Search

Avian eggshell pigmentation may provide information about a female's physiological condition, in particular her state of oxidative balance. Previously we found that female House Wrens (Troglodytes aedon Vieillot, 1809) with lighter, less-maculated, and redder ground-colored shells were older and produced heavier offspring than females laying more-maculated and browner eggs. The strong pro-oxidant protoporphyrin is responsible for this species' eggshell pigmentation, so differences in pigmentary coloration may be related to eggshell protoporphyrin content and reflect female oxidative balance and condition during egg formation. Therefore, we tested the assumption that egg-surface coloration is related to the amount of protoporphyrin in the shell matrix. We analyzed digital photographs of eggs to determine maculation coverage as a measure of the overall ground coloration of the egg and its red-, green-, and blue-channel pixel values. Pigments were then extracted from these same eggs and analyzed using high-performance liquid chromatography. There was a strong, positive relationship between eggshell redness and protoporphyrin content of eggshells, but no relationship between percent maculation and protoporphyrin content. Thus, when older, larger females deposit more protoporphyrin in their eggshells, this may reflect a tolerance for high levels of circulating protoporphyrin or an effective mechanism for off-loading protoporphyrin into the eggshell matrix. Key words: House Wren, Troglodytes aedon, eggs, female quality, HPLC, eggshell pigmentation. La pigmentation des coquilles d'oeuf d'oiseaux pourrait fournir de l'information sur l'état physiologique des femelles, notamment sur leur équilibre oxydatif. Nous avons déjà relevé que des troglodytes familiers (Troglodytes aedon Vieillot, 1809) femelles dont les coquilles d'oeus sont plus claires, moins maculées et de couleur de base plus rouge sont plus âgées et produisent des rejetons plus lourds que les femelles qui pondent des oeufs plus maculés et bruns. Comme la protoporphyrine, un puissant pro-oxydant, est responsable de la pigmentation de la coquille des oeufs de cette espèce, des différences de coloration pigmentaire pourraient être reliées à la teneur en protoporphyrine de la coquille et refléter l'équilibre oxydatif et l'état physiologique des femelles durant la formation des oeufs. Nous avons donc vérifié l'hypothèse selon laquelle la coloration de la surface des oeufs est reliée à la quantité de protoporphyrine dans la matrice de la coquille. Nous avons analysé des photographies numériques d'oeufs pour déterminer la couverture de tâches (maculation) comme mesure de la coloration de base globale de l'oeuf, et les valeurs des pixels des canaux rouges, verts et bleus. Des pigments ont ensuite été extraits de ces mêmes oeufs et analysés par chromatographie liquide à haute performance. Une forte relation positive est relevée entre l'intensité de la couleur rouge et la teneur en protoporphyrine des coquilles d'oeufs, alors qu'aucune relation n'est notée entre le pourcentage de tâches et la teneur en protoporphyrine. Ainsi, le dépôt par des femelles plus âgées et plus grandes de plus importantes quantités de protoporphyrine dans les coquilles de leurs oeufs pourrait refléter une tolérance à des concentrations élevées de protoporphyrine en circulation ou un mécanisme efficace de délestage de protoporphyrine vers la matrice des oeufs. [Traduit par la Rédaction] Mots-clés : troglodyte familier, Troglodytes aedon, oeufs, qualité des femelles, CLHP, pigmentation des coquilles d'oeuf., Introduction Eggshell pigmentation is an extended phenotypic trait of female birds, one that may provide information about a female's underlying physiological condition (Moreno and Osorno 2003; Moreno et al. 2006; [...]

The evolution of nuptial gifts has traditionally been considered a harmonious affair, providing benefits to both mating partners. There is growing evidence, however, that receiving a nuptial gift can be actively detrimental to the female. In decorated crickets (Gryllodes sigillatus), males produce a gelatinous spermatophylax that enhances sperm transfer but provides little nutritional benefit and hinders female post-copulatory mate choice. Here, we examine the sexually antagonistic coevolution of the spermatophylax and the female feeding response to this gift in G. sigillatus maintained in experimental populations with either a male-biased or female-biased adult sex ratio. After 25 generations, males evolving in male-biased populations produced heavier spermatophylaxes with a more manipulative combination of free amino acids than those evolving in female-biased populations. Moreover, when the spermatophylax originated from the same selection regime, females evolving in male-biased populations always had shorter feeding durations than those evolving in female-biased populations, indicating the evolution of greater resistance. Across populations, female feeding duration increased with the mass and manipulative combination of free amino acids in the spermatophylax, suggesting sexually antagonistic coevolution. Collectively, our work demonstrates a key role for interlocus sexual conflict and sexually antagonistic coevolution in the mating system of G. sigillatus. [ABSTRACT FROM AUTHOR]

The operational sex ratio (OSR) is a key component influencing the magnitude of sexual selection driving the evolution of male sexual traits, but males often also retain the ability to plastically modulate trait expression depending on the current environment. Here we employed an experimental evolution approach to determine whether the OSR affects the evolution of male calling effort in decorated crickets, a costly sexual trait, and whether plasticity in calling effort is altered by the OSR under which males have evolved. Calling effort of males from 2 selection regimes maintained at different OSRs over 18–20 generations (male vs. female biased) was recorded at 2 different levels of perceived competition, in the absence of rivals or in the presence of an experimentally muted competitor. The effect of the OSR on the evolution of male calling effort was modest, and in the opposite direction predicted by theory. Instead, the immediate competitive environment strongly influenced male calling effort as males called more in the presence of a rival, revealing considerable plasticity in this trait. This increased calling effort came at a cost, however, as males confined with a muted rival experienced significantly higher mortality. [ABSTRACT FROM AUTHOR]

In recent years, temperatures have increased globally, and nestlings of many bird species are likely regularly exposed to increased temperatures both pre‐ and post‐natally. Even small increases in nest temperature during incubation affect offspring growth and survival in a variety of species, one cause of which is thought to be increased production of pro‐oxidants in embryos and nestlings. Defences marshalled in response to this oxidative stress could, in turn, result in trade‐offs that lead to reduced survival or growth. If so, any downstream negative effects on nestlings of increased ambient temperatures during incubation could be counteracted by increasing their antioxidant intake. We predicted, therefore, that dietary supplements of an antioxidant would reduce or eliminate any detrimental effects on nestling growth and survival of experimentally increased nest temperature during the incubation period. We employed a split‐brood design in which we increased the nest temperature of entire clutches and, after hatching, provided dietary supplements of the antioxidant vitamin E to half of the nestlings within broods. We also recorded female incubation and provisioning behaviour to control for the possibility that heating nests might also influence maternal behaviour. There was a significant interaction between nestbox heating treatment and vitamin E treatment in their effect on nestling mass, a trait that is positively correlated with survival and future reproductive success in the study population. Vitamin E supplementation promoted increased nestling mass in heated nests, whereas it had the opposite effect in control nests but these effects were weak. Heating significantly affected female incubation behaviour, with females in heated nestboxes investing less in incubation than those in unheated boxes. These results suggest that within at least some range of expected increased ambient temperatures during the 21st century, effects of climate change on nestling bird development can be mitigated by adjustments in female incubation behaviour. [ABSTRACT FROM AUTHOR]