Linking events through the annual cycle in migratory songbirds: causes and consequences of different spatiotemporal strategies

Martins BRIEDIS

Doctoral thesis

Linking events through the annual cycle of small songbirds: the importance of carry-over effects for the ecology of migratory birds

Abstract:

Each year animals move across and between continents to track seasonal changes in resource availability and abundance to improve their survival and reproductive opportunities. Birds represent one of the largest animal group that engage in these global-scale migration events. Afro-Palearctic bird migration system is estimated to facilitate more than 2 billion individual birds that link ecological communities of the two continents. Recent advances in tracking technology, like light-level geolocators, have enabled us to follow even the smallest of individual migrants as they complete their annual cross-continental journeys. This has opened a new era in bird migration research allowing us to gain unique insights into spatiotemporal organization of full annual cycles of individual songbirds. Furthermore, these technological advances allow for estimation of migratory connectivity between breeding and non-breeding populations as well as linking spatially and temporarily distinct phases of the annual cycles of migratory birds. In my dissertation I couple geolocator tracking with stable isotope signatures, breeding data, and environmental variables to unravel spatiotemporal migration strategies and identify the importance of carry-over effects operating in wild populations of long-distance migrants. I reveal how annual events are interlinked with one another and the environment on the level of individual birds, populations, and species. I use three Afro-Palearctic migratory birds Tawny Pipit Anthus campestris, Collared Flycatcher Ficedula albicollis, and Semi-collared Flycatcher F. semitorquata as model species. Besides answering trivial questions of where and when each of the model species migrate, I found that there is a great deal of variation in the migration strategies among individuals and populations. Breeding site phenology is the main driver of migratory schedules on a population level, while individual variation in timing of migratory episodes are mediated via carry-over effects of previous breeding effort and conditions experienced at the non-breeding sites. Crossing of the Sahara Desert, which majority of the successful migrants accomplish in a single endurance flight, serves as a gateway between Europe and Africa for long-distance migratory birds. Only after the cross-desert flight, environmental and phenological cues can be picked up and used for accurate timing of spring migration and timely arrival for breeding. Studies from the perspective of full annual cycles are still underrepresented in animal ecology research. The chapters comprising this dissertation adds only a drop in the vast pool of knowledge in animal migration ecology. However, such information is of topmost priority for understanding the drivers of population dynamics as many migratory species are currently declining.

Abstract:

Each year animals move across and between continents to track seasonal changes in resource availability and abundance to improve their survival and reproductive opportunities. Birds represent one of the largest animal group that engage in these global-scale migration events. Afro-Palearctic bird migration system is estimated to facilitate more than 2 billion individual birds that link ecological communities of the two continents. Recent advances in tracking technology, like light-level geolocators, have enabled us to follow even the smallest of individual migrants as they complete their annual cross-continental journeys. This has opened a new era in bird migration research allowing us to gain unique insights into spatiotemporal organization of full annual cycles of individual songbirds. Furthermore, these technological advances allow for estimation of migratory connectivity between breeding and non-breeding populations as well as linking spatially and temporarily distinct phases of the annual cycles of migratory birds. In my dissertation I couple geolocator tracking with stable isotope signatures, breeding data, and environmental variables to unravel spatiotemporal migration strategies and identify the importance of carry-over effects operating in wild populations of long-distance migrants. I reveal how annual events are interlinked with one another and the environment on the level of individual birds, populations, and species. I use three Afro-Palearctic migratory birds Tawny Pipit Anthus campestris, Collared Flycatcher Ficedula albicollis, and Semi-collared Flycatcher F. semitorquata as model species. Besides answering trivial questions of where and when each of the model species migrate, I found that there is a great deal of variation in the migration strategies among individuals and populations. Breeding site phenology is the main driver of migratory schedules on a population level, while individual variation in timing of migratory episodes are mediated via carry-over effects of previous breeding effort and conditions experienced at the non-breeding sites. Crossing of the Sahara Desert, which majority of the successful migrants accomplish in a single endurance flight, serves as a gateway between Europe and Africa for long-distance migratory birds. Only after the cross-desert flight, environmental and phenological cues can be picked up and used for accurate timing of spring migration and timely arrival for breeding. Studies from the perspective of full annual cycles are still underrepresented in animal ecology research. The chapters comprising this dissertation adds only a drop in the vast pool of knowledge in animal migration ecology. However, such information is of topmost priority for understanding the drivers of population dynamics as many migratory species are currently declining.

Keywords

long-distance migrant, migration strategy, annual cycle, carry-over effects, migratory connectivity

Language used: English

Date on which the thesis was submitted / produced: 15. 7. 2017

Thesis defence

• Date of defence: 29. 8. 2017
• Supervisor: Mgr. Peter Adamík, Ph.D.

PALACKÝ UNIVERSITY OLOMOUC

Faculty of Science

Doctoral programme / field:
Biology / Zoology