File S1 Supplemental Material contains extended material and methods for Fallahshahroudi et al. This includes information regarding generation of the advanced backcross, analysis of population genetics, gene expression, hormone and metabolic rate, and behavior data. Furthermore, File S1 supplemental material file contains tables including PCR primer sequences, accession numbers of the sample used in European Nucleotide Archive, and haplotype sharing in the TSHR gene between White Leghorn and other populations. File S2 Dataset includes all data used in the analyses and producing the figures, including genotypes, gene expression, metabolic rate, hormone levels, and all measured behaviors.