Carol Gilsenan

Variation in Settlement and Breeding Patterns in the Blue Tit Cyanistes caeruleus
"Settlement" refers to the time period where an individual disperses from a natal site or previous breeding site, establishes a new nest site, and forms a pair bond with a new mate (or reunites with a previous mate). Many studies investigating the breeding biology of passerines have quantified "breeding success" in individuals by only comparing the fitness differences of breeding individuals in a population. However, another essential element in understanding breeding success in birds comes from studying differences between individuals which have bred and individuals which have not managed to get the opportunity to breed. This means that some of the most important selection processes for who actually gets to breed in a particular year are probably occurring during settlement. My project aims to investigate variation in nest site choice and pair formation during the settlement period, as well as inter-individual interactions such as competition for nestbox resources. I am mainly interested in differences in settlement patterns:

• between individuals which settle in nestboxes in different areas and at different times
• between individuals which settle in nestboxes and breed versus individuals which exhibit territory settlement behaviour by visiting nestboxes but end up not breeding that year
• within individuals settling in the area over multiple breeding seasons
• at the pair level, brought about by temporal differences in pair formation

I also intend to explore how settlement patterns are influenced by ecological factors such as microhabitat quality or predation risk. I am also interested in the process and fitness consequences of divorce in birds, and intend to compare breeding parameters and reproductive success in faithful pairs and pairs which contain divorcé(e)s. For all of these studies, I will use a population of wild blue tits (Cyanistes caeruleus) at our field site in southern Germany.