The question of why maternal stress influences offspring phenotype is of significant interest to evolutionary physiologists. Al- though embryonic exposure to maternally derived glucocorticoids (i.e., corticosterone) generally reduces offspring quality, effects may adaptively match maternal quality with offspring demand. We present results from an interannual field experiment in European starlings (Sturnus vulgaris) designed explicitly to examine the fitness conse- quences of exposing offspring to maternally derived stress hormones. We combined a manipulation of yolk corticosterone (yolk injections) with a manipulation of maternal chick-rearing ability (feather clip- ping of mothers) to quantify the adaptive value of corticosterone- induced offspring phenotypes in relation to maternal quality. We then examined how corticosterone-induced "matching" within this current reproductive attempt affected future fecundity and maternal survival. First, our results provide support that low-quality mothers transferring elevated corticosterone to eggs invest in daughters as predicted by sex allocation theory. Second, corticosterone-mediated sex-biased investment resulted in rapid male-biased mortality re- sulting in brood reduction, which provided a better match between maternal quality and brood demand. Third, corticosterone-mediated matching reduced investment in current reproduction for low-quality mothers, resulting in fitness gains through increased survival and future fecundity. Results indicate that the transfer of stress hormones to eggs by low-quality mothers can be adaptive since corticosterone- mediated sex-biased investment matches the quality of a mother to offspring demand, ultimately increasing maternal fitness. Our results also indicate that the branding of the proximate effects of maternal glucocorticoids on offspring as negative ignores the possibility that short-term phenotypic changes may actually increase maternal fitness.

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The Adaptive Value of Stress‐Induced Phenotypes: Effects of Maternally Derived Corticosterone on Sex‐Biased Investment, Cost of Reproduction, and Maternal Fitness

https://pure.rug.nl/ws/files/6764847/2011NeurosciBiobehavRevHenriksen.pdf

Prenatal stress in birds: pathways, effects, function and perspectives.

Exposure to maternally derived glucocorticoids during embryonic development impacts offspring phenotype. Although many of these effects appear to be transiently 'negative', embryonic exposure to maternally derived stress hormones is hypothesized to induce preparative responses that increase survival prospects for offspring in low-quality environments; however, little is known about how maternal stress influences longer-term survival-related performance traits in free-living individuals. Using an experimental elevation of yolk corticosterone (embryonic signal of low maternal quality), we examined potential impacts of embryonic exposure to maternally derived stress on flight performance, wing loading, muscle morphology and muscle physiology in juvenile European starlings (Sturnus vulgaris). Here we report that fledglings exposed to experimentally increased corticosterone in ovo performed better during flight performance trials than control fledglings. Consistent with differences in performance, individuals exposed to elevated embryonic corticosterone fledged with lower wing loading and had heavier and more functionally mature flight muscles compared with control fledglings. Our results indicate that the positive effects on a survival-related trait in response to embryonic exposure to maternally derived stress hormones may balance some of the associated negative developmental costs that have recently been reported. Moreover, if embryonic experience is a good predictor of the quality or risk of future environments, a preparative phenotype associated with exposure to apparently negative stimuli during development may be adaptive.

/pdf/juveniles-exposed-to-embryonic-corticosterone-have-enhanced-1oc76gwez1.pdf

Juveniles exposed to embryonic corticosterone have enhanced flight performance

https://pure.sruc.ac.uk/ws/files/15113737/14187.pdf

Early experiences matter: A review of the effects of prenatal environment on offspring characteristics in poultry

SUMMARY In many birds, testes undergo dramatic annual changes in size and, as such, are among the most anatomically and physiologically plastic organs found in adult vertebrates. Adult testicular function is modulated by a myriad of external factors and orchestrated by numerous hormones that together enable birds to adapt to and breed in diverse habitats worldwide. These factors have generated a wide range of avian reproductive strategies, which has further shaped testicular structure and function. This chapter describes the mechanisms that control avian exocrine and endocrine testicular functions. It analyzes how these functions are regulated by ecological and behavioral factors and presents an overview of how environmental information is integrated and transduced into appropriate gonadal responses. It also discusses testicular dysfunction and the potential effects of anthropogenic disturbances on testis function. The chapter emphasizes areas where knowledge is lacking or incomplete, with the hope of fostering additional research on this exciting and fruitful area of avian biology.

/pdf/avian-testicular-structure-function-and-regulation-2dadfauq8y.pdf

Avian testicular structure, function, and regulation

Cloacal Gland and Gonadal Photoresponsiveness in Male Japanese Quail Selected for Divergent Plasma Corticosterone Response to Brief Restraint

Maternal Corticosterone Further Reduces the Reproductive Function of Male Offspring Hatched from Eggs Laid by Quail Hens Selected for Exaggerated Adrenocortical Stress Responsiveness

C. A. Cole

Papers

Cloacal Gland and Gonadal Photoresponsiveness in Male Japanese Quail Selected for Divergent Plasma Corticosterone Response to Brief Restraint

Maternal Corticosterone Further Reduces the Reproductive Function of Male Offspring Hatched from Eggs Laid by Quail Hens Selected for Exaggerated Adrenocortical Stress Responsiveness