19 July 2016
Cuckoos pay the cost of migratory short-cut
Population decline in the Common Cuckoo is linked to choice of migratory route, suggests a study in Nature Communications. The paper finds that migratory cuckoos that choose a shorter route in their migratory journey across the Sahara desert have higher mortality rates than those flying across longer distances.
The Common Cuckoo is a nest-parasitic bird declining in certain breeding populations across the UK. It has been unclear why some populations are declining at greater rates than others.
A new study, conducted in collaboration with researchers from Center for Macroecology, Climate and Evolution at the University of Copenhagen, found that birds from declining breeding populations are more likely to migrate to winter breeding grounds in central Africa along a Western route (via Spain) than along an Eastern route (via Italy and the Balkans).
The reseachers recorded a higher mortality along the shorter, western route and showed that this higher mortality occurred prior to reaching the Sahara desert, suggesting that birds may have encountered challenging drought conditions in Spain.
These findings, published in Nature Communications, demonstrate that routes taken during migrations can influence population success at breeding sites. Considering how conditions at stopover sites contribute to mortality during migration is critical to predicting future success of the cuckoo and other migratory birds, the authors suggest.
In the study, lead by the British Trust for Ornithology, the researchers used geolocators to track 42 male Common Cuckoos from the rapidly declining UK population during 56 autumn migrations in 2011-2014. They monitored the birds mortality during migration.
Associate Professor Kasper Thorup
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