Migratory birds have smaller brains

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Washington, April 30 (ANI): Scientists have shed new light on the evolution of brain size in birds.

It has been known for some time that migratory birds have smaller brains than their resident relatives. Now, a new study by tesearchers at Centre for Ecological Research and Forestry Applications (CREAF, a Universitat Autonoma de Barcelona-affiliated centre) looks into the reasons and concludes that the act of migrating leads to a reduced brain size.

The authors point to the fact that the causes could be due to a need to reduce energetic, metabolic and cognitive costs.

To reach these conclusions, scientists reconstructed the evolutionary history of one of the most numerous orders of birds, the passeriformes, a group that includes swallows, tits and crows.

Understanding brain evolution is something that has interested scientists since the times of Charles Darwin, who considered that the large size of a human brain went hand in hand with the exceptional cognitive capacities of our species.

One of the classic explanations is the protective brain theory, which suggests that a large brain -in comparison to body size- makes learning easier. This protects individuals from changes in the environment, such as those produced by changes in season.

In the case of birds however not all species respond to seasonal changes in the same way. Migratory birds avoid these changes by travelling to less inhospitable places when conditions worsen.

This is the strategy followed by swallows or cuckoos. Resident bird species stay in the same area throughout the year and face strong environmental fluctuations. Tits and crows belong to this group.

Previous studies showed that both strategies are related to differences in brain size. The problem however is that it is often difficult to discern the causes and consequences of the differences observed.

By analysing data from 600 passerine species in regions ranging from tropical to artic, CREAF researchers Daniel Sol and Nuria Garcia, together with scientists from Canada and England, confirm that migratory birds have smaller brains than their resident counterparts.

The question now is whether brain size determines lifestyle (migratory or resident) or whether lifestyle determines the size of the brain.

According to the protective brain theory, being a resident bird makes it easier for the brain to grow and this for example facilitates acquiring alternative food-finding strategies for the winter months.

Nevertheless, the study reveals the complete opposite and points to the fact that being a migratory bird is what makes these birds have smaller brains.

The study has been published in the March edition of the journal PLoS One. (ANI)

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