Morphological and sexual traits in Atlas and Iberian Pied Flycatchers Ficedula hypoleuca speculigera and F. h. iberiae: a comparison

Capsule: There are significant biometric differences between Pied Flycatchers from Iberian and north African populations which are consistent with proposals to classify the two forms into separate species.

Aims: To determine the similarities and differences in the main biometrical and plumage sex traits between populations of the Iberian Pied Flycatcher Ficedula hypoleuca iberiae and the Atlas Flycatcher Ficedula hypoleuca speculigera.

Methods: Biometric and plumage traits of 193 breeding individuals of Iberian Pied Flycatchers and 43 Atlas Flycatchers were measured in 2014 with standardized protocols.

Results: Both sexes of Atlas Flycatchers were larger than Iberian Pied Flycatchers in skeletal (tarsus) and wing size and also differed in bill morphology, which was wider but shallower in speculigera than iberiae, with females (but not males) having shorter bills than iberiae females. Males differed in mantle colour and forehead patch size, with speculigera males being darker and displaying larger forehead patches than iberiae males. As in populations of iberiae, some speculigera females also expressed a white forehead patch.

Conclusion: We demonstrate significant phenotypic differences between Iberian Pied Flycatchers and Atlas Flycatchers with respect to size and traits of ecological and evolutionary relevance, supporting the recently proposed scenarios on their independent evolution.     

Female ornaments in the Pied Flycatcher Ficedula hypoleuca: associations with age, health and reproductive success

Female ornamentation has received little attention in studies of sexual selection. Traditionally, female ornaments have been explained as a genetically correlated response to selection in males. However, recent findings suggest that female ornaments may be adaptive. Southern populations of Pied Flycatchers Ficedula hypoleuca are suited for studies of female ornamentation because, in addition to the white wing patch, some females also express the white forehead patch characteristic of males. We thus addressed the associations of these two ornaments with female age and with some health and breeding parameters in a Spanish population of Pied Flycatchers. Female ornament expression was not associated with haemoparasite prevalences, clutch size or parental provisioning effort. However, females expressing the white forehead patch raised more fledglings, and females with larger wing patches bred earlier, had higher number of hatchlings and showed increased levels of total serum immunoglobulins. Thus, these two unrelated epigamic ornaments may indicate some aspects of female quality. Further experimental studies could test the possibility that these plumage traits might function as signals to the males or might be used during female–female aggressive encounters in competition for nest-sites and mates.     

POPULATION DIVERGENCE IN SEXUAL ORNAMENTS: THE WHITE FOREHEAD PATCH OF NORWEGIAN PIED FLYCATCHERS IS SMALL AND UNSEXY

Models of sexual selection suggest that populations may easily diverge in male secondary sexual characters. Studies of a Spanish population of the pied flycatcher, Ficedula hypoleuca, and a Swedish population of the closely related collared flycatcher, F. albicollis, have indicated that the white forehead patch of males is a sexually selected trait. We studied the white forehead patch of male pied flycatchers (n = 487) in a Norwegian population over seven years. Males with large forehead patches were in general more brightly colored, but patch height was not correlated to body mass, body size, or parasite loads. Conditions during the nestling period did not seem to influence patch height as an adult. Patch height increased slightly from the first to the second year as adults, but then remained relatively constant at higher ages. Patch height was not related to survival. Year-to-year changes showed that males who increased in patch height also increased in body mass, suggesting that expression of the forehead patch may be partly condition dependent. However, changes in body mass explained only a small proportion of the variance in patch height between males. Thus, patch height would not be a good indicator of male quality. Furthermore, patch size was also not related to male ability to feed nestlings, indicating that females would not obtain direct benefits by choosing males with large patches. However, patch height could be a Fisher trait, but this requires heritability and there was no significant father-son resemblance in patch height. Comparisons of the males visited by each female during the mate sampling period indicated that chosen males did not have larger forehead patches than rejected males. Experimental manipulation of patch height did not affect male mating success. These results indicate that females do not use patch size as a mate choice cue. Finally, patch height did not predict the outcome of male contests for nestboxes, suggesting that the forehead patch is not an intrasexually selected cue of status. Norwegian pied flycatchers have smaller forehead patches than both Spanish pied flycatchers and Swedish collared flycatchers. We suggest that this pattern may be explained by the lack of sexual selection on the forehead patch in the Norwegian population as compared to the other populations, where the patch is apparently sexually selected. We discuss possible reasons for these population divergences, such as female choice on an alternative secondary sexual character (general plumage color) and speciation among Ficedula flycatchers.     

