Kin selection may contribute to lek evolution and trait introgression across an avian hybrid zone

Understanding the mechanism(s) that favour cooperation among individuals competing for the same resources provides direct insights into the evolution of grouping behaviour. In a hybrid zone between golden-/yellow-collared (Manacus vitellinus) and white-collared (Manacus candei) manakins, males form aggregations composed of white and yellow males solely to attract females ('mixed leks'). Previous work shows that yellow males in these mixed leks experience a clear mating advantage over white males, resulting in the preferential introgression of yellow plumage allele(s) into the white species. However, the yellow male mating advantage only occurs in mixed leks with high frequencies of yellow males, and only a few of these males probably mate. Hence, it remains unclear why unsuccessful males join leks. Here, we used microsatellite markers to estimate pairwise relatedness among males within and between leks to test whether indirect genetic benefits of helping kin ('kin selection') can promote grouping. We found that yellow males are significantly more related to each other within than between leks, while relatedness among white males did not differ within and between leks. This suggests that yellow males may indirectly enhance their own reproductive success by preferentially lekking with relatives because yellow plumage is under positive frequency-dependent selection (positive FDS). Our results are consistent with the hypothesis that kin selection may promote grouping and facilitate positive FDS for yellow males, mediating the movement of yellow plumage across this hybrid zone.     

Social networks in the lek-mating wire-tailed manakin (Pipra filicauda)

How social structure interacts with individual behaviour and fitness remains understudied despite its potential importance to the evolution of cooperation. Recent applications of network theory to social behaviour advance our understanding of the role of social interactions in various contexts. Here we applied network theory to the social system of lek-mating wire-tailed manakins (Pipra filicauda, Pipridae, Aves). We analysed the network of interactions among males in order to begin building a comparative framework to understand where coordinated display behaviour lies along the continuum from solitary to obligately cooperative dual-male displays in the family Pipridae. Network degree (the number of links from a male to others) ranged from 1 to 10, with low mean and high variance, consistent with the theory for the evolution of cooperation within social networks. We also assessed factors that could predict social and reproductive success of males. Four network metrics, degree, eigenvector centrality, information centrality and reach, some of which assess circuitous as well as the shortest (geodesic) paths of male connectivity, predicted male social rise. The duration of a male's territorial tenure during the 4 years of the study predicted his probability of siring offspring.     

Loss of sexual dimorphism is associated with loss of lekking behavior in the green manakin Xenopipo holochora

Manakins (Pipridae) are well know for elaborate male sexual displays and ornate plumage coloration, both of which are thought to have evolved as a consequence of lekking breeding, the prevalent mating system in the family. Less attention has been paid to a handful of ‘drab’ manakin species, in which sexual dimorphism appears to be reduced or absent. Using character reconstruction, we show that these ‘exceptions to the rule’ represent phylogenetically independent cases of losses in sexual dimorphism, and as such could provide a focal group to investigate the link between changes in morphology and in life history (e.g. mating system). We take a first step in this direction by focusing on two subspecies of the putatively monomorphic green manakin Xenopipo holochlora to formally confirm that the species is sexually monomorphic in size and plumage color and test the prediction that sexual monomorphism is associated with the loss of lekking behavior in this species. Our results show that size dimorphism is present but limited in the green manakin, with substantial overlap in male and female morphometric measures, and that sexes are largely monochromatic (including from an avian perspective), despite marked coloration differences between subspecies. Behavioral observations indicate that males do not form leks and do not engage in elaborate sexual displays, that there is no stable pair bond formation, and that females provide parental care alone. These findings are consistent with the idea that changes in mating behavior may have driven changes in morphology in Pipridae, and we encourage similar studies on other drab manakins to better understand this relationship.     

Evolution of black grouse leks: female preferences benefit males in larger leks

Leks, communal display grounds in which males display and femalesonly attend to mate, represent one of the most remarkable outcomesof sexual selection. There have been no detailed studies thatcompare the behavior of males and females between leks of differentsizes to test if there is any benefit for male clumping andto test the many hypotheses suggested to explain lekking. Inthe black grouse, Tetrao tetrix, larger leks have many morefemale visits and copulations, leading to a higher average malemating success. Females visiting larger leks are also more likelyto mate, indicating that female preferences of males are importantfor the evolution of leks. Yearling males seldom copulate, buttheir presence on the lek increases the mating success of adultmales, suggesting that lek size per se and not only male qualityaffects female preferences for larger leks. The distributionof males over lek sizes agrees with a game theory model of idealfree distribution with unequal competitors, in which less competitivemales go to smaller leks.     

