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Understanding the mechanisms that influence variation in sexually selected ornaments in seabirds has been challenging owing to the difficulty of capturing and sampling individuals outside of the breeding period when ornaments are usually grown. Stable carbon (δ13C) and nitrogen (δ15N) isotopes were used to examine the influence of pre‐breeding diet composition on ornament size in the Rhinoceros Auklet...
In behavioural studies it has been common to quantify plumage colours or ornaments over a range of dates and link them to fitness characteristics without accounting for seasonal changes in these traits. Such changes are likely to be widespread among birds, yet we lack assessments of this variability within individuals. We studied both within‐ and between‐individual temporal changes in Great Tit Parus major...
Intrasexual competition for reproduction is thought to be an important factor in the evolution of ornaments and weapons in males. However, the evolution of morphologically similar traits in females is often explained through other mechanisms, and the role of intrasexual competition in female trait elaboration has received little attention. Here, we explore the factors associated with female trait...
When multiple ornaments are expressed in both sexes, they are generally assumed to be maintained by mutual sexual selection and have a function in mate choice. In the Long‐tailed Finch Poephila acuticauda both sexes exhibit multiple ornaments that vary in their expression in either size (pintail and throat patch) or colour (bill) between individuals and sexes. We assessed whether these ornaments are...
Birds breeding on islands often exhibit lower rates of extrapair paternity than their mainland counterparts, perhaps explained by low genetic variation, ‘slower’ life histories and reduced sexual selection in island populations. Extrapair paternity was apparent in 39% (12/19) of broods, and encompassed 15% (21/137) of nestlings, in a population of African Blue Tits Cyanistes teneriffae, in Tenerife,...
The fitness‐related consequences of egg size, independent of the influences of parental quality, are poorly understood in altricial birds. Not only can egg size and parental quality influence growth and survival, but each could influence the development of condition‐dependent plumage coloration in offspring. The Eastern Bluebird Sialia sialis is an altricial, multi‐brooded, cavity‐nesting passerine...
Ornamental traits typically advertise individual condition and can be costly to maintain. Plumage maintenance behaviour can increase plumage quality and positively influence female mate preference. We investigated this prediction by performing female mate‐choice trials and measuring male plumage maintenance behaviour in the European Serin Serinus serinus. More colourful males spent more time in plumage...
The determinants and function of pigmentation of feathers and other tissues have been the focus of a large number of studies, particularly with respect to socio‐sexual communication. However, many birds exhibit depigmented white spots or bars on their feathers whose function is poorly understood. Here we assess whether white feather spots reflect phenotypic condition at the time of moult by investigating...
Melanin‐based plumage ornaments have been shown to play an important role in male–male competition, but also influence inter‐sexual communication. Consequently, ornaments may be associated with reproductive effort of both males and females. Females mated to males with larger melanin ornaments may acquire access to better territories or benefit from increased paternal care. Here we investigated whether...
Female song in passerine birds may be more common than traditionally assumed, but it is not well‐documented or understood, especially in migratory species. We describe the first evidence of sex‐specific songs produced by female Prothonotary Warblers, as well as the results of playback trials aimed at exploring the adaptive function (if any) of this female‐specific vocalization. Based on the behaviour...
There is increasing evidence that melanin‐based plumage coloration correlates with different components of fitness and that it may act as a social or sexual signal of individual quality. We analysed variation in melanin pigmentation in the outermost tail feathers of the Common Snipe Gallinago gallinago. During courtship flights, male Snipe use their outermost tail feathers to generate a drumming sound,...
Members of the avian family Pipridae (manakins) have served as a model system for studies aimed at understanding cooperation among individuals, traits involved in sexual selection and the evolution of female preferences. These studies rely on a detailed natural history baseline, yet multiple manakin taxa remain unstudied, precluding comparative analyses and assessment of geographical variation. The...
In the context of sexual selection, animals have developed a variety of cues conveying information about the sex of an individual to conspecifics. In many colonial seabird species, where females and males are monomorphic and do not show obvious differences in external morphology, acoustic cues are an important signal for individual and sex recognition. Here, we study the vocal and morphological sex...
For the past several decades it has been proposed that birds show latitudinal variation in song complexity. How universal this variation may be and what factors generate it, however, are still largely unknown. Furthermore, while migration is confounded with latitude, migratory behaviour alone may also be associated with variation in song complexity. In this paper we review the literature to assess...
Sexually selected colour traits of bird plumage are widely studied. Although the plumage is replaced only at one or two yearly moults, plumage colour has long been shown to change between moults. Nevertheless, most studies measure colour weeks to months after the courtship period, typically at nestling rearing, and it is unclear whether these measurements yield relevant data concerning the primary...
Several factors shape lifetime reproductive success, including genetic background, body condition, environmental conditions and ecological interactions such as parasitism. Adults often show higher reproductive success than their young conspecifics, especially in long‐lived bird species, and this may be explained by the cumulative effects of an increase in reproductive experience and the selection...
Melanin is the most common pigment in avian plumage and has various functions, including signalling individual condition, social status, aiding in camouflage and strengthening feathers. To date, most research focusing on melanin‐based colours has focused on eumelanin black and pheomelanin rusty traits. The occurrence and function of grey melanin‐based coloration, however, remains largely unstudied...
There is growing evidence that engaging in extra‐pair copulations may be a strategy by which females can modify their initial mate choice if they are constrained by primary choice of the social mate. Several factors such as genetic similarity and adult phenotypic traits can affect extra‐pair paternity (EPP) patterns, but the relative importance of these factors may vary among species. Moreover, interactive...
Several bird species construct multiple nests within a single breeding season that are not used for egg‐laying. This behaviour has puzzled researchers for over 100 years, as nests are costly in time and energy to build, and there is no apparent adaptive function. We review the empirical evidence for several suggested non‐exclusive functions and examine the plausibility of each. These functions are:...
Post‐mating courtship displays are often viewed as forms of sexual selection that allow individuals to assess fitness benefits from their mates based on honest signalling. However, display costs are not always easy to identify and quantify. Before each breeding attempt, male Black Wheatears Oenanthe leucura carry tens of heavy stones with the bill to form piles near the nest. The consequent increase...
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