松墨天牛成虫对幼虫虫粪挥发性物质的触角电位反应及林间驱避试验

为了研制松墨天牛Monochamus alternatus Hope驱避剂,本文利用触角电位技术和田间试验的方法研究了松墨天牛雌雄成虫对幼虫虫粪挥发性物质的触角电位反应及幼虫虫粪己烷提取物、合成化合物混合物的林间驱避作用。结果表明：α-蒎烯、β-蒎烯、3-蒈烯、柠檬烯和长叶烯均能引起松墨天牛雌雄成虫一定的触角电生理反应,而4-甲基-2,6-二叔丁基苯酚不能引起松墨天牛雌雄成虫的触角电生理反应。林间驱避试验结果说明,幼虫虫粪的己烷提取物处理过的树干上的刻槽数明显少于对照树干上的刻槽数,二者具有极显著差异;有合成化合物的混合物存在的诱捕器诱捕到的雌虫数（平均值3.80±1.02）与对照诱捕到的雌虫数（平均值16.80±1.16）差异极显著。结果显示α-蒎烯、β-蒎烯、3-蒈烯、柠檬烯、长叶烯和4-甲基-2,6-二叔丁基苯酚的混合物对松墨天牛雌虫具有驱避作用,有望开发出一类新的驱避剂。     

Avoiding a compromise between sexual selection and species recognition: female swordtail fish assess multiple species-specific cues

Females increase their risk of mating with heterospecifics whenthey prefer the traits of conspecifics that overlap with traitsfound in heterospecifics. Xiphophorus pygmaeus females havea strong preference for larger males, which could lead to femalespreferring to mate with heterospecific males; almost all sympatricX. cortezi males are larger than X. pygmaeus males. In thisstudy, we show that X. pygmaeus females preferred the chemicalcues from conspecifics over those of X. cortezi males. However,preference for the chemical cues of conspecifics could not reversethe preference for larger heterospecific males. Only when femaleswere presented with two species-specific cues (vertical barsand chemical cues) did more females spend more time on averagewith the smaller conspecific males. These results support the"backup signal" hypothesis for the evolution of multiple preferences;together, the two species-specific cues increased the accuracywith which females were able to avoid heterospecific males.In addition, the results suggest that in those situations inwhich the traits of conspecifics overlap with traits found inheterospecifics, females can use the assessment of multiplecues to avoid mating with heterospecifics without compromisingtheir preference for the highest-quality conspecific.     

Increased performance of offspring sired by parasitic males in bluegill sunfish

Males of many species are characterized by alternative matingtactics. In bluegill sunfish (Lepomis macrochirus), some malesdelay maturation and become "parentals" while other males matureprecociously and become "cuckolders." Parentals use an overt,territorial mating tactic, defending a nest and courting females.Cuckolders instead use a sneaking tactic to parasitize parentals.It has previously been shown that parentals that are heavilycuckolded provide less care to their young, yet females do notappear to discriminate against cuckolders, and they may actuallyrelease more eggs when a cuckolder is present than when spawningonly with a parental. Here I examined growth rate of fry ofknown paternity through the yolk-sac stage of development usingcomplementary laboratory and field studies to assess a potentialindirect benefit for females that mate with cuckolders. Comparisonof maternal half-siblings sired in vitro shows that cuckolderoffspring grow faster and to a larger size than parental offspringwhile feeding endogenously on their yolk sac. Because both foodresource and maternal genes are equivalent across treatments,these data indicate a genetic difference in growth between thetwo male life histories. In the field, fry from nests that haveproportionately more cuckolder offspring are larger when theyemerge from the nest. This increased size can lead to threefoldhigher survivorship for cuckolder offspring than parental offspringfrom Hydra canadensis predation, a major predator of bluegillfry. These results are discussed in the context of mate choicefor direct and indirect benefits and in the context of the evolutionof alternative mating tactics.     