PHYLOGENETIC ANALYSIS OF THE EVOLUTION OF ALTERNATIVE SOCIAL BEHAVIOR IN THE MANAKINS (AVES: PIPRIDAE)

Phylogenetic analyses of lekking, lek spatial organization, and cooperative and coordinated lek display in the manakins (Aves: Pipridae) demonstrate that variation in social behavior in the group has a strong, phylogenetic component. Two of the three classes of social behavior examined also show significant phylogenetic constraints. Current adaptive plasticity models are insufficient to explain the phylogenetic variation in these behaviors in the manakins. These findings support the conclusion that vertebrate reproductive social behavior has an evolutionary history, and that it is not determined solely by adaptive individual plasticity to current conditions. The evolution of social behavior, particularly through sexual selection, can have historical consequences that can limit subsequent behavioral adaptation.     

UNIDIRECTIONAL INTROGREESION OF A SEXUALLY SELECTED TRAIT ACROSS AN AVIAN HYBRID ZONE: A ROLE FOR FEMALE CHOICE?

Hybridization can be an evolutionary creative force by forming new polyploid species, creating novel genetic variation or acting as conduits of potentially advantageous traits between hybridizing forms. Evidence for the latter is often difficult to find because alleles under positive selection can spread rapidly across a hybrid zone and sweep to fixation. In Western Panama, an avian hybrid zone between two species of manakins in the genus Manacus exists where the unidirectional introgression of bright, yellow plumage into a white population provides evidence for the importance of hybrid zones as conduits of advantageous traits. Several lines of indirect evidence suggest that sexual selection favoring yellow plumage drives this asymmetrical spread, but more direct evidence is lacking. Along the edge of the hybrid zone, both yellow- and white-collared manakins are found in the same mating arenas or leks and compete for the same females ("mixed leks"), providing us with a unique opportunity to understand the dynamics of yellow plumage introgression. We studied these mixed leks to determine whether yellow males have a mating advantage over white males and, if so, whether the mating advantage is driven by male-male interactions, female choice, or both. We found that yellow males mated more than white males, suggesting that sexual selection favoring yellow males can, indeed, explain the spread of yellow plumage. However, we found that this advantage occurred only in mixed leks where the frequency of yellow males is greater than white males. This suggests that the advantage of yellow males may depend on the presence of other yellow males, which may slow the rate of introgression in leks where yellow frequency is low such as in areas where yellow males are beginning to colonize the white population. This, along with the geographic barrier posed by major rivers in the hybrid zone, may initially limit or slow the spread of yellow plumage. Finally, we found that yellow and white males were similar in aggression and body size, and held comparable positions within leks. Because these traits or factors are often important in or dictated by aggressive male-male interactions, these comparisons indicate that male-male interaction is not the primary mechanism for the spread of yellow plumage. However, white and yellow males received similar numbers of courtship visits from females but differed in the number of matings, suggesting that females actively rejected white in favor of yellow males. Our results indicate that sexual selection by female choice has driven the unidirectional introgression of yellow plumage into the white population, providing a mechanism for how hybrid zones act as conduits of novel and advantageous traits.     

SEXUAL SELECTION THROUGH FEMALE CHOICE IN LAWES' PAROTIA,A LEK-MATING BIRD OF PARADISE

We studied sexual selection in Lawes' Parotia, a lek-mating bird of paradise, during 1981–1983 in Papua New Guinea. There was a high variance in mating success among males, with fewer than half of the individuals mating in any one year. This variance was independent of male-male interactions and disruptions. A role of female choice in sexual selection was suggested by the patterns of female visitation to courts and statistical correlations across males between phenotypic traits and mating success. Females repeatedly visited most males in their home ranges and began visiting males up to six weeks before mating. In one or more years, six aspects of male behavior and one morphological variable were positively correlated with mating success, but the probability values were not significant using a simultaneous inference test. Calculation of combined probability values across all three years revealed that one aspect of male display behavior, the probability of display, positively and significantly influenced mating status. The probability of display was also significantly correlated with relative mating success among males. Females showed strong fidelity to mates, both within and between seasons. Display sites of male Lawes' Parotia are variably dispersed, but mating success did not differ for grouped and solitary males. These data confirm an important role of female choice in sexual selection in birds of paradise but also suggest that female choice may be unrelated to the process of lek-initiation in this species.     

