library_construction_protocol: A total of 6 migrant and 7 resident junco hypothalamii were punched and homogenized in RLT buffer containig 1% 2-Mercaptoethanol on ice. Total RNA was prepared using AllPrep DNA/RNA Universal Kit (Qiagen, Cat. # 80224). RNA integrity and concentration were determined using Agilent 2200 Tapestation System. The RNAseq libraries were generated using the TruSeq Stranded mRNA kit protocol. The integrity of the RNA was checked with Agilent Tapestation, samples with RIN >7 were used for library preparation. The mRNA was purified from 200ng of total RNA for each sample, after cDNA synthesis and adapter ligation, the library was amplified with 12 rounds of PCR cycles. The enriched and cleaned libraries were pooled and loaded on the sequencer.