Data from: Prevalence and implications of sex reversal in free-living birds

The ability to unequivocally identify the sex and reproductive status of
individuals is crucial across many fields of study. Recent evidence
indicates that avian sex determination is more flexible than once
believed, with sex-reversed individuals identified in domestic bird
populations—that is, individuals exhibiting gonadal and morphological
traits of one sex while possessing the chromosomal makeup of the opposite
sex. The presence of these individuals can challenge the reliability of
traditional sexing methods that rely solely on external morphology,
internal anatomy, or genetic markers. These methods, when used in
isolation, fail to identify sex-reversed or intersex individuals,
potentially overlooking their impact on population dynamics. In this
pioneering study, we investigated the prevalence of sex-reversed
individuals in five common free-living avian species in Queensland,
Australia. By comparing internal and external morphological
characteristics with PCR results from sex-linked molecular markers, we
identified sex-reversed individuals in all five species, with rates
ranging from 3% to 6%. Our findings suggest that sex reversal is a common
and potentially widespread phenomenon in avian species.