High-Speed Video Analysis Reveals Individual Variability in the Courtship Displays of Male Golden-Collared Manakins

The males of the Golden-collared manakin ( Manacus vitellinus ), a passerine bird of the Neotropical region, perform elaborate courtship displays that are among the most spectacular in the animal kingdom. During a 7-mo long breeding season, male manakins aggregate in leks of up to 12 individuals, and each male clears a small 'court' on the forest floor where he spends several hours per day performing his displays either with or without the presence of a female. Like males of other manakin species, males of M. vitellinus produce loud mechanical sounds with their wings during the displays. The elaborate displays of the manakins are thought to be the result of sexual selection, which is particularly intense in lekking species in which females choose their mate mainly on the basis of behavioural and morphological features. However, we know little about differences in display between male manakins which may be related to individual differences in reproductive success. A quantitative, detailed analysis of the courtship displays has been difficult because the birds' movements are too fast to be studied with standard video recording techniques. For the first time, we recorded the displays of male Golden-collared manakins in the forest of Panama with a high-speed camera that allows a time resolution 5–40 times higher than that of a standard video camera. We found that several elements of the displays differed significantly between individuals. In addition, the slow-motion analysis revealed the features of the displays that had not been described in previous studies. Individually different features of the displays may form the basis for female choice and will allow testing hypotheses about the evolution of the manakin displays by sexual selection and their importance for speciation mechanisms in the genus Manacus .     

Genetic structure among closely spaced leks in a peripheral population of lesser prairie-chickens

We evaluated the genetic structure of birds from four closely spaced leks in a peripheral population of lesser prairie-chickens (Tympanuchus pallidicinctus). Analyses of molecular variance revealed significant genetic structuring among birds from different leks for six microsatellite loci (FST = 0.036; P = 0.002), but we found no genetic differentiation at the mtDNA control region. Significant deviations from Hardy-Weinberg revealed an excess of homozygote genotypes within each of the leks studied (FIS = 0.190-0.307), indicative of increased inbreeding. Estimates of relatedness using microsatellite data suggest that the genetic structuring among lesser prairie-chicken leks occurs in part because of a lek mating system in which males at some leks are related. Structuring may also be caused by stochastic effects associated with a historical decline in population size leading to small, semi-isolated leks and high site fidelity by reproductive males. Results from this study suggest that microspatial genetic structuring may occur in lek-mating bird species with low levels of dispersal.     

Effects of avian malaria on male behaviour and female visitation in lekking blue‐crowned manakins

Avian malaria, the infection by blood parasites of the genus Plasmodium, can reduce host fitness not only through mortality, but also by impairing the expression of sexual selection traits. Although different studies highlight the association of parasitism with a decrease in host reproductive success, few studies have addressed the role of parasites in honest signalling by lekking species. Hence, it is still uncertain which fitness components are affected by parasites in these species. We investigated whether avian malaria is associated with a decrease in mating behaviour of male blue‐crowned manakins Lepidothrix coronata and whether it affects female visitation in leks of a population in the central Amazon. Through behavioural observations, we estimated the rates of total male activity and social interaction, as well as the frequency of female visits at individual perches. We then examined if individuals were infected with Plasmodium spp. using molecular techniques. Avian malaria was associated with a decrease in male mating behaviour in each lek, and mating behaviour correlated with female visitation. Although rates of social interaction were not correlated with avian malaria among males, we observed that interacting with several individuals within a lek may be advantageous for males, as they also vocalized and displayed more, thus increasing their chances of being visited by females. Although female visitation was not associated with avian malaria in individuals or leks, it is still possible that female visitation is indirectly affected by avian malaria through the latter's effects on male activity. We suggest a role for male activity as an honest sexual signal for females. Thus, male display rate could be used by females as cue for the probability of a male being infected.     

