Brain regions associated with visual cues are important for bird migration.

Area of Science:

• Ornithology
• Neuroscience
• Evolutionary Biology

Background:

• Long-distance migratory birds exhibit smaller brain sizes compared to short-distance migrants or resident species.
• Brain regions involved in avian migration orientation are hypothesized to be affected by migration distance.

Purpose of the Study:

• To investigate if the reduction in brain size with migration distance is consistent across key brain regions involved in avian orientation.
• To identify specific brain regions that change in size relative to migration distance.

Main Methods:

• Comparative analysis of brain region sizes across 152 bird species from 61 avian families globally.
• Statistical modeling to assess the relationship between migration distance and the size of the telencephalon, optic lobe, cerebellum, and whole brain.

Main Results:

• A significant decrease in telencephalon and whole brain size was observed with increasing migration distance.
• The relative size of the optic lobe increased with migration distance, while cerebellum size remained unchanged.
• Body mass, whole brain size, optic lobe size, and wing aspect ratio collectively explained 46% of the variation in avian migration distance.

Conclusions:

• The findings suggest a specific neural adaptation, particularly enhanced visual processing capacity, for birds undertaking long-distance migrations.
• Visual acuity may be a crucial factor enabling birds to meet the ecological demands of long-distance migratory navigation.