximal locatability. According to the theory, two processes facilitate the detection of a signal embedded in the noise: the frequency-band analysis and the temporal analysis of amplitude or frequency modulations. Our experiments demonstrate that the vocal signature of the AP corresponds to the first process, the vocal signature of the KP to the second process and the vocal signature of the EP to a combination of both. The territorial habits and the environmental constraints should explain the differences observed in the strategies of coding-decoding of these species.

Key words: penguin, acoustic recognition, parent-chick recognition, colonality, seabird

Roberts, G., Harris, M.P. & Wanless, S. 1998. Reciprocal altruism among allopreening Common Murres Uria aalge. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr., Durban. Ostrich 69: 218.

There is great theoretical interest in the evolution of reciprocal altruism because it appears susceptible to cheating. However, there are few documented examples and there is much controversy. Murres allopreen their mates and neighbours at breeding colonies. We argue that this behaviour is an example of reciprocal altruism and use the system to test the assumptions and predictions of models of reciprocity. The study was conducted on the Isle of May, Scotland. Individually identifiable breeding murres were video-taped, and sequences of allopreening behaviour transcribed. Allopreening was found to be reciprocal, in that individuals both performed and received allopreens. However, over short time scales there was no correlation between giving and receiving. There was evidence that murres responded to the allopreening behaviour of other individuals. However, their behaviour did not conform to the predicted Tit-for-Tat pattern in which reciprocation is rewarded and non-reciprocation punished. Reciprocity was complicated by temporary asymmetries (off-duty birds allopreen more than brooders); differences in generosity (the duration and number of allopreens given); and the different forms of defection (failure to take an opportunity to allopreen or failure to respond to a solicitation posture). We conclude that the biology of real interactions differs from the assumptions and predictions of current models.

Key words: murres, allopreening, reciprocity, tit-for-tat, game theory

Hailman, J.P., Woolfenden, G.E. & Hailman, E.D. 1998. Avian gaits. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr., Durban. Ostrich 69: 219.

Remarkably little was known about terrestrial locomotion in birds. We studied (1) different gaits in the Florida Jay Aphelocoma coerulescens and (2) species differences in usual gait within the Corvidae. Speed of movement largely determines gait in the Florida Jay, which walks a few steps when moving slowly, mostly hops (quicker), and runs rapidly. Other corvids use all three gaits, but authorities agree on which is usual in a given species. Usual gait correlates almost perfectly with Goodwin's classification of foraging place: walkers forage only on the ground whereas hoppers forage both in vegetation and on the ground. Usual gait also correlates almost perfectly with size: walkers have larger body mass and longer tarsi than hoppers. The little-known ground-jays Podoces (four to five species) are the only usual runners, probably forage only on the ground, and have small body mass with long tarsi.

Key words: gait, locomotion, corvid, behaviour, anatomy