Homing pigeons as a model for the influence of experience on brain composition-including considerations on evolutionary theory

The brain of homing pigeons seems to be functionally adapted to homing with e.g., larger hippocampi and olfactory bulbs. Furthermore, functional lateralization occurs as well in homing pigeons. Recently, the investigation of the influence of navigational experience on brain composition and lateralization revealed larger hippocampi in homing pigeons with navigational experience compared to inexperienced homing pigeons. Additionally, there are several brain structures in homing pigeons that show a volumetrical lateralization, whereas homing pigeons with navigational experience show a more lateralized brain than pigeons without navigational experience. This gives more insights in the neuronal basis of orientation and brain development in general but demonstrates as well its complexity. Plasticity and lateralization are much more correlated with individual life history than assumed up to date and have to be more considered in comparative research of evolution

Morphometric analysis of telencephalic structure in a variety of neognath and paleognath bird species reveals regional differences associated with specific behavioral traits

Birds exhibit a huge array of behavior, ecology and physiology, and occupy nearly every environment on earth, ranging from the desert outback of Australia to the tropical rain forests of Panama. Some birds have adopted a fully nocturnal lifestyle, such as the barn owl and kiwi, while others, such as the albatross, spend nearly their entire life flying over the ocean. Each species has evolved unique adaptations over millions of years to function in their respective niche. In order to increase processing power or network efficiency, many of these adaptations require enlargements and/or specializations of the brain as a whole or of specific brain regions. In this study, we examine the relative size and morphology of 9 telencephalic regions in a number of Paleognath and Neognath birds and relate the findings to differences in behavior and sensory ecology. We pay particular attention to those species that have undergone a relative enlargement of the telencephalon to determine whether this relative increase in telencephalic size is homogeneous across different brain regions or whether particular regions have become differentially enlarged. The analysis indicates that changes in the relative size of telencephalic regions are not homogeneous, with every species showing hypertrophy or hypotrophy of at least one of them. The three-dimensional structure of these regions in different species was also variable, in particular that of the mesopallium in kiwi. The findings from this study provide further evidence that the changes in relative brain size in birds reflect a process of mosaic evolution