Mutual ornamentation and the parental behaviour of male and female Collared Flycatchers Ficedula albicollis during incubation

One of the benefits of mate choice based on sexually selected traits is the greater investment of more ornamented individuals in parental care. The choosy individual can also adjust its parental investment to the sexual signals of its partner. Incubation is an important stage of avian reproduction, but the relationship between behaviour during incubation and mutual ornamentation is unclear. Studying a population of Collared Flycatchers Ficedula albicollis, we monitored the behaviour of both sexes during incubation in relation to their own and their partner's plumage traits, including plumage‐level reflectance attributes and white patch sizes. There was a marginally positive relationship between male feeding rate during incubation and female incubation rate. Female but not male behavioural traits were associated with the laying date of the first egg and clutch size. The behaviour of the two sexes jointly determined the relative hatching speed of clutches and the hatching success of eggs. Females with larger white wing patches spent less time incubating eggs and left the nestbox more frequently. Males with larger white wing patches fed females less frequently, whereas males with brighter white plumage areas visited the nestbox more regularly without feeding. Females tended to leave the nest less often when mated to males with larger wing patches, and females spent less time incubating when males had more UV chromatic plumage. The behaviour of both partners during incubation therefore predicted hatching patterns and was correlated with their own and sometimes with their partner's plumage ornamentation. These results call for further studies of mutual ornamentation and reproductive effort during incubation.     

Ontogenetic variation in the plumage colour of female European Pied Flycatchers Ficedula hypoleuca

Although variation in the dorsal plumage colour of male European Pied Flycatchers Ficedula hypoleuca has received a great deal of attention, females of the species have been usually considered to be nearly uniformly monochromatic brown. Using reflectance spectrophotometry, we explore the age‐dependent variation of plumage colour in females. We disentangle the within‐ and between‐individual effects of this pattern and show a within‐individual darkening of the mantle colour with age, whereas differences between individuals in structural colour expression may underlie the trend for a more reflective white in the females' breast plumage with advancing age. The darkening of the dorsal plumage as females age reflects the most common pattern of age‐related variation in males in most European populations of the species.     

Females Paired with More Attractive Males Show Reduced Oxidative Damage: Possible Direct Benefits of Mate Choice in Pied Flycatchers

Direct benefits of female mate choice may concern female fertility and fecundity but also physiological status. In birds with biparental care, males may contribute to improve the condition and health of their pair‐mates through help in constructing nests, incubation or incubation feeding and nestling provisioning. They may also reduce harassment of females by non‐pair males. A consequence of these male activities could be expressed in terms of oxidative damage, which may depend on metabolic effort and social stress. Here, we have related male contribution to parental and territorial duties to female oxidative status in the pied flycatcher Ficedula hypoleuca, a species where preferred males present darker dorsal plumage and, in Iberian populations, a large white forehead patch. Darker males were paired with females with high incubation attendance and reduced nestling provisioning rates, which may lead to reduced female exertion. These males owned nest boxes at which there were fewer visits by non‐pair males. Although females paired with dark mates worked less hard, they were able to raise more fledglings. Female oxidative damage measured as malondialdehyde (MDA) level in plasma declined with increasing incubation attendance and male incubation feeding. Moreover, levels of MDA in females declined with both darkness of male dorsal plumage and male forehead patch size when controlling for female forehead patch size and male age. The effect of male plumage darkness was especially strong. Females paired with middle‐aged males (2–3 yr) showed reduced levels of MDA compared with those paired with 1‐yr‐old and more than 3‐yr‐old males. Male age could not explain the effects of male attractiveness. Females paired with attractive males were more successful in reproduction while suffering reduced oxidative damage, possibly mediated by help during incubation and nestling rearing from their pair‐mates. Although correlative, the evidence suggests direct benefits of females paired with more attractive males.     

Some male Pied Flycatchers Ficedula hypoleuca in Iberia become collared with age

The development of a collar in Pied Flycatchers Ficedula hypoleuca in Spain is described and its ontogenetic and genetic variation and phenotypical correlates are analysed. Collared males were older than males having traces of collar or lacking one. Also, males showing a collar or trace of a collar had larger white forehead patches than those lacking a collar. Intrapopulation variation in both collar expression and white patch size, which might be genetically determined but phenotypically decoupled in temporal expression, resembles between-species variation among the black and white European flycatchers.     

