Tuesday, April 5, 2011

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 NĂºria 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".


  1. What is CREAF? Interesting article on bird brain size, could you give an example of some of these birds?

  2. Personally, I'd think that the migratory birds would have the larger brain size because they are smart enough to get out of Ohio and head to the warmer, less volatile south. But really some migratory birds have strange but amazing abilities to migrate such as a certain species of hummingbird that only leaves when it somehow knows that its entire journey will have calm, favorable weather so it will not use any unnecessary energy, hopping from one island to the next down the eastern U.S. shore. Really fascinating!

  3. Do the smaller brains make the long flight less energy intensive, since the birds have less weight to carry?

  4. CREAF is the Centre for Ecological Research and Forestry Applications in Spain. A few birds that were studied for smaller brains include swallows and cuckoos.

    That is really interesting about the hummingbirds! It would definitely be logical that the birds with the knowledge to travel to unknown territories and face possible unforeseen challenges would have the larger brain. However, if you cut out the cognitive information required of residential birds that is not useful or needed in migratory birds a smaller brain makes sense.

    It would be a valid assumption that a smaller brain would make the long flight less energy intensive. Not only is there less physical weight for the bird to carry but the bird would be able to use its energy reservoirs for the actual flight. This would ultimately make the trip less taxing on their bodies (versus a residential bird trying to make the voyage).