Under the Tanzanian skies, some thrush nightingale males reside in close proximity to each other, a striking contrast to their territorial behavior during breeding season in temperate zones. With the end of winter, a dual transformation unfolds in the birds: the emergence of full songs and territorial behavior. Over five years, researchers from the Max Planck Institute for Biological Intelligence decoded their connection in the birds’ winter quarters. They could show that the annual melodious development of song intertwines with territoriality, both triggered by surging testosterone levels at the nearing end of winter.