The pre-migratory flight behaviour in a songbird migrant – spatiotemporal characteristics and potential delayed fitness consequences

• Applicant: Professor Dr. Heiko Schmaljohann
• Subject Area: Ecology and Biodiversity of Animals and Ecosystems, Organismic Interactions
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 451271063

Bird migrants travel between their breeding areas and wintering grounds to make use of the seasonal fluctuation of resources in these environments. Birds’ specific annual cycle events, e.g., breeding and migrating, are chronologically well-adjusted and adapted to the ecosystems they inhabit. If birds deviate from this temporal pattern, they may experience unfavourable conditions, e.g., food shortage or harsh environments migration. These conditions may have immediate fitness consequences, i.e., temporal deviation directly causing death, and delayed fitness consequences, i.e., temporal deviation causing decreased reproductive success. Studying when birds deviate from the expected temporal pattern is important to recognize the causes(s) of the deviation and to predict the corresponding consequences. Most songbird migration studies have focused on how variation in the wintering ground affects later annual cycle events. Only a few studies investigated whether and how changes in the breeding area result in delayed fitness consequences. This is partly so because, the key features of the wintering grounds, i.e., location and habitat quality, can be identified by data loggers and remote sensing, but the key features of the breeding period, e.g., the timing of breeding, parental investment and preparation for migration, cannot. The latter represents the transition from the stationary breeding period to the mobile migratory period. During this transition, significant behavioural and physiological changes occur to prepare for migration. A study of migrant songbirds showed that birds flew around for several hours at night and then landed again in the breeding area. Four potential reasons for these “pre-migratory flights” are discussed: i) Practising nocturnal flights, ii) developing orientation skills, iii) generating a magnetic/landscape map and iv) practising evaluating meteorological conditions. Little is known about the spatiotemporal characteristic of these pre-migratory flights. We do not know if they influence the start of autumn migration and the return to the breeding area and thus have delayed fitness consequences. The genetic basis of the pre-migratory flights has not been studied. This research proposal will fill parts of these gaps. We will study the breeding population of northern wheatears (Oenanthe oenanthe) on Norderney. The combination of the array of radio receiving stations in the North Sea and radio-transmitters running for > 1 year would enable us to record the spatiotemporal characteristics of the pre-migratory flights, the start of autumn migration and subsequent breeding area arrival timing. The genetic basis of these behavioural traits will be studied with hand-raised northern wheatears from Norderney under laboratory conditions. The realization of this project would provide detailed knowledge about the pre-migratory flights under natural and laboratory conditions that are essential for a holistic understanding of bird migration.

• DFG Programme: Research Grants