Male morphological variation and the determinants of body size in two Otiteselline fig wasps

The chalcid wasps (Hymenoptera) that develop in fig tree inflorescences(Ficus: Moraceae) have often been used to study alternativereproductive behaviors. However, recent work suggests that suchbehaviors are more complex than previously thought. We investigatedthis in Otitesella longicauda and O. rotunda. In addition toknown dimorphisms in the two species (each have "religiosa"males that use their mandibles to fight for mates in the fig,and "digitata" males that disperse from the fig to mate), wefound that religiosa males below species-specific body sizeswitch points have relatively larger mandibles and are lesssclerotized than those above. Thus, they are actually trimorphic.We suggest that the religiosa morph variation is linked to fighter/nonfighteralternative mating behaviors, with small (nonfighting) maleshaving relatively larger mandibles because they also use themto pull females out of their galls before mating. Also, we investigatedthe determinants of wasp body size, and whether females (foundresses)adjust their offspring allocation strategies according to expectedoffspring size. We found that wasp size is larger in ovariesnear the center of the fig, and more females and fewer religiosamales are laid in such ovaries than in those further away. Thisprobably indicates that foundresses lay females when they areexpected to be large because their fitness is more body size–dependentthan that of religiosa males. We then discuss the implicationsof our findings for the study of alternative reproductive behaviorsand foundress offspring allocation strategies.     

The effect of age on encounters between male crab spiders

In males that compete aggressively for females, size and agemay determine which males obtain access to these females. Inthe present study, we use the crab spider, Misumena vatia, aspecies with males that do not grow after becoming sexuallymature adults, to test the hypothesis that age affects the successof males competing for access to females. M. vatia is an excellentspecies to test this hypothesis because it is possible to disentangleage from size, characters that typically vary together in thespecies usually tested. We staged encounters between similar-sizedolder and younger adult male M. vatia in the presence of a femaleto determine the role of age in male access to females. Encountersbetween the males occurred during 63.3% of these pairings. Youngermales won significantly more (70.2%) of the encounters thandid older ones, but did not initiate significantly more encountersthan did older ones (62.5%). Although older males won only 29.8%of these encounters, they initiated significantly more (76.5%)of them than predicted by chance. This design also allowed usto test Parker's hypothesis that older individuals should exhibita higher level of aggression than younger ones. However, attacksby younger males were most likely to include extensive bodilycontact, whereas attacks by older males involved significantlyless contact. These results counter the frequent assertion thatolder individuals usually prevail over younger ones in contestsfor access to females, and that older males are more likelyto engage in highly overt aggression than are younger ones.Aging may decrease reproductive opportunities and success ratesof male M. vatia, affecting as many as nearly one-fourth oftheir encounters.     

Bellows, copulations, and sexual selection in bison (Bison bison)

We provide data on the timing and frequency of bellowing episodesand 261 copulations in North American bison (Bison bison) extractedfrom more than 8500 h of observation to examine Darwin's ideathat by using breeding-season vocalizations the male "endeavoursthus to charm or excite the female." Copulatory status affectedvocalization rates; after mating, the frequency of male bellowingdropped to 16.1% of precopulatory rates (p < .0001). Malesbellowed at a higher rate on days when females were in estrus(p < .025) than when they were in anestrus, but females'probability of offspring production in the next year was notcorrelated with bellowing rate. For estrous females, bellowingwas positively correlated with number of attendant males (p< .0001) and inversely related both to the number of daysindividual males had participated in the rut (p < .05) andto the date during the 6-week breeding season (p < .003).Body size also influenced bellowing rate: with other factorsheld constant, small males bellowed more than large males (p< .03). With respect to Darwin's idea that vocalizationsserve as a male display to females, (1) males bellowed neitherbefore nor after copulating when rivals were absent but (2)they bellowed both before and after copulating when rivals werepresent. Overall, these results suggest that bison bellows donot serve as advertisements to females but function as intrasexualdisplays. [Behav Ecol 1991; 2: l-6]     

Greater opportunities for sexual selection in male than in female obligate brood parasitic birds

Females are expected to have evolved to be more discriminatory in mate choice than males as a result of greater reproductive investment into larger gametes (eggs vs. sperm). In turn, males are predicted to be more promiscuous than females, showing both a larger variance in the number of mates and a greater increase in reproductive success with more mates, yielding more intense sexual selection on males vs. females (Bateman's Paradigm). However, sex differences in costly parental care strategies can either reinforce or counteract the initial asymmetry in reproductive investment, which may be one cause for some studies failing to conform with predictions of Bateman's Paradigm. For example, in many bird species with small female‐biased initial investment but extensive biparental care, both sexes should be subject to similar strengths of sexual selection because males and females are similarly restricted in their ability to pursue additional mates. Unlike 99% of avian species, however, obligate brood parasitic birds lack any parental care in either sex, predicting a conformation to Bateman's Paradigm. Here we use microsatellite genotyping to demonstrate that in brood parasitic brown‐headed cowbirds (Molothrus ater), per capita annual reproductive success increases with the number of mates in males, but not in females. Furthermore, also as predicted, the variance of the number of mates and offspring is greater in males than in females. Thus, contrary to previous findings in this species, our results conform to predictions of the Bateman's Paradigm for taxa without parental care.     