Bacterial degradability of white patches on primary feathers is associated with breeding date and parental effort in a migratory bird

We compared the in vitro bacterial degradability of the white patch and melanized area of primary feathers of breeding male and female Pied Flycatchers Ficedula hypo‐leuca and related this variation to laying date, brood size and brood mass. Bacterial degradability of male and female white feather patches, but not of melanized areas, was positively correlated with laying date. Male Pied Flycatchers showed a positive correlation between bacterial degradability of the white patch, though not of the melanized patch, and brood size and brood mass. Feather degradability appears to be negatively related to individual quality and positively related to reproductive effort.     

Female wing plumage reflects reproductive success in Common Goldeneye Bucephala clangula

Recent studies on the function of female plumage characteristics have yielded ambiguous results. Some studies have found an association between different physiological, ecological or behavioural traits and female plumage, while others have found no association and interpret female plumage as neutral in function. We observed a high variance among females in both wing plumage and breeding success in female Common Goldeneyes Bucephala clangula , a sexually plumage-dimorphic diving duck. We studied the association between female wing plumage and hatching date. Principal component analysis of four wing patch area measurements derived a single factor describing wing plumage. Wing plumage was strongly associated with hatching date, which is the most important determinant of goldeneye recruit production; irrespective of age, females with more white in the wing bred earlier than individuals with more black in the wing. We propose that the wing pattern in Common Goldeneye females reflects individual quality.     

Distribution and reproductive success of the Pied Flycatcher Ficedula hypoleuca in relation to forest patch size and vegetation characteristics; the effect of scale

We studied habitat choice, distribution and reproductive success in the Pied Flycatcher Ficedula hypoleuca in relation to the spatial structure of a fragmented forest area. Two hierarchical levels of forest habitat structure were used: (1) forest patch size (macrohabitat) and (2) vegetative structure within forest patches (microhabitat). In spring, both males and females settled preferentially in large and medium-sized forest stands (>1 ha) where breeding density was also higher than in small stands (<1 ha). Stands <5 ha were occupied later, and the proportion of unpaired males was higher there than in large stands (>5 ha). The known age distributions of breeding birds and breeding success were independent of forest patch size. Nest predation rate was not associated with stand size or nest distance from the forest edge. The preference of breeding birds for large forest patches was presumably related to the higher amount of resources (nest sites, mates, food) a large patch can offer for reproduction compared with a small patch. At the microhabitat level, territories of old males were characterized by relatively more deciduous trees that contained more invertebrate food than coniferous tree-dominated territories of yearling males. The reproductive success of old males, as measured by the number of fledged young per male, was higher than that of yearling males. This suggests that the larger body size and blacker plumage of old males possibly contributed to male dominance and that old males excluded younger males from preferred habitats through territorial behaviour. Our results suggest that habitat choice of the Pied Flycatcher was affected by both micro- and macrohabitat. On the basis of settlement pattern, density and reproductive success, the distribution of Pied Flycatchers across forest stands of different sizes followed the ideal-free distribution model, whereas at the microhabitat level, age-related unequal distribution of males followed the ideal-despotic model of Fretwell and Lucas.     

Qualitative population divergence in proximate determination of a sexually selected trait in the collared flycatcher

We examined proximate determination of sexually selected forehead patch size in a Central‐European population of Ficedula albicollis, the collared flycatcher, using a 9‐year database, and compared our results with those obtained in other populations of the same and the sister species. Between‐individual variation of forehead patch size was large, its repeatability larger than, and heritability similar to the Swedish population. Unlike in the other populations, the trait proved unaffected by body condition, and only very slightly influenced by age. There was no relationship between forehead patch size and breeding lifespan, and a marginal negative association with survivorship in adult males. Our results suggest that additive genetic variance of the trait in this population is large, but genes act independently of body condition, and there is no viability indicator value of the trait. This is the first report of a qualitative intraspecific difference in proximate determination of a sexually selected trait.     

