No sex-specific differences in the influence of high air temperatures during early development on nestling mass and fledgling survival in the Southern Pied Babbler (Turdoides bicolor)

Sex-biased mortality in response to environmental adversity during early development occurs in a number of bird species. The three most prominent theories proposed to explain sex-biased mortality in response to early-life adversity are that (1) the heterogametic sex (e.g. females in birds), (2) the larger sex (could be male or female depending on species) or (3) the sex with the more costly and complex endocrine system (e.g. males producing higher levels of testosterone) will suffer higher mortality compared with the other sex when exposed to challenging conditions (e.g. suboptimal weather during early development). We tested for sex-specific differences in the effects of very hot weather on nestling body mass and tarsus length, and survival of fledglings to nutritional independence in the Southern Pied Babbler Turdoides bicolor. The effect of exposure to high air temperatures did not differ by sex but had a consistently negative impact on nestling body mass, nestling tarsus length and fledgling survival, raising concerns about population replacement and the persistence of this species under rapidly advancing climate change.

Automated summary

Sex-biased mortality in response to environmental adversity during early development is prominent in various bird species. Three main theories propose that the heterogametic sex, the larger sex, or the sex with more complex endocrine system may experience higher mortality when faced with challenging conditions. Research on Southern Pied Babblers showed that high temperatures negatively impact nestling body mass, tarsus length, and fledgling survival, raising concerns about population replacement and species persistence under advancing climate change.