Social behavior of the ruff Philomachus pugnax (L.)

INTRODUCTION A. SCOPE OF THE STUDY The Ruff, Philomachus pugnax(L.), differs from other waders in its breeding behavior: courtship and mating take place on a communal display ground or lek; no sounds are uttered during these activities; nesting behavior, incubation, and parental care are the exclusive task of the female. The Ruff is also distinguished by its sexual dimorphism in both size and plumage, and by the extreme individual diversity in the male nuptial plumage. The earliest published accounts of behavior on the lek are those of SELOUS (1906, 1907), a pioneer in the field study of bird behavior. Interested in the Darwinian concept of sexual selection, SELOUS objectively described the interactions among the individual males and females on the lek in an attempt to gather information on partner choice on the lek and, specifically, on the function of figh6ng among the males. His descriptions and interpretations of this behavior are remarkably good considering the date at which they were made. Other accounts of field studies on the breeding behavior of the Ruff have since been published (PORTIELJE 1931; ANDERSEN 1944, 1948, 1951; LINDEMANN 1951; BANCKE & MEESENBURG 1952, 1958; MILDENBERGER 1953), and a number of authors have made comments on different aspects of the Ruff's breeding behavior (e.g., CHRISTOLEIT 1924; ARMSTRONG 1947; TINBERGEN 1959; WYNNE-EDWARDS 1962). VAN OORDT and JUNGE (1934, 1936) have investigated the endocrinological aspects of the development of the male nuptial plumage. LINDEMANN (1951) and GOETHE (1953) describe and comment on the extent of the plumage diversity among the males. The present study extends the observations on the lek behavior and morphological features in the external appearance of the Ruff. Specifically, this is an ethological study of the lek behavior of the Ruff which investigates the social organization of the lek community and the behavior patterns that serve mutual communication among the birds. It is assumed that the behavior patterns provide many clues for the understanding of the social organization. Further, particular attention is paid to the biological significance of the plumage diversity within the lek community. Accidentally, this study revealed that the Ruff presents an extreme example of behavioral polymorphism: it appears that within the male community two groups of males coexist which show distinct differences in behavior. In a complicated way these behavioral differences are associated with differences in the external appearance of the individual males. This paper is organized in the following manner. Descriptive data on morphologicai features in the external appearance of the Ruff are presented in Chapter II. Mutual relations within the male community, correlations of behavioral differences with external appearance, and the intersexual relations during courtship are dealt with in Chapter III; the typical situations on the lek in which the behavior patterns occur are also described in this chapter. Detailed descriptions of the form of these behavior patterns are presented in Chapter IV. Chapter V is concerned with a discussion of different aspects of the behavioral polymorphism and the plumage diversity in the male Ruff. ... Zie: Introductio