Variation in the extra-pair mating systems of Acadian Flycatchers and Wood Thrushes in forest fragments in southern Ontario

ABSTRACT.   The application of molecular tools to studies of avian mating systems has revealed that most songbird species engage in extra-pair matings. However, little is known about the possible effects of habitat fragmentation on extra-pair mating systems. During the breeding seasons of 2002 and 2003, we quantified the frequency of extra-pair matings in Acadian Flycatchers ( Empidonax virescens ) and Wood Thrushes ( Hylocichla mustelina ) nesting in forest fragments in southern Ontario. Acadian Flycatchers are at the limit of their northern range in southern Ontario and occurred at low densities (0.005–0.015 males/ha). Across forest fragments, 14% of young Acadian Flycatchers were the result of extra-pair fertilizations. In contrast, Wood Thrushes were common in forest fragments, with breeding densities ranging from 0.37 to 1 males/ha. Extra-pair mating was common among Wood Thrushes, with 40% of young the result of extra-pair matings. Compared to populations studied in less fragmented habitats in Pennsylvania, rates of extra-pair paternity in Ontario were lower for Acadian Flycatchers and higher for Wood Thrushes. Our results demonstrate that rates of extra-pair mating can vary across landscapes. However, the extra-pair mating systems of Acadian Flycatchers and Wood Thrushes appear to respond differently to fragmentation. We suggest that low breeding densities on fragments may be mediating the low rates of extra-pair mating observed in Acadian Flycatchers in southern Ontario, whereas changes to the behavioral tactics of male and female Wood Thrushes in southern Ontario may explain the high levels of extra-pair mating.     

Arrival date and territorial behavior are associated with corticosterone metabolite levels in a migratory bird

Glucocorticoids promote the mobilization of energy stores and they may facilitate the expression of energetically expensive functions. Early arrival on the breeding grounds in migratory species and territorial competition are energetically demanding activities that may be supported by elevated baseline glucocorticoid levels. Here, we evaluated the associations between the baseline levels of excreted corticosterone (CORT) metabolites of male Pied Flycatchers (Ficedula hypoleuca) just after arriving on their breeding area and timing of arrival, considering ornamental traits indicative of social status, like forehead patch size and black plumage coloration, as well as heat shock protein levels (HSP60). We observed a positive association of CORT metabolites with HSP60 levels, which are synthesized under several environmental challenges affecting cell homeostasis. Our data showed a negative association between arrival date and CORT metabolite levels, possibly as a result of the higher energetic demands imposed by the hard environmental conditions experienced at the time of an early arrival after migration. We observed a negative relationship of forehead patch dimensions and CORT metabolite levels, suggesting that dominance is associated with low baseline CORT metabolites. Also, males that expressed a higher degree of territorial behaviour when exposed to a playback song of a conspecific at their nest-box showed higher CORT metabolites upon arrival than males that expressed a lower degree of territorial behavior. This may indicate that elevated baseline CORT metabolite levels may facilitate an intense territorial competition in males. Thus, male–male competition may be a factor affecting observed baseline glucocorticoid levels in migratory birds.     

Feather mass and winter moult extent are heritable but not associated with fitness-related traits in a long-distance migratory bird

In birds, the allocation of resources to plumage production may have important fitness consequences. However, we have only a limited understanding of how plumage traits respond to natural selection, making it difficult to predict how variation in plumage traits may contribute to the adaptation of birds to environmental change. In this study, we collected plumage-related data in a pedigreed population of a long-distance migratory bird (the Pied Flycatcher Ficedula hypoleuca) to estimate the heritability of two plumage traits: feather mass (as a proxy of feather quality) and the extent of winter moult. We further explored whether these plumage features were associated with some fitness-related traits. Variation in plumage characteristics could be explained by differences in sex, age and year, which indicates a high degree of plasticity in these traits. After controlling for these effects, however, feather mass and winter moult extent were highly repeatable (r = 0.58–0.82) and heritable (h² = 0.59–0.65), suggesting that additive genetic variation accounts for a significant proportion of the residual phenotypic variation of plumage traits in this population. Although the studied characteristics showed evolutionary potential, we did not find any relationship between plumage features and fitness-related traits like spring arrival date, egg-laying date, mating success or mating-time. We conclude that current selection on feather mass and moult extent, if existing, is weak, and that these moult-related traits are currently of minor importance for the adaptation of our study population to global warming.     