The displays of the White-throated Manakin Corapipo gutturalis in Suriname

The courtship displays of the White-throated Manakin Corapipo gutturalis (Pipridae) were observed in the Brownsberg Nature Preserve, Suriname, for over 50 h on 17 days between 17 October and 17 December 1982, and the display elements and calls are described. Males perform displays from perches in trees, in flight and on mossy fallen logs. The perch displays are performed as preliminaries to the log-approach displays which are given while in flight towards the log. The log-approach displays vary in length and complexity from a short flight from a nearby perch down to the log, to a dramatic flight above the canopy and back to the log. As males land, they perform a series of aerial manoeuvres and give a complex vocal and mechanical display call. Males may also perform a slower silent moth-flight log approach. The log displays are the culminating elements of courtship and copulation is known to take place there (Davis, T.A.W. 1949. Ibis 91: 146–147). All the courtship displays can be performed either solitarily by a single male or by a group of up to seven males which compete simultaneously for access to single display sites at a series of different logs. Fourteen display logs were located dispersed in two areas 250 m wide which were separated by 350 m, but it was not determined whether these areas constituted separate leks with different pools of possible mates. The behaviour of C. gutturalis is compared with that of the White-ruffed Manakin Corapipo leucorrhoa and other manakins. Male Corapipo appear to have abandoned defence of exclusive advertisement territories in favour of simultaneous competition for a series of different display sites. This detached or mobile form of lek is unique among known manakins and a mechanism for its evolution through female choice is discussed.     

Phylogenetic Analysis of the Evolution of Display Behavior in the Neotropical Manakins (Aves: Pipridae)

Phylogenetic systematic methods were applied in an investigation of the evolution of lek display behavior in the Neotropical manakins (Aves: Pipridae). Results of a previous investigation of the syringeal morphology of manakins were used as a behaviorally independent estimate of the phylogeny of the family. Three phylogenetic analyses of 44 display characters wer     

The resident's dilemma: a female choice model for the evolution of alternative mating strategies in lekking male ruffs (Philomachus pugnax)

Previous models for the evolution of alternative male matingbehavior have virtually ignored the role of female choice. Wepresent a model in which female choice favors the evolutionand maintenance of alternative mating strategies in male ruffs,Philomachus pugnax. Resident male ruffe establish and defendcourts on leks against other residents, while non-territorialsatellite males move between leks and among courts on a lek.Residents appear to actively recruit satellites to their courts,even though satellites may mate with females once there. Residentbehavior toward satellites and data on female behavior suggestthat residents benefit from a satellite's presence due to somefemale preference for mating on co-occupied courts. However,if all residents accept satellites, none gains any relativeadvantage, yet all pay the costs of having satellites on theircourt. We present a game theoretical model that shows that therelative nature of female choice places residents in an evolutionarydilemma with respect to satellite acceptance. Although all residentswould benefit if satellites could be cooperatively excludedfrom leks, the only evolutionarily stable strategy for individualresidents is to defect and accept satellites. The model alsodemonstrates that this "resident's dilemma" likely exists onlyin a local sense, since the failure of residents to cooperativelyexclude satellites from leks need not result in globally lowerpayoffs, due to frequency-dependent selection on the proportionof satellites in the population. Our analysis suggests thatthe resident-satellite relationship in ruffs, despite its obviouscompetitive elements, is fundamentally a cooperative associationfavored by female choice. Female choice has also been proposedas the primary mechanism selecting for male association to formleks in ruffe. In this context, resident-satellite associationsmay be thought of as transitory "leks within a lek     

Males in seemingly female‐like plumage do not mimic females: UV reflectance reveals temporal cryptic dimorphism in a manakin species exhibiting delayed plumage maturation

Manakins (Pipridae) are neotropical birds that usually exhibit delayed plumage maturation (DPM). Thus, while plumage of most adult male manakins is brightly conspicuous, subadult males and females are basically dull‐olive green. Although sexual dichromatism in some bird species may be evident only through UV reflectance, this phenomenon, known as hidden sexual dichromatism, has not been previously studied in manakins to compare subadult males and females. Within this framework, we carried out spectrophotometric analyses in searching for hidden sexual dichromatism in the white‐bearded manakin Manacus manacus, through comparison of UV spectra in females and subadult males in green plumage. Our results revealed UV reflectance in both sexes in green plumage. Moreover, we found UV spectral differences in homologous color patches between sexes, particularly at belly. Since the observed differences may allow intraspecific sex recognition of individuals in green plumage, our results do not support the female‐mimicry hypothesis to explain delayed plumage maturation in the white‐bearded manakin. Although our findings dismiss the female mimicry hypothesis, we cannot state whether these results support the non‐mutually exclusive cryptic and status signaling hypotheses. We propose then, that dull coloration of subadult males may serve both as a cryptic trait and to limit the energetic costs of acquiring the adult plumage before sexual maturity. Meanwhile, differential UV color traits between sexes in green plumage may allow adult males to avoid unnecessary energy expenditures in courtship displays in the presence of males near leks, and to selectively focus their the courtship displays on females. In accordance with the status signaling hypothesis, subadult males can be recognized both as males and subordinates and consequently may practice courtship displays without suffering aggressions by adult males. Our results highlight the importance to include a wider range of spectrophotometric information analyses for testing hypotheses regarding delayed plumage maturation.     