Allometry and sexual selection of male weaponry in Wellington tree weta, Hemideina crassidens

Both male and female Wellington tree weta, Hemideina crassidens,use cavities in trees as diurnal shelters. That these galleriesare often limiting in nature offers males the opportunity toincrease their reproductive success by monopolizing galleriesand the females residing in them. Male H. crassidens, can matureat either the 8th, 9th, or 10th instar, whereas females matureat the 10th instar only, and male head (and mandible) size positivelycovaries with ultimate instar number. It has been suggestedthat males fight for control of galleries by using their enlargedmandibles as weapons, and males with larger mandibles controlgalleries with more females. In the present study, I presenta statistical examination of sexual dimorphism, showing thattraits related to head size are on average significantly largerin males, whereas traits related to body size are on averagesignificantly larger in females. I tested three predictionsaddressing the hypothesis that sexual selection is driving megacephalyin male H. crassidens. First, as predicted, traits related tohead size show a positive allometric relationship with bodysize in males but not in females. Second, adapting a novel statisticaltechnique based on maximum likelihood and bootstrapping revealedthat males, but not females, exhibit a multimodal distributionin head and body size traits. This is likely a consequence ofmales maturing at one of three instars, which results in positivecovariance between the ultimate instar number and morphologicaltraits. Third, as predicted, single adult males with largerheads reside in galleries housing larger groups of adult females.     

Patterns of Parental Investment and Sexual Selection in Teleost Fishes: Do They Support Bateman's Principles?

Bateman demonstrated differences in variance for fertility andmating success between the sexes, with males usually havinga greater variance than females. Thus in general, male reproductivesuccess increases with number of mates acquired. These resultshave been referred to as "Bateman's principles" and taken togetherwith other parameters (e.g., relative parental investment) havebeen proposed to estimate a component of sexual selection. Forthis review I examine patterns of parental care and sexual selectionin teleost fishes (substrate brooding and with internal fertilization).I present data for the pumpkinseed sunfish Lepomis gibbosus,in which I estimated cost of paternal care and compared directmeasures of the intensity of selection on possible sexuallyselected traits to measures of sexual selection based on Bateman'sprinciples. Despite high levels of paternal care in substrate brooding fishes,sexual selection tends to act more strongly on males than onfemales, which suggests that maternal investment is higher thanpaternal investment and that parental care does not limit thereproductive rate for males. In pumpkinseed sunfish, selectionfavors parents with high levels of defense that may excludepredators more effectively and, as suggested by Bateman's measures,alternative reproductive strategies may decrease the opportunityfor sexual selection within the parental strategy. In teleostfishes with internal fertilization, patterns of parental investmentand intensity of sexual selection seem to support Bateman'sprinciples, but further studies using these systems and thesemeasures of selection will improve the understanding of factorsaffecting the intensity of sexual selection and its relationto mating systems.     

Tests of the mate-guarding hypothesis for social monogamy: male snapping shrimp prefer to associate with high-value females

Social monogamy without biparental care has evolved in manytaxa, and a number of hypotheses have been developed to explainthis phenomenon. Several authors have suggested the importanceof male mate-guarding behavior in the evolution of social monogamy,although empirical support for this hypothesis is lacking. Inthe caridean shrimp genus Alpheus, social monogamy may resultfrom selection on males for long-term guarding of females becausemating is temporally restricted to a short time after the female'smolt. I used Alpheus angulatus to test two predictions of theextended mate-guarding hypothesis: Males should (1) be physiologicallycapable of predicting the timing of female sexual receptivity,and (2) prefer to associate with (guard) females that are closerto sexual receptivity. Data from a Y-maze experiment testingfor distance chemical communication showed that males of A.angulatus were attracted to water treated by exposure to premoltfemales, repulsed by water treated by exposure to intermoltmales and females, and did not appear to respond in either directionto water treated by exposure to premolt males. In mate choiceexperiments, significantly more males paired with premolt femalesthan with postmolt females. These data suggest that males ofA. angulatus engage in precopulatory mate-guarding behavior.Other factors (population density, sex ratio) may have playeda role in the temporal extension of mate guarding to socialmonogamy.     