Winter body condition in relation to age,sex and plumage ornamentation in a migratory songbird

Winter body condition may play important roles in the life history of migratory birds, but it is difficult to estimate. We used the growth rate of winter‐grown tail feathers of Collared Flycatchers Ficedula albicollis as an indicator of winter body condition, comparing this trait between age classes and sexes and relating it to plumage ornamentation (forehead and wing patch sizes). Adults and males were in better nutritional condition during winter, as indicated by their faster tail feather growth rates, than were yearlings and females, respectively, which could indicate differences in individual quality and foraging ability with age, or age‐ and sex‐related winter habitat segregation. However, feather growth rate was related neither to the size of the winter‐grown forehead patch nor to the size of the summer‐grown wing patch, suggesting weak condition‐dependence for the winter‐grown ornament and complex life‐history consequences for the summer‐grown ornament.     

Forehead Patch Size Predicts the Outcome of Male–Male Competition in the Pied Flycatcher

Males of many animal species express ornaments that affect their reproduction opportunities through male–male competition or female mate choice. Such ornaments can, for example, inform conspecifics about the fighting ability, condition or territory ownership of the bearer. Pied flycatcher (Ficedula hypoleuca) males have a conspicuous white forehead patch that varies greatly in size. We examined whether the white forehead patch is an intrasexually selected trait in a Finnish population. We artificially manipulated forehead patch size to represent two naturally occurring extremes and competed males against each other in the presence of a female. Males with a large forehead patch were more aggressive than males with a small patch, whereas the original patch size of the male had no influence on aggression. Neither manipulated nor original patch size influenced resource dominance (over female or nest box). These results indicate that forehead patch signals fighting ability of the bearer in the pied flycatcher. The next step is to find out what kind of costs may maintain the honesty of this signal.     

Structural and functional aspects of variation of the breeding plumage ornamentation in the male Pied Flycatcher Ficedula hypoleuca (Aves: passeriformes)

Inter- and intraindividual variation of the breeding plumage ornamentation in male Pied Flycatcher Ficedula hypoleuca from the Moscow province population (55 degrees 44' N 36 degrees 51' E) was studied using long-term data (1996-2005). Eumelanin prevailing colour type (CT) scored according to the seven-step Dorst scale (Dorst, 1936), age, and reproductive status during the current breeding season were analyzed as potential sources of variation of the white ornamentation on the forehead, the wings, and the tail in males. Male CT strongly varied, from almost black to cryptic brownish (2-7, average 4.4, N = 1403). On average CT became I1degree darker with age and tended to be stable after the age of two years. Initial and final CT strongly correlated (r = 0.76). Wing ornamentation and forehead patch (FP) were associated with both initial and final CT, whereas correlation between tail ornamentation and CT was observed only in aged males. Ornamentation was most variable in males with cryptic (pale) CT. Such males had, on average, less intense forehead and wing ornamentation than conspicuous males, compensating this difference by having more intense ornamentation next year. These data suggest the weakening of morphogenetic relations between prevailing colour and ornamentation in males with cryptic phenotype. The return rate (rate of conspicuous males returning to their previous nesting territory) was not related to the success of their previous breeding attempts. Among pale males, the return rate was higher in breeders than in non-breeders. The relation between FP shape and reproductive status was pronounced only in pale males. Among pale males, previous breeders and non-breeders displayed no difference in the degree of prevailing colour darkening next year. In conspicuous males, previous breeding led to the weakening of dorsal eumelanin pigmentation of the new plumage, which suggests the existence of tradeoffs between reproductive efforts and the development of rich eumelanin coloration. Among pale males, previous breeders displayed a higher rate of FP widening next year than previous non-breeders. Diffrerent patterns of relations between male ornamentation and reproductive experience suggest that the females can use plural clues to evaluate the quality of their potential mates.     

Evolutionary trade‐off between naturally‐ and sexually‐selected melanin‐based colour traits in worldwide barn owls and allies

