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Abstract

In the northern hemisphere, songbirds disappear and reappear at certain 3mes of the year as part of their remarkable migra3on cycles. These migra3on cycles can encompass journeys of thousands of kilometers as North European songbirds make their way to the African con3nent to escape harsh winters. We know that songbirds inherit their migratory instruc3ons such as the 3ming, distance, and direc3on of migra3on from their parents yet the iden3ty of the gene3c and molecular components that are involved remains elusive. This thesis presents an integrated study into addressing this open ques3on. My thesis begins with two introductory chapters which review previous work on avian migratory biology. The first chapter reviews the behavioral ecology of migra3on, the physiological and behavioral adapta3ons that migratory birds have evolved, and research into the evolu3on and gene3cs of migratory behavior in birds. In chapter two of my thesis, I extend on chapter one with a literature review on the naviga3on mechanisms in the animal kingdom with a heavy focus on the naviga3onal mechanisms of migratory songbirds. Chapters three, four and five present experimental work dedicated to understanding the gene3cs and molecular architecture underlying migratory behavior in birds, using the Eurasian Blackcap (Sylvia Atricapilla). In chapter three I use RNA-sequencing to characterize the gene expression profiles of three brain regions likely involved with regula3ng migratory behavior in birds; the hippocampus, a region of the hypothalamus and cluster N, a brain region thought to process magne3c compass informa3on to gain insight into the region-specific molecular specialisa3ons of these brain regions. In chapter four, I compare changes in gene expression specifically related to the migratory phenotype in the three aforemen3oned brain regions to develop our understanding of how migra3on is regulated in songbirds. Finally, in chapter five, we u3lise resequencing data collected from blackcaps across their breeding range to reconstruct the evolu3onary history of the blackcap through demographic analyses and we scan the genome for variants associated with differences in migratory behavior. Through both the popula3on genomics and gene expression approaches, we provide novel insights into the molecular architecture underpinning migratory behavior in birds and iden3fy novel candidate genes and pathways which may be important in regula3ng this extraordinary phenotype.