Food, vigilance, and sperm: the role of male direct benefits in the evolution of female preference in a polygamous bird

The adaptive significance of female selection of copulationpartners remains unresolved, particularly in polygamous specieswhere males do not provide paternal care. In these species thepossibility that direct benefits other than paternal care mayplay an important role in the evolution of female choice hasreceived little attention. I tested whether direct benefitsare associated with female choice in the polygamous feral fowl,Gallus g. domesticus, where females prefer socially dominantcopulation partners and males do not care for the young butdo provide females with three commodities: food, vigilance,and sperm. I used a combination of empirical and experimentaldata to show that male propensity to offer food and vigilance,but not sperm, was positively associated with male social status,suggesting that the provision of these resources may be costlyand condition dependent in males. Copulation success was correlatedwith male status but not with the number of feedings a femalereceived from a male, indicating that a female preferred dominantpartners that in general provided any female with more food,rather than partners that provided only her with more food,consistent with the idea that females may use male resourceprovisioning as a proximate mechanism to assess male condition.Together, these results indicate that male resources provisioningis (1) tightly linked to male social status, (2) a potentialindicator of male condition and possibly genetic quality, and(3) a potential criterion for females to select dominant partners,thus playing an important role in the evolution of partner choiceeven in polygamous species lacking paternal care.     

Male fruit flies learn to avoid interspecific courtship

Experimental data suggest, and theoretical models typicallyassume, that males of many fruit flies (Drosophila spp) areat least partially indiscriminate while searching for mates,and that it is mostly the females who exert selective mate choice,which can lead to incipient speciation. Evidence on learningby male D. melanogaster in the context of courtship, however,raises the possibility that the initially indiscriminate malesbecome more selective with experience. I tested this possibilityby comparing the courtship behavior of male D. melanogasterexperienced at courting females of the closely related species,D. simulans, and inexperienced males. I found that comparedwith the inexperienced males, the males experienced with courtingD. simulans females showed significantly lower courtship towardfemale D. simulans. Both male treatments, however, showed virtuallyidentical courtship durations with female D. melanogaster. Theseresults indicate that male fruit flies adaptively refine theircourtship behavior with experience and suggest that the malescontribute more to assortative mating and incipient speciationthan is commonly assumed.     

The Red Queen Visits Sage Grouse Leks

Coevolution between parasites and host is a sufficient althoughnot necessary condition for the evolution of secondary sexualcharacteristics. I review evidence supporting the role of parasitesin the maintenance of lek behavior in Sage Grouse (Centrocercusurophasianus). Males bearing avianmalaria (Plasmodium pediocetii)or lice (Lagopoecus gibsoni or Goniodes centrocerci) have significantlylower reproductive success than noninfected males. Malaria-infectedmales attend leks significantly less frequently and lek attendanceis highly correlated with male reproductive success. Inaddition,males with malaria secured copulations later in the breedingseason with hens that wereyounger, in poorer condition, andless successful than mates of malaria-free males. Lice createhematomas on the air sacs of males which females can detectto avoid lousy males. Results of our field studies are reinforcedby experiments; captive males given antibiotics to reduce parasiteloads are chosen more often by females in arena trials. Ourresults lend empirical support for Hamilton and Zuk's (1982)interpretation of the RedQueen's hypothesis, although many unknownsremain in our understanding of the interaction between parasitesand Sage Grouse.     

