Signalling value of maternal and paternal melanism in the barn owl: implication for the resolution of the lek paradox

Abstract

Secondary sexual characters often signal qualities such as physiological processes associated with resistance to various sources of stress. When the expression of an ornament is not sex‐limited, we can identify the costs and benefits of displaying a trait that is typical of its own sex or of the other sex. Indeed, the magnitude and sign of the covariation between physiology and the extent to which an ornament is expressed could differ between males and females if, for instance, the regulation of physiological processes is sensitive to sex hormones. Using data collected over 14 years in the nocturnal barn owl Tyto alba, we investigated how nestling body mass covaries with a heritable melanin‐based sex‐trait, females displaying on average larger black feather spots than males. Independently of nestling sex, year and time of the day large‐spotted nestlings were heavier than small‐spotted nestlings. In contrast, the magnitude and sign of the covariation between nestling body mass and the size of parental spots varied along the day in a way that depended on the year and parental gender. In poor years, offspring of smaller‐spotted mothers were heavier throughout the resting period; in the morning, offspring sired by larger‐spotted fathers were heavier than offspring of smaller‐spotted fathers, while in the evening the opposite pattern was found. Thus, maternal and paternal coloration is differentially associated with behaviour or physiology, processes that are sensitive to time of the day and environmental factors. Interestingly, the covariation between offspring body mass and paternal coloration is more sensitive to these environmental factors than the covariation with maternal coloration. This indicates that the benefit of pairing with differently spotted males may depend on environmental conditions, which could help maintain genetic variation in the face of intense directional (sexual) selection. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 115, 376–390.

Differential fitness effects of moonlight on plumage colour morphs in barn owls

“…The IDs of the foster parents were included to account for repeated breeding of the same parents across several years. Fixed effects included moonlight, father plumage colouration and their interaction as well as factors known to affect nestling body mass: age (up to the 4 th power 75 ), hour (up to the 3 rd power), laying date (linear and quadratic), brood size, and rank within brood hierarchy. We only considered the colouration of the father given the larger male hunting effort.…”

Social huddling and physiological thermoregulation are related to melanism in the nocturnal barn owl

“…We propose that genes participating in melanogenesis such as melanocortins influence energy homeostasis. Alternatively, because highly spotted nestling barn owls invest more energy in growth than lightly spotted ones (Almasi and Roulin 2015), they may be less able to thermoregulate, and, as a consequence, they adjust their behaviour to ambient temperature. Larger-spotted nestlings of either sex grow faster and are heavier than smaller-spotted nestlings (Almasi and Roulin 2015), spot size being strongly genetically correlated with spot number (Roulin and Jensen 2015).…”

Weak and inconsistent associations between melanic darkness and fitness‐related traits in an insect

“…Naturally, however, such trade‐offs may differ among environments also for a variety of other reasons (e.g. Gonzales et al ., ; Almasi & Roulin, ).…”