Genetic sampling and library preparation
Sample site locations were chosen to maximize sampling coverage across the breeding and nonbreeding ranges of the American Redstart. We used genetic samples from a total of 330 individuals: 182 individuals from 16 locations across the breeding range and 148 individuals from 15 locations in the nonbreeding range (Table S1). Sample collection occurred between 1993 and 2022 and consisted of either blood from brachial venipuncture or feathers. We extracted DNA from blood samples using the standard protocol for Qiagen DNEasy Blood and Tissue Kits and we modified the protocol to maximize DNA yield from feathers. Whole genome sequencing libraries were prepared following modifications of Illumina’s Nextera Library Preparation protocol . Pooled libraries were sequenced on eight HiSeq 4000 lanes at Novogene Corporation Inc with a target sequencing depth of 2X per individual.