Tracking the movements of three species of migratory birds indicates that finding food may become a challenge for them by the end of the century.
A new paper in Science Advances shows that common cuckoos, red-backed shrikes, and thrush nightingales can closely follow the complex seasonal vegetation changes occurring within their non-breeding grounds in sub-Saharan Africa.
“We show that all three birds cross continents to match highest levels of resource supply,” explains Kasper Thorup, professor at the Center for Macroecology, Evolution and Climate, University of Copenhagen and first author of the study.
“The bird’s migration-program guides them to areas where food availability has been high in the past. So, what is interesting now is the bird’s ability to adjust their migration pattern to match future changes in food availability.”
In total, researchers tracked 38 individual birds to establish the migration routes. The common cuckoo was tracked using satellite tracking, while the smaller red-backed shrikes and trust nightingale were tracked using light loggers, Thorup explains.
“All three species have complex migration routes covering large parts of Europe and Africa with many stops along their way. Mapping their routes has only been possible using the newest available technology from satellite telemetry in cuckoos to small tags that log light-levels in red-backed shrikes and thrush nightingales.
The study shows that the migration pattern in cuckoos matched high levels of green vegetation whereas it matched local vegetation peaks for red-backed and nightingales. Both green vegetation and vegetation peaks are presumably related to abundant food availability.
The scientist compared the observed migration route to projections of food availability for 2080. This showed a mismatch between seasonal resources and the birds expected presence.
“We believe that bird’s innate program to guide them over long distances must be adapted to long-term average of food availability,” says coauthor Carsten Rahbek, professor at the Center for Macroecology, Evolution and Climate.
“Our results suggest that by the end of this century climate change, and other impacts on the food source, like land use changes, could negatively influence the birds’ chances to find sufficient food.”
Source: University of Copenhagen