卷蛾分索赤眼蜂和拟澳洲赤眼蜂对小菜蛾利他素各成分的嗅觉反应

卷蛾分索赤眼蜂Trichogrammatoidea bactrae Nagaraja和拟澳洲赤眼蜂Trichogramma confusum Viggiani是小菜蛾Plutella xylostella (L.)的优势寄生蜂。本研究利用“Y”型管测定了2种赤眼蜂对小菜蛾P. xylostella利他素-卵表和腹部鳞片13种饱和烷烃的嗅觉反应。结果显示: 卷蛾分索赤眼蜂交配雌蜂进入2, 6, 10, 14-四甲基十五烷、正十五烷、正十七烷处理区的百分数分别为80.65%, 68.75%和66.67%, 表明这3种烷烃对卷蛾分索赤眼蜂交配雌蜂有显著的吸引作用, 其他10种饱和烷烃对卷蛾分索赤眼蜂雌蜂无明显作用。拟澳洲赤眼蜂进入2, 6, 10, 14-四甲基十五烷、正三十五烷和正十五烷处理区的数目分别占84.38%, 70%和62.16%, 表明其对拟澳洲赤眼蜂交配雌蜂起着显著的吸引作用, 而另外10种烷烃对拟澳洲赤眼蜂雌蜂无作用。卷蛾分索赤眼蜂和拟澳洲赤眼蜂未交配雄蜂进入13种烷烃处理区和对照区的时间均无显著差异, 表明利他素各组分对2种赤眼蜂未交配雄蜂均无吸引作用。     

Competition for landmark territories among male Polistes canadensis (L.) (Hymenoptera: Vespidae): large-size advantage and alternative mate-acquisition tactics

Alternative male mating tactics of insects at landmarks (leks)have only rarely been investigated. Some males of the paperwasp, Polistes canadensis (L.), were territorial at small treesalong the crests of dry ridges in Santa Rosa National Park,Costa Rica. Territories did not contain nests or resources forwhich females foraged. Contrary to other "hilltopping" species,male P. canadensis competed most intensely for territories insaddles along these ridges rather than at the highest points.Nonterritorial males patrolled small areas of the ridge line,following a path that took them to a number of territories.Many males switched between territoriality and patrolling, suggestingthat both size-related tactics belong to one conditional strategy.Males that were territorial on 2 or more days were larger thanthose that were territorial on only 1 day, and these in turnwere larger than permanent patrollers. Moreover, the mean sizeof territorial males was positively correlated with two measuresof territory attractiveness, suggesting that larger males monopolizepreferred sites. Mean age of territorial males was also relatedto territory attractiveness, but males of intermediate age claimedthe most attractive territories.     

Bidirectional communication system in katydids: the effect on chorus structure

Unlike most acoustic systems evolved for pair formation whereonly males signal, the katydidPhaneroptera nana has a bidirectional communication system where both males and females sing. Despiteextensive study on male chorusing behavior in different communicationsystems, this behavior has rarely been explored in duettingspecies. I examined how this bidirectional communication systemaffects the collective pattern of male signaling.P. nana malesalternate their songs, and in response to synthetic stimulidelay their calls, according to the phase of stimulation. Pairsof synthetic calls (simulating alternating males) presentedto females elicited equal female response, as long as the intercallinterval was 200 ms. Thus, male alternation is imposed by thefemale's responsiveness and may be interpreted as a "jammingavoidance reaction." Further evidence suggests that chorusstructure is not merely constrained by the female sensory temporalresolution, but rather is adaptively related to female choicein this species.     

Nonlocal male mountain white-crowned sparrows have lower paternity and higher parasite loads than males singing local dialect

Bird song often varies geographically, and when this geographicvariation has distinct boundaries, the shared song types arereferred to as song dialects. We investigated the role of songdialect in male mating success in a wild breeding populationof mountain white-crowned sparrows (Zonotrichia leucophrysoriantha). In 2 of 3 years, males singing unusual songs ("nonlocal"males) had lower total fertilization success (measured by microsatellitepaternity analysis) than did males singing the local dialect ("local" males). Similarly, females produced disproportionately more young with local than with nonlocal males. However, dialectwas not a significant predictor of male mating success whencontrolling for other factors that might affect paternity.Instead, the low mating success of nonlocal males was apparentlydue to an interaction between song dialect and parasite load.Nonlocal males were more severely infected by bloodborne Haemoproteusthan were local males, although they did not differ in anyother measured aspect of quality. Immigrant birds may be immunologically disadvantaged, possibly due to a lack of previous experiencewith the local parasite fauna, resulting in low mating success.     

