To invest or not to invest: Uncovering parental investment strategies in the Common Swift

For animals rearing offspring it is crucial to optimally divide resources among current offspring and future offspring and consequently their own body condition. This is especially true for long living species which reproduce multiple times during their lives. The Common Swift (Apus apus) is a suitable organism to investigate parental investment in the context of life history strategies because this long-lived species has an exceptional lifestyle and produces offspring annually. The Common Swift is a long-distance migratory bird and highly aerial. Due to a long developmental period of the young in combination with a restricted diet (exclusively aeroplankton) it is facing challenging conditions during breeding season. Variation in breeding success of pairs breeding under similar conditions might be an indication of varying parental investment strategies. We have the great opportunity to investigate the breeding behavior of the Common Swift in a breeding colony near Olpe, Germany and generate long-term data about the life history of individuals. By measuring the investment from “egg to fledge” of different individuals in consecutive years we can discover changes in investment strategies and determine factors influencing such strategies. Here I will present an overview of our research questions and methods used to investigate and uncover variation within and between individuals. I will further present preliminary results on the variation of maternal investment in eggs of the Common Swift.