Testosterone and year-round territoriality in a tropical bird. Visual and nutritional food cues fine-tune timing of reproduction in a neotropical rainforest bird. Darwin s finches. Nature Publishing Group. Sturkie's Avian Physiology, pp.
Social instability increases testosterone year-round in a tropical bird.
A neotropical bird can measure changes in tropical photoperiod. Melatonin facilitates synchronization of sparrow circadian rhythms to light.