Population declines and carry over effects in sub-Saharan migrant birds


Main supervisor: Prof Stuart Bearhop
Co-supervisor(s): Dr Malcolm Burgess (RSPB Centre for Conservation Science),Prof William O. C. Symondson (Cardiff University), (), (), ()

Project enquiries

Email: s.bearhop@exeter.ac.yk
Contact number: 01326 371835

Host institution: University of Exeter

CASE Partner: The Royal Society for the Protection of Birds

Project description

Long-distance migratory passerines that breed in Europe and winter in sub-Saharan Africa have seen substantial declines over the past 20 years, with many populations declining by more than 50%. For many species, work has almost exclusively focused within breeding grounds, which can fail to pinpoint causal mechanisms as it only considers part of the annual cycle. This is not surprising given our lack of knowledge about where many of these migrant species go in the non-breeding season. However, recent developments in tracking technology and forensics are set to revolutionise this field and it already seems likely that while these species are specialists during breeding, they are generalists during winter, using a range of habitats including areas of subsistence agriculture.

Among Neotropical migrants, winter habitat selection has been shown to be a key determinant of survival and fitness for a number of species, yet we have virtually no understanding of how such carry-over effects might influence the ecology of Afro-Palaearctic migrants. For example, although Pied flycatchers have been subject to decades of study on the UK breeding grounds, their populations have declined by 48% since 1995 and the causes remain largely unknown, suggesting the regulation is occurring during the non-breeding season.
This project will use miniaturised tracking technologies (the team has already tracked the three species of interest: Pied flycatcher, Wood Warbler and Spotted Flycatcher) and stable isotopic provenancing to investigate non-breeding season ecology. A multi-isotope approach will also allow us to infer habitat preferences (including intra-population differences and interspecific differences). The student will use study populations that have been set up by the CASE supervisor over the last 10 years in Devon, and ongoing studies of breeding ecology (including dietary studies and DNA barcoding) will form a key element of the project. There will also be an opportunity for African fieldwork to establish mechanistic links between habitat and fitness (locations based on previous tracking data).

The student will use these data (breeding ecology, phenology, winter ecology) to parameterise models of the annual cycles of each species in order to understand the key factors and periods that drive differences in fitness among individuals. S/he will also utilise remote sensing data (using RSPB expertise) to model habitat preferences in winter and how this has changed over time.

This is an exciting project providing the opportunity for the student to work with a leading conservation NGO and conduct fieldwork overseas, and use cutting edge technology and analytical approaches to study a topic of fundamental importance to conservation biology.


J. A. Vickery, S. R. Ewing, K. W. Smith, D. J. Pain, F. Bairlein, F et al. The decline of Afro-Palaearctic migrants and an assessment of potential causes. Ibis 156, 1 (2013)
X. A. Harrison, J. D. Blount, R. Inger, D. R. Norris, S. Bearhop. Carry-over effects as drivers of fitness differences in animals. Journal of Animal Ecology 80, 4 (2011)
P. P. Marra, K. A. Hobson, R. T. Holmes. Linking Winter and Summer Events in a Migratory Bird by Using Stable-Carbon Isotopes. Science 282, 1884 (1998)
A. A. Chabot, K. A. Hobson, S. L. Van Wilgenburg, G. J. McQuat, S. C. Lougheed, Advances in Linking Wintering Migrant Birds to Their Breeding-Ground Origins Using Combined Analyses of Genetic and Stable Isotope Markers. PLoS ONE 7, e43627 (2012)

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