Connectivity between countries established by landbirds and raptors migrating along the African-Eurasian flyway

Osprey. Sarah Kelman / BTO

Author(s): Guilherme, J.L., Jones, V.R., Catry, I., Beal, M., Dias, M.P., Oppel, S., Vickery, J.A., Hewson, C.M., Butchart, S.H.M. & Rodrigues, A.S.L.

Published: September 2022  

Journal: Conservation Biology

Digital Identifier No. (DOI): 10.1111/cobi.14002

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The importance of the African-Eurasian flyway to long-distance migratory populations is well known, as are the many threats that the birds face on their journeys. Recent advances in tracking technology have provided vital information for conservation action, for example revealing the routes and stopover sites birds use, but work to address any threats identified has been hindered by fragmented and inaccessible datasets. Can bringing these studies into a single resource reveal new information that would enable more effective conservation action?

Each year, more than two billion birds migrate along the African-Eurasian flyway. The increasing availability of tracking technology, involving attaching very small devices to migrant songbirds, has provided greater insight into these movements and highlighted the diverse range of threats the birds face en route. Unfortunately, the results of these tracking studies are often stored in ways that are fragmented, inaccessible or subject to biases, making it challenging to apply them for conservation action.

This international study, involving BTO, addressed the problem by combining data from 132 studies, covering 43 species, into a comprehensive review of published African-Eurasian flyway migratory records. The researchers quantified the degree of linkage between breeding and wintering grounds, with the strength of each link dependent on the proportion of those individuals from a country’s breeding population that wintered in a particular country in Africa. Using this technique, the researchers identified how countries are linked through the process of migration, creating an opportunity to foster greater international cooperation and develop conservation policy in relevant regions.  

Data from 1,229 individual birds and 71 countries were included in the study. Importantly, however, the researchers found that published data were only available for a tiny fraction of the relevant species. This was particularly true for land birds, for which only 7.5% of the available species were, on average, tracked per country. Smaller-bodied birds and records from eastern European countries were also underrepresented. Despite this, the study provides some fascinating insights into intercontinental migration. It reports an extensive network of 544 migratory links, connecting the countries within Europe and Africa. Based on the available data, Sweden had the most migratory links for its breeding populations (63), while Spain featured the most individual species (14). In contrast, Mali was the most significant African country for both number of migratory links (47) and species (21). Although based on limited data, this exercise demonstrates that valuable findings can be uncovered when scientists collaborate to ensure data are freely available.  

The study revealed a number of interesting patterns. Land birds were found to rely more heavily on central and southern African countries compared to raptors, but the differences became even more apparent when examined at the species level. In some species (e.g. the Great Reed Warbler), a small number of individuals settled in many different African countries, while for others (e.g. Montagu’s Harrier), a substantial proportion of the European population travelled to a single location. Different populations of the same species also employed different strategies. For example, Finnish Ospreys travelled to diverse locations across Africa while, in contrast, 62% of their British counterparts were concentrated in just Senegal and The Gambia.

As the majority of migrant species could not be included because of the lack of data, the study greatly underestimates the number of migratory links that exist along the flyway. By identifying the most critical gaps in the dataset, this research provides direction and incentivises the collection of more targeted tracking data from locations which simultaneously increase coverage and prioritise key species (e.g. Cuckoo in Poland, Stone-curlew in Ethiopia). This study provides policymakers with a valuable tool, informing international conservation plans, and will undoubtedly facilitate conservation efforts along the flyway and improve the long-term prospects of many declining migratory species.


The conservation of long-distance migratory birds requires coordination between the multiple countries connected by the movements of these species. The recent expansion of tracking studies is shedding new light on these movements, but much of this information is fragmented and inaccessible to conservation practitioners and policy decision-makers. Here, we synthesize current knowledge on the connectivity established between countries by landbirds and raptors migrating along the African-Eurasian flyway. We reviewed tracking studies to compile migration records for 1,229 individual birds, from which we derived 544 migratory links, each link corresponding to a species’ connection between a breeding country in Europe and a non-breeding country in sub-Saharan Africa. We used these migratory links to analyse trends in knowledge over time, as well as spatial patterns of connectivity per country (across species), per species (across countries) and at the flyway scale (across all countries and all species). We found the taxonomic coverage of existing tracking data to be highly incomplete, with, to date, an average of just 7.5% of migratory landbird species and 14.6% of raptor species tracked per country. Furthermore, existing data are biased towards more westerly countries and larger bodied species. Despite these limitations, existing data can already inform conservation efforts, and we provide species- and country-level syntheses of the migratory links we identified (involving 123 populations of 43 species, migrating between 28 European and 43 African countries). Finally, we highlight countries (e.g., Spain, Poland, Ethiopia, Democratic Republic of Congo) that are strategic priorities for future tracking studies to complement existing data, particularly on landbirds. Our data and analyses can inform discussions under two key policy instruments at the flyway scale: the African-Eurasian Migratory Landbirds Action Plan, and the Memorandum of Understanding on the Conservation of Migratory Birds of Prey in Africa and Eurasia.


The authors thank all scientists, conservationists and enthusiasts for their persistence and long field hours involved in capturing and tracking the birds whose migration records we used to estimate migratory links, and all experts from EU Member States that contributed to the official reporting under Article 12 of the EU's Birds Directive (2013-2018) and those from European countries and territories outside the EU, who provided data for the European Red List of Birds 2021. This study has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 766417. IC was supported by Fundação para a Ciência e Tecnologia (FCT) contract DL57/2016/CP1440/CT0023.
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