Evolution of ungulate mating systems: Integrating social and environmental factors

Ungulates exhibit diverse mating systems that range from monogamous pair territories to highly polygynous leks. We review mating systems and behaviors across ungulates and offer a new approach synthesizing how interacting factors may shape those mating systems. Variability exists in mating systems among and within species of ungulates and likely is affected by predation risk, availability of resources (food and mates), habitat structure, and sociality. Ungulate mating systems may be labile as a consequence of the varying strength of those interacting factors. In addition, degree of polygyny and sexual dimorphism in size are associated with the evolution of mating systems. Neither male–male combat nor paternal care, however, can completely explain differences in sexual size dimorphism for ungulates, a necessary component in understanding the development of some mating systems. Whatever the evolutionary pathway, sexual segregation limits paternal care allowing more intense male–male competition. Selection of habitat structure, because it modifies risk of predation, is a major determinant of sociality for ungulates. Likewise, ruggedness and steepness of terrain limit the types of mating systems that can occur because of limitations in group size and cohesiveness, as well as the ability of males to herd even small groups of females effectively. The quality and defensibility of resources affect mating systems, as does the defensibility of females. Population density of females also may be a critical determinant of the types of mating systems that develop. Size of groups likewise constrains the types of mating tactics that males can employ. Our aim was to use those relationships to create a broad conceptual model that predicts how various environmental and social factors interact to structure mating systems in ungulates. This model provides a useful framework for future tests of the roles of both ecological and social conditions in influencing the social systems of ungulates.     

DELAYED MATURATION,NEOTENY, AND SOCIAL SYSTEM DIFFERENCES IN TWO MANAKINS OF THE GENUS CHIROXIPHIA

Long-tailed manakins (Chiroxiphia linearis) and swallow-tailed manakins (C. caudata) are closely related, sexually dichromatic, lek-breeding species in which male mating success is highly skewed. Males of both species delay plumage maturation. Before reaching the definitive state, they wear a sequence of feather coats less conspicuous than that of the adult. Nondefinitive plumages probably enhance male survival in the two species; in C. caudata they may also enhance breeding success of young males, who may be fully reproductively mature their first year. In C. linearis testicular development is retarded along with that of plumage, although males may be physiologically capable of breeding prior to the acquisition of the definitive plumage. This difference probably reflects differences in the social systems of the two species. Five hypotheses have been proposed to explain the evolution of delayed plumage maturation. The sexual-selection, cryptic-breeder, and winter-adaptation hypotheses suggest that it functions primarily to enhance survival of young males. The juvenile- and female-mimicry hypotheses emphasize enhancement of immediate mating success. Support is provided for all but the female-mimicry hypothesis; it is argued that data are more consistent with juvenile mimicry and a neotenic origin of nondefinitive plumages.     

Lek fidelity and movement among leks by male Greater Sage‐grouse Centrocercus urophasianus: a capture‐mark‐recapture approach

