From a million giant wildebeest crossing political borders in the Serengeti to a minuscule bacterial colony moving across an agar gel in a petri-plate, migratory behaviour can be seen at all scales. Migration has evolved multiple times independently in many animal groups, such as birds, fish, mammals (including marine mammals and bats), reptiles (e.g. sea turtles), amphibians, insects and marine invertebrates. Although the evolution of migration in most cases is a response to seasonal fluctuations, its occurrence and extent depends on many physical, geographical, historical, and ecological factors which are likely to facilitate and/or constrain the evolution of migration. My thesis work broadly revolves around understanding the pattern of evolution of migration in birds. I use a meta data analysis approach to estimate global patterns in evolutionary history using ancestral character state reconstruction.

In my study, we target two aspects of migration: Group migration (where individuals of a species migrate together in groups) and Long-distance migration. In the chapter where we focus on Group migration, I test the idea that the evolution of group formation in ecological contexts other than migration may facilitate the evolution of migration in groups. In the other chapter where the focus is on Long-distance migration, we are trying to understand the plausible evolutionary trade-offs between the costs of elaborated traits and costs of long-distance journey. Before carrying out these two sets of comparative analyses, I have also carried out simulations to test for the efficiency of the phylogenetic method that I use in my study. I will briefly discuss the results of those simulations and will focus mainly on the work on group migration in this presentation.