Ornaments are equally informative in males and females: a bivariate meta-analysis in birds

Female ornaments are often reduced, male-like traits. Although these were long perceived as nonadaptive, it is now broadly accepted that female ornaments can be functional. However, it is unclear whether this is as common in females as it is in males, and whether ornaments fulfil similar signalling roles. To test this, we conduct a systematic review and apply a phylogenetically controlled bivariate meta-analysis to a large dataset of ornaments in mutually ornamented birds. As expected, female ornament expression tends to be reduced compared to males. However, ornaments are equally strongly associated with indicators of body condition and aspects of reproductive success in both sexes, regardless of the degree of sexual dimorphism. Thus, ornaments in birds provide similar information in both sexes: more ornamented individuals are in better condition and achieve higher reproductive success. Although limited by their correlational nature, these outcomes imply that female ornaments could widely function in a similar manner as male ornaments.

Static allometry suggests female ornaments in the long-tailed dance fly (Rhamphomyia longicauda) are not deceptive

Despite their prevalence in nature, the evolution of sex-specific female ornaments is still not well understood. Although in some cases (often carotenoid-based ornaments) they appear to honestly signal quality, such as fecundity, it has been suggested that some female ornaments have evolved to deceptively to obtain matings. We address these two hypotheses in the long-tailed dance fly ( Rhamphomyia longicauda ), where females possess two sex-specific ornaments: pinnate scales on the hind femur and tibia and abdominal sacs that are inflated in female-biased display swarms. Although several studies have suggested that female ornaments in this species are deceptive, evidence is mixed and requires further investigation. Here, we use static allometry (with body size as a proxy for condition) of both ornamental and non-ornamental traits in females (and homologous non-ornamental traits in males) in order to determine whether they are honest or deceptive signals of quality. Most male traits scaled isometrically with body size, however male leg hairs showed positive static allometry, probably because they are involved in nuptial-prey capture or in grasping mates. Ornamental traits in females (abdomen area and tibia scale length) showed significant positive allometry and had steep slopes relative to non-ornamental traits. As larger females invest more in ornamentation relative to smaller females, this suggests that these traits are likely honest, condition-dependent signals of quality. We note that honesty and deception are not mutually exclusive hypotheses. Individuals may vary in their signalling strategy, resulting in, for example, deception from some low condition individuals but honesty overall. Although our finding of positive allometry makes it unlikely this occurs in long tailed dance flies, simultaneous honesty and deception should be considered in future studies of female ornamentation.

Colourful traits in female birds relate to individual condition, reproductive performance and male-mate preferences: a meta-analytic approach

Colourful traits in females are suggested to have evolved and be maintained by sexual selection. Although several studies have evaluated this idea, support is still equivocal. Evidence has been compiled in reviews, and a handful of quantitative syntheses has explored cumulative support for the link between condition and specific colour traits in males and females. However, understanding the potential function of females' colourful traits in sexual communication has not been the primary focus of any of those previous studies. Here, using a meta-analytic approach, we find that evidence from empirical studies in birds supports the idea that colourful female ornaments are positively associated with residual mass and immune response, clutch size and male-mate preferences. Hence, colourful traits in female birds likely evolved and are maintained by sexual selection as condition-dependent signals.

Ornaments in Females

In this chapter I want to explore the role of ornamental traits in females. They pose a bit of a conundrum, as they are not really predicted to exist—at least until recently. From a simple sexual selection point of view, female ornaments should be selected against by males because inconspicuous females suffer less predation and are more likely to care for their offspring successfully. Yet, countless species show ornaments in females. Are they adaptations of some kind or just the side effect of a genetic correlation? And what information do female ornaments convey to males?

Male Choice, Female Competition, and Female Ornaments in Sexual Selection

When Darwin first proposed sexual selection theory he suggested two mechanisms: competition among males and choice by females. There is no doubt that these mechanisms are immensely important, but their mirror images have been largely underappreciated so far. In fact, males choose as well and females compete. Males choose based on female quality, often selecting mating partners that are more fecund. But male choice is also associated with changes in the sex ratio of a population and males can be choosy when they are rare. Furthermore, males sometimes invest heavily into reproduction and that too can be associated with male choice. That females compete with another, although less often with open aggression, is another understudied phenomenon. Finally, we now know that females are often ornamented, but are these ornaments under sexual selection by males? This book tries to review what we know and point to what we don’t know while pointing out the connections between male mate choice and female competition for a more complete view of sexual selection.

Does male mate choice select for female colouration in a promiscuous primate species?

The traditional view of sex roles and sexual selection emphasises the evolution of male ornaments as a result of female mate choice and male-male competition. Female ornaments are now receiving more attention, although their roles in mating decision are still less well understood, especially considering cases in which colourful ornaments are expressed by both sexes. In this study, we analysed whether female skin colouration (luminance and redness of the face and hindquarters) influenced male mate choice and sexual behaviours in relation to intra-cycle (cycle phase), inter-cycle (number of consecutive cycles, conceptive nature of the cycle), and inter-individual (age, social rank, weight, and parity) variation in a captive population of Japanese macaques (Macaca fuscata). Males did not preferentially choose darker/redder females. Moreover, males did not appear to use female skin colouration to apportion their mating efforts on the most fertile period of the menstrual cycle or during cycles that lead to conception, or to discriminate between females. To our knowledge, our study is among the few to report a lack of male choice for female colouration in a species where both sexes potentially display ornamentation. While female colouration appeared to contain information about intra-cycle, inter-cycle, and inter-individual variation in fecundity, this study further demonstrates that this trait may not have been sexually selected and that males mated regardless of such variation across females. This study adds to the growing research on the role and evolution of female colouration in the context of sexual signalling and mate attraction.

Sex-specific relationships between urbanization, parasitism, and plumage coloration in house finches

Historically, studies of condition-dependent signals in animals have been male-centric, but recent work suggests that female ornaments can also communicate individual quality (e.g., disease state, fecundity). There also has been a surge of interest in how urbanization alters signaling traits, but we know little about if and how cities affect signal expression in female animals. We measured carotenoid-based plumage coloration and coccidian (Isospora spp.) parasite burden in desert and city populations of house finches Haemorhous mexicanus to examine links between urbanization, health state, and feather pigmentation in males and females. In earlier work, we showed that male house finches are less colorful and more parasitized in the city, and we again detected such patterns in this study for males; however, urban females were less colorful, but not more parasitized, than rural females. Moreover, contrary to rural populations, we found that urban birds (regardless of sex) with larger patches of carotenoid coloration were also more heavily infected with coccidia. These results show that urban environments can disrupt condition-dependent color expression and highlight the need for more studies on how cities affect disease and signaling traits in both male and female animals.

Lunate pendants from the Troitsky Excavation (chronology)

In the chronological distribution of the lunate objects found at the Troitsky (32). Excavation, the first period of their use (10th — first half of the 11th century) is well traceable and substantiated through Nerevsky finds. The chronological lacuna of the second half of the 11th century suggests, firstly, the sacral significance of lunate pendants as heathen amulets in the earliest period and, secondly, the possible loss of their sacral meaning by the early 12th century. Perhaps, since the 12th century, lunate pendants became ordinary female ornaments having lost their sacral function. As it seems, already as early as in the late 12th — beginning of the 13th century, they were possibly considered by the urban residents as Christian amulets and were connected with the cult of the Mother of God.