The status signalling hypothesis aims to explain within-species variation in ornamentation by suggesting that some ornaments signal dominance status. Here, we use multilevel meta-analytic models to challenge the textbook example of this hypothesis, the black bib of male house sparrows (Passer domesticus). We conducted a systematic review, and obtained primary data from published and unpublished studies to test whether dominance rank is positively associated with bib size across studies. Contrary to previous studies, the overall effect size (i.e. meta-analytic mean) was small and uncertain. Furthermore, we found several biases in the literature that further question the support available for the status signalling hypothesis. We discuss several explanations including pleiotropic, population- and context-dependent effects. Our findings call for reconsidering this established textbook example in evolutionary and behavioural ecology, and should stimulate renewed interest in understanding within-species variation in ornamental traits.

Researchers have investigated animals' causal knowledge with a task requiring subjects to use a tool to bring a reward within reach whilst avoiding a trap. Previous studies have suggested limitations in the ability of several species to avoid traps in tubes or tables. However, certain features may have inflated task difficulty. We tested 20 chimpanzees (Pan troglodytes), 7 orangutans (Pongo pygmaeus), 5 bonobos (Pan paniscus), and 5 gorillas (Gorilla gorilla) in the trap-table--a task in which subjects have to pull one of two rakes prepositioned behind two rewards on a flat surface. One of the rewards is in front of a trap into which it will fall. We investigated the effect of trap type, tool type, the number of available tools, and reinforcement regime on performance. We replicated previous findings showing that apes failed to choose the correct rake above chance. However, when they could instead choose where to insert a single tool, around 80% of the apes solved the trap-table task in the first trial, revealing an important effect of task constraints on their performance.

Reproductive success is associated with age in many taxa, increasing in early life followed by reproductive senescence. In socially monogamous but genetically polygamous species, this generates the interesting possibility of differential trajectories of within-pair and extra-pair siring success with age in males. We investigate these relationships simultaneously using withinindividual analyses with 13 years of data from an insular house sparrow (Passer domesticus) population. As expected, we found that both within-and extra-pair paternity success increased with age, followed by a senescencelike decline. However, the age trajectories of within-and extra-pair paternity successes differed significantly, with the extra-pair paternity success increasing faster, although not significantly, in early life, and showing a delayed decline by 1.5 years on average later in life compared to within-pair paternity success. These different trajectories indicate that the two alternative mating tactics should have age-dependent pay-offs. Males may partition their reproductive effort between within-and extra-pair matings depending on their current age to reap the maximal combined benefit from both strategies. The interplay between these mating strategies and age-specific mortality may explain the variation in rates of extra-pair paternity observed within and between species.

Extra-pair paternity is the result of copulation between a female and a male other than her social partner. In socially monogamous birds, old males are most likely to sire extra-pair offspring. The male manipulation and female choice hypotheses predict that age-specific male mating behaviour could explain this old-over-young male advantage. These hypotheses have been difficult to test because copulations and the individuals involved are hard to observe. Here, we studied the mating behaviour and pairing contexts of captive house sparrows, Passer domesticus. Our set-up mimicked the complex social environment experienced by wild house sparrows. We found that middle-aged males, which would be considered old in natural populations, gained most extra-pair paternity. However, both, female solicitation behaviour and subsequent extra-pair matings were not associated with male age. Further, copulations were more likely when solicited by females than when initiated by males (i.e. unsolicited copulations). Male initiated within-pair copulations were more common than male initiated extra-pair copulations. To conclude, our results did not support either hypothesis regarding age-specific male mating behaviour. Instead, female choice, independent of male age, governed copulation success, especially in an extra-pair context. Post-copulatory mechanisms might determine why older males sire more extra-pair offspring.

Mate choice as one element of sexual selection can be sensitive to public information from neighbouring individuals. Here, we demonstrate that males of the livebearing fish Poecilia mexicana gather complex social information when given a chance to familiarize themselves with rivals prior to mate choice. Focal males ceased to show mating preferences when being observed by a rival (which prevents rivals from copying mating decisions), but this effect was only seen when focal males have perceived rivals as sexually active. In addition, focal males that were observed by a familiar, sexually active rival showed a stronger behavioural response when rivals were larger and thus, more attractive to females. Our study illustrates an unparalleled adjustment in the expression of mating preferences based on social cues, and suggests that male fish are able to remember and strategically exploit information about rivals when performing mate choice.

Evolutionary theory predicts that females seek extra‐pair fertilizations from high‐quality males. In socially monogamous bird species, it is often old males that are most successful in extra‐pair fertilizations. Adaptive models of female extra‐pair mate choice suggest that old males may produce offspring of higher genetic quality than young males because they have proven their survivability. However, old males are also more likely to show signs of reproductive senescence, such as reduced sperm quality. To better understand why old males account for a disproportionally large number of extra‐pair offspring and what the consequences of mating with old males are, we compared several sperm traits of both captive and wild house sparrows, Passer domesticus. Sperm morphological traits and cloacal protuberance volume (a proxy for sperm load) of old and young males did not differ substantially. However, old males delivered almost three times more sperm to the female's egg than young males. We discuss the possibility of a post‐copulatory advantage for old over young males and the consequences for females mated with old males.

21Extra-pair paternity is the result of copulation between a female and a male other than 22 her social partner. In socially monogamous birds, old males are most likely to sire 23 extra-pair offspring. The male manipulation and female choice hypotheses predict that 24 age-specific male mating behaviour could explain this old-over-young male 25advantage. These hypotheses have been difficult to test because copulations and the 26 individuals involved are hard to observe. Here, we studied the mating behaviour and 27 pairing contexts of captive house sparrows, Passer domesticus. Our set-up mimicked 28 the complex social environment experienced by wild house sparrows. We found that 29 middle-aged males, that would be considered old in natural populations, gained most 30 extra-pair paternity. However, both female solicitation behaviour and subsequent 31 extra-pair matings were unrelated to male age. Further, copulations were more likely 32 when solicited by females than those initiated by males (i.e. unsolicited copulations), 33 and unsolicited within-pair copulations were more common than unsolicited extra-34 pair copulations. To conclude, our results did not support either hypotheses regarding 35 age-specific male mating behaviour. Instead, female choice, independent of male age, 36 governed copulation success, especially in an extra-pair context and post-copulatory 37 mechanisms might determine why older males sire more extra-pair offspring. 38 39

Rates of multiple paternities were investigated in the sailfin molly (Poecilia latipinna), using eight microsatellite loci. Genotyping was performed for offspring and mothers in 40 broods from four allopatric populations from the south-eastern U.S.A. along a geographic stretch of 1200 km in west-east direction and approximately 200 km from north to south. No significant differences regarding rates of multiple paternities were found between populations despite sample populations stemming from ecologically divergent habitats. Even the most conservative statistical approach revealed a minimum of 70% of the broods being sired by at least two males, with an average of 1.80-2.95 putative fathers per brood. Within broods, one male typically sired far more offspring than would be expected under an assumed equal probability of all detected males siring offspring.