Influence of experience and migratory distance on the variation of the realised and endogenous migration behaviour
Zusammenfassung der Projektergebnisse
Juvenile nocturnally migrating songbirds travel thousands of kilometres to their wintering areas without guidance of their parents or siblings. How to arrive at the population-specific wintering site and in time is told by their individual-specific innate migration program. This defines individual’s spatiotemporal organisation of migration and how to react to the changing environment. Tracking the first autumn migration at a high spatiotemporal resolution will show how the endogenously controlled migration program guides birds through space and time. In contrast to juveniles, adult birds have experience from former migratory journeys which may influence their organisation of migration. By comparing the realised migration of both groups, we can describe the genetic basis of migration and potentially assess whether movement ecology is age-specific due to experience/learning from former migrations. Because a longer migration distance has to be linked with greater migration time and higher energy costs of migration as well as less time for other life history traits, i.e., breeding, moult, wintering, stronger stabilizing selection pressure is thought to act on species/populations with longer migration routes. I, therefore, expect higher variation in specific migratory traits to be found in populations with short than with longer migration distances. The influence of experience and migratory distance on the variation of the realised and endogenous migration behaviour was supposed to be studied in a long-distance songbird migrant, the Northern Wheatear Oenanthe oenanthe. This species breeds circumpolar, but its winter distribution is restricted to sub-Sahelian Africa. Consequently, different breeding populations encounter quite different migration distances. This together with the fact that birds migrate independently of others makes the Northern Wheatear an ideal model species for the above named research topics. I intended to answer these questions by tagging juvenile and adult birds of different populations with lightlevel geolocators and tracking their corresponding migratory movements. Due to technical problems and extremely severe weather conditions during the field season, the sample size gained after two years of field work was unfortunately insufficient to find answers to these still major challenges in movement ecology. Nevertheless, data were appropriate to show that birds react to environmental parameters differently along their migration route. Here, I provide first direct evidence that stopover duration, departure probability and distance covered per night were spatial-specifically adjusted to environmental cues along the 15,000 km migration route by the Alaskan Northern Wheatears. Exploiting favourable flow assistance to accelerate their nocturnal flight range intensified in spring when approaching the breeding area. In autumn, nocturnal flight range increased with a drop in surface air temperature while being in the subarctic, likely to avoid high energy cost of thermoregulation on the ground. Later in the course of migration this effect of temperature on travel speed diminished. The study further shows that a change in stopover duration significantly affected birds’ total speed of migration, i.e. its phenology. These results demonstrate that future models need to integrate this concept of spatial-specific reaction norms to the environment to assess how human-induced changes in nature will affect migrants’ speed of migration and with that their phenologies in the future.
Projektbezogene Publikationen (Auswahl)
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2016. Proximate causes of avian protandry in a long-distance migrant: a comparison of subspecies with contrasting migration routes. Behavioral Ecology 27, 321-331
Schmaljohann, H., Meier, C., Arlt, D., Bairlein, F., van Oosten, H., Morbey, Y. E., Åkesson, S., Buchmann, M., Chernetsov, N., Desaever, R., Elliott, J., Hellström, M., Liechti, F., López, A., Middleton, J., Ottosson, U., Pärt, T., Spina, F. & Eikenaar, C.
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Common Terns on the East Atlantic Flyway: Temporal-spatial distribution during the non-breeding period. Journal of Ornithology, October 2016, Volume 157, Issue 4, pp 927–940
Becker, P.H., Schmaljohann, H., Riechert, J., Wagenknecht,G., Zajková, Z., González-Solís, J.
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Tracking the Stejneger’s stonechat Saxicola stejnegeri along the East Asian-Australian Flyway from Japan via China to Southeast Asia. Journal of Avian Biology. Vol 48 Issue 2, Febr 2017, Pages 197-202
Yamaura, Y., Schmaljohann, H., Lisovski, S., Senzaki, M., Kawamura, K., Fujimaki, Y. & Nakamura, F.
