Studies on the Organisation of Bird Behaviour PETER JAMES
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Studies on the Organisation of Bird Behaviour PETER JAMES BRAMWELL SLATER Doctor of Science University of Edinburgh 1982 0J) 1 CONTENTS Page Declaration Acknowledgements iv Abstract V Introduction Vii Submitted papers, in chronological order, each numbered on its front page for reference SLATER, P.J.B. & OLLASON, J.C. 1972. The temporal pattern of behaviour in isolated male zebra finches: transition analysis. Behaviour 42: 248-269. SLATER, P.J.B. 1973. Describing sequences of behavior. IN: Perspectives in Fthology, P.P.G. Bateson & P.H.Klopfer, eds. pp. 131-153. Plenum Press, New York. OLLASON, J.C. & SLATER, P.J.B. 1973. Changes in the behaviour of the male zebra finch during a twelve-hour day. Animal Behaviour 21: 191-196. SLATER, P.J.B. '1974a. Bouts and gaps in the behaviour of zebra finches, with special reference to preening. Revue du Comportement Animal 8: 47-61. SLATER, P.J.B. 1974b. The temporal pattern of feeding in the zebra finch. Animal Behaviour 22: 506-515. SLATER, P.J.B. 1974c. Temporal patterning and the causation of bird behaviour. IN: Neural and Endocrine Aspects of the Behaviour of Birds, P. Wright, P.G. Caryl & D.M. Vowles, eds. pp. 11-33. Elsevier, Amsterdam. SLATER, P.J.B. & WOOD, A.M. 1977. Does activation influence short-term changes in zebra finch behaviour.? Animal Behaviour 25: 736-746. SLATER, P.J.B. 1979. A simple model for competition between behaviour patterns. Behaviour 67: 236-258. .1.1 SLATER, P.J.B. & INCE, S.A. 1979. Cultural evolution in chaffinch song. Behaviour 71: 146-166. INCE, S.A., SLATER, P.J.B. & WEISMANN, C. 1980. cnges with time ii the songs of a population of chaffinches. Condor 82: 285-290. SLATER, P.J.B., INCE. S.A. & COLGAN, P.W. 1980. Chaffinch song types: their frequencies in the population and distribution between the repertoires of different individuals. Behaviour 75: 207-218. SLATER, P.J.B. 1981. Chaffinch song repertoires: observations, experiments and a discussion of their significance. Zeitschrift fur Tierpsychologie 56: 1-24. SLATER,,-P.J.B. & INCE, S.A. 1982. Song development in chaff inches: what is learnt and when ? This 124: 21-26. SLATER, P.J.B. & CLEMENTS, F.A. 1981. Incestuous mating in zebra finches. Zeitschrift fur Tierpsychologie 57: 201-208. SLATER, P.J.B. & LESTER, N.P. 1982. Minimising errors in splitting behaviour into bouts. Behaviour 79: 153-161. SLATER, P.J.B. In press. Bird song learning: theme and variations. IN: Perspectives in Ornithology (Centennial Volume of the American Ornithologists Union), G.H. Brush & G.A.-Clark, Jr., eds. Cambridge University Press, New York. SLATER, P.J.B. In Press. Sequences of song in chaffinches. Animal Behaviour. Note: While the papers are numbered and bound in chronological order, it would be most appropriate to read paper 15 between papers 6 and 7, and paper 17 between paper 8 and paper 9. iv ACKNOWLEDGMENTS It is a pleasure to thank those who have contributed, both directly and indirectly, to the work contained in this thesis, especially my co-authors. Each of the individual papers acknowledges the help of others who have played a part in improving them. All the work included has been carried out at the University of Sussex and I should like to thank my colleagues in the Ethology and Neurophysiology group there for providing an extremely stimulating research environment. In addition I owe a special debt of gratitude to Professor Aubrey Manning, whd first fired my interest in animal behaviour while I was in Edinburgh, and Professor Richard Andrew, from whose insights I have gained enormously. Finally, I am grateful tothe Science Research Council for the four grants which have helped to finance this work (1970-1973; 1974-1977; 1977-1979; 1980-1982), and to the Royal Society for the award of an equipment grant (1981). ABSTRACT This thesis includes papers in two main areas oi bird behaviour: studies of temporal patterning and studies of song. These involve diverse approaches and findings which are drawn together by an introduction providing a guide to the individual papers and their main results. The papers on temporal patterning are mainly concerned with the behaviour of zebra finches. The distribution in time of individual behaviour patterns and their sequential relationships are described using techniques for analysing sequences and bouts of behaviour developed by the author. The rules underlying the patterning in time of feeding and preening are described in some detail. The occurrence of short-term rhythms of behaviour, changes within which match those in the daily cycler suggested that a single underlying variable might influence the occurrence of different behaviour patterns. However, this hypothesis was rejected following experimental manipulation of the short-term rhythms using cycles of sound and of light intensity. Instead, the results suggest that the sequential relationships found might