Sexual harassment in live-bearing fishes (Poeciliidae): comparing courting and noncourting species

Sexual harassment by males has been reported from several live-bearingfishes (Poeciliidae) and has been shown to inflict costs onfemales. For example, poeciliid females have reduced feedingopportunities when accompanied by a male because females dedicateattention to avoiding male copulation attempts. Poeciliid speciesdiffer considerably in male mating behavior, such as the presenceor absence of courtship. Courting males display in front ofthe females, but males attempting to sneak-copulate approachfemales from behind, that is, in the blind portion of theirvisual field, and force copulations, which can be viewed asa male persistence trait. We predicted that poeciliid femalesneed to be more vigilant in the presence of noncourting males,and costs of harassment by noncourting males might be stronger.In a comparative approach we examined the costs of male sexualharassment for females as reduced feeding time in 9 speciesof live-bearing fishes, including courting (Poecilia latipinna,Poecilia reticulata, Xiphophorus cortezi, Xiphophorus variatus)and noncourting species (Poecilia mexicana [surface- and cave-dwellingform], Poecilia orri, Gambusia affinis, Gambusia geiseri, Heterandriaformosa). In all species examined except for the cave form ofP. mexicana, focal females spent significantly less time feedingin the presence of a male than when together with another female.The time females spent feeding was found to significantly declinewith increasing male mating activity (sum of all sexual behaviors),but there was no support for the idea that females would spendmore time feeding in the presence of courting males comparedwith noncourting ones.     

Influences of sex, size, and symmetry on ejaculate expenditure in a moth

Although sperm fundamentally function to fertilize eggs, forcesarising from both sexes select for optimal ejaculate composition.Sperm competition is one recognized agent in the evolution ofsperm and ejaculate structure. Few studies, however, have examinedhow female factors influence ejaculate structure, despite somebehavioral evidence for male mate choice. Male Plodia interpunctella(Lepidoptera, Pyralidae) accrue all resources for reproductionas larvae. Adults emerge with a limited sperm complement andare therefore under intense selection to optimize gamete allocation.I detected no effect of male body weight on ejaculate size.However, female reproductive potential (ovary masses) was dictatedby body weight In addition, heavier females had greater spermathecalvolumes, but there was no such relationship with bursal size.Finally, heavier females showed a higher mating frequency. Ifound that mating males were sensitive to female size and producedlarger ejaculates when mating with heavier females. Males mayejaculate more sperm into larger females either because it paysthem to "spend" more reproductive resources on matings thatprovide greater reproductive potential, or because heavier (longerlived and more attractive) females mate more frequently andhave larger spermathecal volumes. Alternatively, females maycontrol spermatophore formation and "accept" an appropriateejaculate to maximize fertility. Males may therefore be alsoselected to ejaculate more sperm into larger females to counteractgreater risks of sperm competition associated with heavier females.There was no association between male or female femur asymmetryand ejaculate size. P.interpunctella may be selected to exercisemodulation of ejaculate size because males invest paternally,sperm for the single reproductive episode are limited, and femalefecundity and mating pattern vary between individuals and areassociated with body weight. More obvious variability in malereproductive behavior and choice may therefore be paralleledat the cryptic gametic level by plasticity in ejaculate allocation.     

The role of behavioral dominance in structuring patterns of habitat occupancy in a migrant bird during the nonbreeding season

Several species of territorial migratory birds exhibit sexualhabitat segregation on their wintering grounds, with some habitatscontaining mostly males and others mostly females. The objectiveof this study was to determine if in the American redstart(Setophaga ruticilla) in Jamaica habitat segregation is dueto social mechanisms or due to sex-specific habitat specialization.I used habitat-specific patterns of arrival by young males and females, observations of territorial displacements, removalexperiments, and simulations of territorial intrusions to differentiatebetween these two mechanisms. Redstarts were studied in twohabitat types, a male-biased mangrove forest and a female-biasedscrub habitat. In autumn, male and female hatch-year redstartsinitially settled in equal numbers in each habitat, and segregationof the sexes occurred gradually and mostly later in the arrival period. This shift corresponded with an increase in densityof older birds and an increase in territorial displacements.Removal experiments showed that vacancies in male-biased habitatwere filled more rapidly and with greater frequency than thosein female-biased habitat and that vacated male territoriesin mangrove were replaced more often by females than by males. Simulations of territorial intrusions and analyses of body sizeindicated that levels of aggression and body size of both malesand females were greater in mangrove habitat, suggesting thatthese factors may be important in determining the outcomesof dominance interactions. I conclude that patterns of sexualhabitat segregation in redstarts are structured by the dominance behavior of older and more dominant individuals, and these aremostly males.