Data from: SEX RATIO AND PLUMAGE CHARACTERISTICS OF JUVENILE AMERICAN ROBINS IN SUBURBAN AREAS OF THE ARKANSAS RIVER VALLEY

Included are plumage (pdata), sex ratio (bdata), and condition index (cdata) datasets analyzed in SEX RATIO AND PLUMAGE CHARACTERISTICS OF JUVENILE AMERICAN ROBINS IN SUBURBAN AREAS OF THE ARKANSAS RIVER VALLEY. A different submission includes the .Rmd (rmarkdown) file that has the code that was used with these datasets.<b>Abstract:</b> The sex ratio and plumage characteristics of juvenile American Robins (<i>Turdus migratorius</i>) are understudied. We sought to determine the fledging sex ratio (FSR) of the species and evaluate the relevance of sexual size dimorphism (SSD) and drought effects to the fledging sex ratio. We also used qualitative and quantitative assessments of juvenile plumage to gauge the feasibility of sex determination through plumage. The FSR was skewed towards females; 63% of 59 nestlings were female. There was not a significant difference in body condition between the sexes at fledging, even when drought effects were more severe. Male and female nestlings had substantial overlap in plumage characteristics, and we could not reliably distinguish between the sexes. Our findings support the hypothesis that SSD skews sex ratios towards the smaller sex, but more research is necessary to determine if that result is consistent with larger datasets and if other hypotheses are relevant to the FSR of the species. More advanced plumage analyses could help determine if the sexes of juvenile robins are visually distinct. Our study is the first to officially document the fledging sex ratio of American Robins and examine plumage differences between juvenile males and females.