In 1849, Berthold demonstrated that testicular secretions are necessary for aggressive
behavior in roosters. Since then, research on the neuroendocrinology of aggression has been …

Evolutionary biologists tend to approach the study of the natural world within a framework of
adaptation, inspired perhaps by the power of natural selection to produce fitness …

Blood sampling is often critical for answering a variety of questions about wild birds. However,
it is important to assess the impacts, if any, of blood collection on wild birds. Here, we …

In fluctuating environments, mothers may enhance the fitness of their offspring by adjusting
offspring phenotypes to match the environment they will experience at independence. In free-…

Urban ecosystems are rapidly expanding throughout the world, but how urban growth affects
the evolutionary ecology of species living in urban areas remains largely unknown. Urban …

In male song sparrows (Melospiza melodia), territorial challenges during the breeding season
can rapidly increase circulating levels of testosterone (T). During the non-breeding season…

Bacterial diversity within animals is emerging as an essential component of health, but it is
unknown how stress may influence the microbiome. We quantify a proximate link between the …

Cultural evolution can result in changes in the prevalence not only of different learned song
types within bird populations but also of different segments within the song. Between 1980 …

Determining how events interact across stages of the annual cycle is critical for understanding
the factors that affect individual fitness. However, there is currently little information …

Stress has well-known effects on adrenal glucocorticoid secretion, and chronic elevation of
glucocorticoids can have detrimental effects on the brain. Dehydroepiandrosterone (DHEA), …