Bird species with larger-than-average brains have lower levels of a key stress hormone, an analysis of nearly 200 avian studies has concluded. Such birds keep their stress down by anticipating or learning to avoid problems more effectively than smaller-brained counterparts, researchers suggest.
Birds in the wild lead a stressful life. Constantly spotting predators lurking in the trees or sensing dramatic changes in temperature is essential for survival, but can leave a bird on the edge of a nervous breakdown. Reading these cues triggers changes in the birds’ metabolism, particularly increases in the stress hormone corticosterone. A sharp release of the hormone within one to two minutes after a cue triggers an emergency response and prepares birds to react quickly to the threat. However, regular exposure to the dangers of the wild and, hence, to high levels of this hormone has serious health consequences and shortens life expectancy.
Not all birds respond to stress in the same way, however, notes Daniel Sol, an ornithologist at the Centre for Ecological Research and Forestry Applications in Cerdanyola del Vallès, Spain. He and colleagues for years have looked at the differences between big-brained birds, such as crows and parrots, and those with smaller brains, such as chickens and quails. The former survive better in nature and also are more successful at establishing communities in new environments.