Males in lek mating systems tend to exhibit high fidelity to breeding leks despite substantial evidence of skewed mating success among males. Although movements between leks are often reported to be rare, such movements provide a mechanism for an individual to improve lifetime fitness in response to heterogeneity in reproductive conditions. Additionally, estimates of apparent movements among leks are potentially biased due to unaccounted variation in detection probability across time and space. We monitored breeding male Greater Sage‐grouse Centrocercus urophasianus on 13 leks in eastern Nevada over a 10‐year period, and estimated movement rates among leks using capture‐mark‐recapture methods. We expected that male movement rates among leks would be low, despite predictions of low breeding success for most males, and that detection rates would be highly variable among leks and years. We used a robust design multistate analysis in Program mark to estimate probability of movements among leks, while accounting for imperfect detection of males. Male Sage‐grouse were extremely faithful to their leks; the annual probability of a male moving away from its original lek of capture was approximately 3% (se = 0.01). Detection probabilities varied substantially among leks (range = 0.21–0.95), and among years (range = 0.30–0.76), but remained relatively constant within years at each lek. These results suggest that male Sage‐grouse dispersal is either rare, or consists primarily of dispersal of sub‐adults from their natal areas prior to the breeding season. The study highlights the benefits of robust design multistate models over standard ‘live‐encounter’ analyses, as they not only permit estimation of additional parameters, such as movement rates, but also allow for more precise parameter estimates that are less sensitive to heterogeneity in detection rates. Additionally, as these data were collected using capture‐mark‐recapture methods, our approach to estimating movement rates would be beneficial in systems where radiotagging is detrimental to the study organism.     

Androgen and the elaborate courtship behavior of a tropical lekking bird

In most bird species, male courtship behavior is controlled by testosterone (T) and its metabolites. In species breeding in temperate and arctic regions T circulates at high levels during a relatively short courtship period because high levels of T can be costly in terms of immunocompetence and parental care. Few studies have investigated androgen modulation of courtship behavior in tropical birds. Male golden-collared manakins (Manacus vitellinus) aggregate in leks for several months and perform spectacular, acrobatic courtship displays. Here we examined whether T is elevated in golden-collared manakins during the displaying period and if courtship behavior is modulated by androgen action on androgen receptors. We measured T levels in displaying males at the beginning of the breeding season and again, one month later. In addition, both wild and captive males were treated with the anti-androgen, flutamide, and their courtship behavior was recorded for several weeks. T levels were relatively high shortly after leks were established but decreased substantially a month later, even though the amount of courtship did not change. Flutamide reduced male courtship activity for one week, but display behavior then increased after two weeks of flutamide treatment. Our studies show that androgens modulate male manakin courtship, but the amount of courtship is not directly correlated with the concentration of circulating T. These results suggest that the relationships between androgen and courtship might differ between tropical and temperate birds.     

Lekking without a paradox in the buff-breasted sandpiper

Females in lek-breeding species appear to copulate with a small subset of the available males. Such strong directional selection is predicted to decrease additive genetic variance in the preferred male traits, yet females continue to mate selectively, thus generating the lek paradox. In a study of buff-breasted sandpipers (Tryngites subruficollis), we combine detailed behavioral observations with paternity analyses using single-locus minisatellite DNA probes to provide the first evidence from a lek-breeding species that the variance in male reproductive success is much lower than expected. In 17 and 30 broods sampled in two consecutive years, a minimum of 20 and 39 males, respectively, sired offspring. This low variance in male reproductive success resulted from effective use of alternative reproductive tactics by males, females mating with solitary males off leks, and multiple mating by females. Thus, the results of this study suggests that sexual selection through female choice is weak in buff-breasted sandpipers. The behavior of other lek-breeding birds is sufficiently similar to that of buff-breasted sandpipers that paternity studies of those species should be conducted to determine whether leks generally are less paradoxical than they appear.     

Male signalling and lek attractiveness in the Mediterranean fruit fly

I tested the null hypothesis that females of the Mediterranean fruit fly, Ceratitis capitata, were equally likely to visit leks composed of males with high versus low mating success. In laboratory trials, the observed distribution of matings among males differed significantly from that expected by chance, owing primarily to the higher than expected numbers of individuals with low (mated 0-1 days over 6 consecutive observation days) or high (mated 4 or more days) mating scores. I termed these two groups as 'low' and 'high' maters, respectively. In the field, greater numbers of female sightings were made at artificial leks of high maters than low maters. This result apparently reflected a greater calling propensity among high maters. Slopes of female sightings versus calling level did not differ significantly between leks of low and high maters, suggesting that the observed relationship between calling activity and female sightings was independent of male mating status. Following the same protocol, I conducted a second experiment to examine whether males used the signals of conspecific males to locate lek sites and, if so, whether signal attractiveness varied with male mating ability. Attraction of males to calling conspecifics was far weaker than that observed for females, and over five different trials a total of only seven male sightings were made at any of the established leks. Copyright 2000 The Association for the Study of Animal Behaviour.