Natural selection typically constrains the evolution of sexually‐selected characters. The evolution of naturally‐ and sexually‐selected traits can be intertwined if they share part of their genetic machinery or if sex traits impair foraging success or increase the risk of depredation. The present study investigated phenotypic correlations between naturally‐ and sexually‐selected plumage traits in the Tytonidae (barn owls, grass owls, and masked owls). Phenotypic correlations indicate the extent to which selection on one trait will indirectly influence the evolution of another trait. In this group of birds, the ventral body side varies from white to dark reddish, a naturally‐selected pheomelanin‐based colour trait with important roles in predator–prey interactions. Owls also exhibit eumelanin‐based black spots, for which number and size signal different aspects of individual quality and are used in mate choice. These three plumage traits are strongly heritable and sexually dimorphic, with females being on average darker reddish and more spotted than males. Phenotypic correlations were measured between these three plumage traits in 3958 free‐living barn owls in Switzerland and 10 670 skin specimens from 34 Tyto taxa preserved in museums. Across Tyto taxa, the sexually‐selected plumage spottiness was positively correlated with the naturally‐selected reddish coloration, with redder birds being more heavily spotted. This suggests that they are genetically constrained or that natural and sexual selection are not antagonistically exerted on plumage traits. In a large sample of Swiss nestlings and within 34 Tyto taxa, the three plumage traits were positively correlated. The production of melanin pigments for one plumage trait is therefore not traded off against the production of melanin pigments for another plumage trait. Only in the most heavily‐spotted Tyto taxa do larger‐spotted individuals display fewer spots. This indicates that, at some threshold value, the evolution of many spots constrains the evolution of large spots. These analyses raise the possibility that different combinations of melanin‐based plumage traits may not be selectively equivalent.     

Geographic variation in sexual dimorphism in the barn owl Tyto alba: a role for direct selection or genetic correlation?

Geographic variation in sexually selected traits is commonly attributed to geographic variation in the net benefit accrued from bearing such traits. Although natural and sexual selection are potentially important in shaping geographic variation, genetic constraints may also play a role. Although a genetic correlation between two traits may itself be the outcome of natural or sexual selection, it may indirectly reinforce the establishment and maintenance of cline variation with respect to one particular trait when across the cline different values of other traits are selected. Using the barn owl Tyto alba, a species in which the plumage of females is more reddish‐brown and more marked with black spots than that of males, I report results that are consistent with the hypothesis that both direct selection and genetic constraints may help establish and maintain cline variation in sexual dichromatism. In this species, inter‐individual variation in plumage coloration and spottiness has a genetic basis, and these traits are not sensitive to the environment. Data, based on the measurement of skin specimens, is consistent with the hypothesis that the stronger European cline variation in male spottiness than in female spottiness depends on the combined effects of (1) the similar cline variation in male and female plumage coloration and (2) the more intense phenotypic correlation between plumage coloration and spottiness in males (darker birds are more heavily spotted in the two sexes, but especially males) which is a general feature among the globally distributed barn owls. In northern Europe, male and female T. a. guttata are reddish‐brown and heavily spotted, and in southern Europe male and female T. a. alba are white, but only females display many spots. Here, I discuss the relative importance of direct selection, genetic correlation and the post‐ice age invasion of Europe by T. alba, in generating sex‐specific cline variation in plumage spottiness and non‐sex‐specific cline variation in plumage coloration.     

Correlational selection leads to genetic integration of body size and an attractive plumage trait in dark-eyed juncos

When a trait's effect on fitness depends on its interaction with other traits, the resultant selection is correlational and may lead to the integration of functionally related traits. In relation to sexual selection, when an ornamental trait interacts with phenotypic quality to determine mating success, correlational sexual selection should generate genetic correlations between the ornament and quality, leading to the evolution of honest signals. Despite its potential importance in the evolution of signal honesty, correlational sexual selection has rarely been measured in natural populations. In the dark-eyed junco (Junco hyemalis), males with experimentally elevated values of a plumage trait (whiteness in the tail or "tail white") are more attractive to females and dominant in aggressive encounters over resources. We used restricted maximum-likelihood analysis of a long-term dataset to measure the heritability of tail white and two components of body size (wing length and tail length), as well as genetic correlations between pairs of these traits. We then used multiple regression to assess directional, quadratic, and correlational selection as they acted on tail white and body size via four components of lifetime fitness (juvenile and adult survival, mating success, and fecundity). We found a positive genetic correlation between tail white and body size (as measured by wing length), which indicates past correlational selection. Correlational selection, which was largely due to sexual selection on males, was also found to be currently acting on the same pair of traits. Larger males with whiter tails sired young with more females, most likely due to a combination of female choice, which favors males with whiter tails, and male-male competition, which favors both tail white and larger body size. To our knowledge, this is the first study to show both genetic correlations between sexually selected traits and currently acting correlational sexual selection, and we suggest that correlational sexual selection frequently may be an important mechanism for maintaining the honesty of sexual signals.