Offspring sex ratio manipulation in chukar partridge, Alectoris chukar: effects of dexamethasone as a high-potent glucocorticoid

In avian species offspring sex ratio adjustment in response to environmental and hormonal factors is well-studied. However, inconsistencies in the literature regarding the impact of environmental stress and corticosterone on offspring sex ratios arise from varying hormone dosages. Herein, dexamethasone (DEX), a high-potent synthetic glucocorticoid, was orally administered at two dosages over 10 days to chukar partridges to investigate its effect on sex ratio as well as on circulating glucose, cholesterol and aminotransferase levels, which have been indirectly linked to sex ratio. Ninety-six female partridges were randomly assigned to four treatment groups: untreated, vehicle, low dose of DEX and high dose of DEX. Females in the low-dose group produced a higher proportion of male hatchlings compared with untreated and vehicle. However, the proportion of sons in the high-dose group birds did not differ significantly from those groups. No significant differences were found in egg production and hatchability, suggesting no sex-specific embryo mortality. Group differences in glucose concentrations showed a similar pattern of statistical significance as that of sex ratio that, in turn, correlated with glucose. Our findings indicate a dose-dependent effect of glucocorticoids on avian sex ratio and suggest that glucose may be part of the underlying mechanism.