Brighter yellow blue tits make better parents

Abstract

Whether or not bird ornaments are a signal for direct (e.g. good parents) or indirect (e.g. good genes) benefits to prospective partners in sexual selection is controversial. Carotene coloration in Parus species is directly related to the ingestion of caterpillars, so that a brightly carotene-coloured tit may be signalling its ability to find caterpillars, a main high-quality food source for good fledgling development, and hence its parental abilities. If carotene-based plumage coloration is related to the good-parent hypothesis, we predict that yellow plumage brightness of tit fathers should be positively correlated to their investment in offspring provisioning. Here, we use cross-fostering experiments in blue tits (Parus caeruleus) to show that chick development (as measured by tarsus length) is related to yellowness of the foster father, but not to that of the genetic parents. Using these data, we were able to measure, for the first time to our knowledge, the separate contribution of genetic and environmental factors (i.e. parental plumage coloration) to chick development, and hence parental investment. Our data, which relate carotenoid coloration to models of good parents, and data from other authors, which relate ultraviolet coloration to good-genes models, stress that different kinds of coloration within an individual may provide different units of information to prospective females.

Carotenoid-based plumage colouration is associated with blood parasite richness and stress protein levels in blue tits (Cyanistes caeruleus)

“…Birds being able to develop a conspicuous plumage during the moult could show a better health status in the next spring, especially because most of these blood parasite infections are chronic with birds suVering relapses while breeding (Valkiínas 2005). Birds in poor health would be less eYcient in acquiring carotenoid-rich food (Hill 1991(Hill , 1992Senar et al 2002) and consequently would exhibit a paler plumage. A previous experiment in the same study population showed that females medicated with primaquine did not vary in body condition during the breeding season, whereas body condition was reduced in control females during the same period, suggesting that blood parasites have negative eVects on female condition (Merino et al 2000).…”

“…As our methods of colour estimates had reasonably low measurement error to suYciently describe inter-individual diVerences in carotenoid chroma [repeatability (Lessells and Boag 1987) of two consecutive measurements R i = 0.66, F 13,14 = 4.83; P < 0.01], just one spectral measurement was taken from each individual in 2007. As in other studies based on the use of spectrophotometers not including UV reXectance (Figuerola et al 1999;Senar et al 2002;Hidalgo-García 2006;Ferns and Hinsley 2008), we face a potential problem since blue tit visual perception extends into the UV range of the spectrum (Hunt et al 1998;Örnborg 2002). However, our main aim is to explore whether carotenoid chroma as experienced by human observers is associated with some health parameters of birds.…”

“…It is a slightly sexually dichromatic species, males being more intensely coloured than females (Cramp 1998). In blue tit males, yellow carotenoid-based colouration has been shown to indicate parental investment (Senar et al 2002), while in females it reXects their reproductive capacity (Doutrelant et al 2008). Moreover, there is assortative mating by this trait (Hidalgo-García 2006;Ferns and Hinsley 2008), which suggests that yellow plumage colouration might be sexually selected in both sexes.…”

Direct versus indirect sexual selection: genetic basis of colour, size and recruitment in a wild bird

“…However, in the study by Delhey et al (2003), it was in fact the less ornamented males that gained extra-pair offspring, so these results were inconsistent with the other studies supporting indirect models, in that the sign of the correlation was in the opposite direction. Evidence of a role for direct benefits in the blue tit comes from studies in which the carotenoid based coloration of foster males was correlated with the body size of their foster chicks (Senar et al 2002).…”

Origin-related differences in plumage coloration within an island population of great tits (Parus major)

“…As carotenoids are not only used for coloration, but also play an important role in many physiological processes (Olson and Owens 1998), variation in carotenoid-based coloration is often considered to be a reliable predictor of individual quality. For example, individuals with plumage that contains more carotenoids are healthier (e.g., Hõrak et al 2001;Saks et al 2003b), survive better (Hill 1991;Hõrak et al 2001), are in better nutritional condition (Hill and Montgomerie 1994), or provide more care for their young (Senar et al 2002).…”