Smaller Brains in Migratory Birds

Before I was even finished taking the assessment test I realized that I knew very little about ecology and the behavior of animals in general. Yeah, I got a taste of it in the early Biology classes but I never needed to take the specialized classes of Ecology or Zoology to get where I am now. So, while looking at various sites and blogs on ecology and animal behavior, I came across a really interesting article on the differing brain sizes in migratory birds versus residential birds and I just had to read more.

There are two major questions scientists asked about the brain size of these birds: is the smaller brain a result of migration or does a smaller brain predestine a bird to migrate? Along with their colleagues, Daniel Sol and Núria Garcia who are CREAF researchers studied 600 passerine species with varying habitats. Within these 600 species, Sol and Garcia found that migratory birds do indeed have smaller brains than residential birds who tough out the sometimes harsh seasonal changes. They also concluded that the decreased brain size is a direct result of migration--contrary to the previously accepted 'protective brain theory'.

As earlier studies have shown, having a larger brain is more desirable than having a smaller brain due to it's large cognitive holding capacity. This theory holds true for residential birds who remain in their habitat from birth until death and who need to constantly learn how to stay alive, search for food, and fend off predators. However, with migratory birds, familiarity and knowledge of their surroundings is not as important since their stay in that area is only temporary. The cost-benefit idea is also a valid explanation of the smaller brains in these birds. The amount of energy they would spend learning the only transitory habitat could be put to better use during their travels. Sol and Garcia stated that "for these species, their innate behavior can be more useful than learned behavior".

As a follow up to their research, the researchers added that an analysis of the pallium and telencephalon in the bird brains would be beneficial to their conclusions since these areas are "involved in learning and behavior innovation processes".