Mothers adjust offspring sex to match the quality of the rearing environment

Abstract

Theory predicts that mothers should adjust offspring sex ratios when the expected fitness gains or rearing costs differ between sons and daughters. Recent empirical work has linked biased offspring sex ratios to environmental quality via changes in relative maternal condition. It is unclear, however, whether females can manipulate offspring sex ratios in response to environmental quality alone (i.e. independent of maternal condition). We used a balanced within-female experimental design (i.e. females bred on both low-and high-quality diets) to show that female parrot finches (Erythrura trichroa) manipulate primary offspring sex ratios to the quality of the rearing environment, and not to their own body condition and health. Individual females produced an unbiased sex ratio on high-quality diets, but over-produced sons in poor dietary conditions, even though they maintained similar condition between diet treatments. Despite the lack of sexual size dimorphism, such sex ratio adjustment is in line with predictions from sex allocation theory because nutritionally stressed foster sons were healthier, grew faster and were more likely to survive than daughters. These findings suggest that mothers may adaptively adjust offspring sex ratios to optimally match their offspring to the expected quality of the rearing environment.

Relationship of Hemoglobin Concentration to Packed Cell Volume in Avian Blood Samples

“…Apart from parasite-related effects, variation in the hemoglobin concentration of nestling Blue Tits and Great Tits (Parus major) reflected differences in trophic conditions between seasons and sites (Bańbura et al 2007, Kaliński et al 2009). Similarly, the experimental study of Pryke and Rollins (2012) demonstrated positive effects of diet quality on hemoglobin concentrations in nestling Blue-faced Parrot Finches (Erythrura trichroa). Unusually low hemoglobin concentrations were also recorded in Great Tit chicks exposed to high environmental pollution (Nyholm et al 1995).…”

Spatial variation in haemoglobin concentration of nestling Blue Tits (Cyanistes caeruleus): a long-term perspective

“…It reflects the presence of pathogens and parasites, as well as the nutritional status of organism (a drop in haemoglobin concentration suggests nutritional deficiency ;Campbell 1995;Simon et al 2004;Kasprzyk et al 2006;Słomczyński et al 2006). All those features support the use of the haemoglobin level as a relatively reliable indicator of physiological condition in field and experimental studies on birds (Stevens 1996;Kilgas et al 2006a;Kaliński et al 2009Kaliński et al , 2012Pyrke and Rollins 2012;Lill et al 2013;Minias 2014;Minias et al 2014;Glądalski et al 2015a). But it is important to emphasize that some recent studies recommend caution when using blood characteristics to evaluate physiological condition in some species (Fair et al 2007;Lill et al 2013;Minias 2015;Johnstone et al 2015).…”

High glucose concentrations are associated with symptoms of mild anaemia in Whiskered Terns: consequences for assessing physiological quality in birds

“…Similarly to glucose concentration, blood haemoglobin level is commonly used in both field and experimental studies on birds as a proxy of physiological condition. An experimental study by Pyrke and Rollins (2012) demonstrated a positive impact of diet quality on haemoglobin concentrations in nestling Parrot Finches Erythrura trichroa. Similarly, haemoglobin concentrations of Great Tit Parus major nestlings were found to reflect differences in trophic conditions between seasons and sites (Bańbura et al 2007).…”