Associated and disassociated patterns in hormones, song, behavior and brain receptor expression between life-cycle stages in male black redstarts, Phoenicurus ochruros

► Male black redstarts defend territories during breeding and nonbreeding. ► Testosterone is elevated during breeding, but low during nonbreeding. ► Song structure differs between seasons, but independent of testosterone. ► Song output in territorial context differs between seasons and depends on testosterone. ► Aromatase in preoptic area is up-regulated during breeding.