result simply from competition between the behaviour patterns involved, an idea which computer simulations show to be plausible. A final paper on this topic concerns song in chaffinches and shows that, as with broader categories of behaviour in zebra finches, competition is an important factor in determining sequences of song types. The remaining papers on bird song involve both laboratory and field work, largely on chaffinches. Hand-rearing experiments show that young male chaffinches can learn complete songs either as fledglings or in the following spring; learning is normally extremely accurate but sometimes involves errors. • The frequencies of different song VI types and their distribution in the wild fit in well with these characteristics of learning, and it is argued that both local and geographical variation in song, as well as the way it has been found to change with time within a population, are simply a functionless byproduct of vocal learning. Possible reasons for sang learning, and for the occurrence of song repertoires, have been explored and are discussed in relation to work on the chaffinch and on other species. Laboratory work on zebra finches suggests that learning is unlikely to lead song to provide a measure of kinship: the results of mate choice experiments show birds to prefer mating with a relative rather than a stranger, but these preferences are more likely to be based on plumage differences than on song. vii INTRODUCTION This thesis includes a selection of papers falling into two main fields: studies on the temporal patterning of behaviour and studies of bird song, with special reference to its development and cultural evolution. Such a diverse range of topics, involving observations and experiments in both field and laboratory, as well as some theoretical work using computer simulation, may be unusual within a single thesis. It is the aim of this brief introduction to provide a framework which will help to draw the papers together and may be used as a guide through them. The introduction is subdivided into the two main areas of the thesis. Papers included in the thesis are referred to by their reference numbers, by which they are labelled in the contents list and ontheir covers: other references are listed at the end. Studies of Temporal Patterning The past ten years have seen a tremendous growth of interest in the quantitative analysis of behaviour. Prior tothàt:t:ime,:the quantitative methods used by ethologists had been very informally applied and were, quite often, misleading. This was excusable, because it is not at all easy to see how something as variable as behaviour should be quantified (Slater 1978). One area tha presented particular difficulties in this respect was that of temporal organisation. Generally speaking, animals only perform one behaviour pattern at a time, though they usually have a repertoire of many patterns which must vie with each other for expression. The aim of the papers on temporal patterning included in this thesis was to viii determine the rules which underlie the production of particular behaviour patterns at particular times. Quantitative treatment was essential to this and appropriate techniques had to be developed. Traditionally, two methods have been most commonly used to look at the temporal organisation of behaviour. One is sequence analysis, which helps to determine which behaviour patterns lead to one another or occur in association. The other is the analysis of the distribution of a single behaviour pattern in time as is, for example, often done in the study of meals and the intervals between them. Sequence analysis is applied in papers 1 and 17, and paper 2 provides a discussion of its application and a critique of its earlier usage, pointing out the hidden pitfalls of application and interpretation, many of which had previously gone unremarked. An especially important point raised here was the difficulty of interpreting sequence analyses which included transitions between a given behaviour and itself; paper 2 describes appropriate methods for avoiding this as well as consid- eration of transitions that cannot, by the nature of the animal or of its environment, occur. Papers 4, 5, 6 and 15 involve the analysis of the distribution in time of single behaviour patterns. Almost all behaviour occurs in bouts, many events of a given type occurring close together, while long intervals elapse without any events. For this reason, analysing behaviour in terms of bouts and the gaps between them has become a common technique. Just how useful it is, however, depends on the method used to define a bout. In the past the majority of studies used a criterion based on switching between behaviour patterns or on an arbitrary time interval, shorter gaps being considered as within a bout and longer ones as between bouts. The value of these :iX methods depends critically on whether the criterion selected matches up to the real organisation of the behaviour of the animal.