New research from our Biosciences Department and the British Trust for Ornithology (BTO) has revealed that many migratory birds are finding it harder to prepare for their long journeys as European summers become hotter.
These changes could threaten their ability to complete the thousands of kilometres they travel each year between Africa and Europe.
Climate change challenges long-distance travellers
Migratory birds rely on building up body fat known as a 'migratory fuel load' before setting off on their journeys.
This fuel allows them to cross difficult areas such as the Mediterranean Sea and the Sahara Desert without stopping to feed.
However, scientists have discovered that these birds are now struggling to build up enough reserves, particularly after warmer summers.
Four decades of change
The research team studied 33 species of Afro-Palearctic migratory birds using long-term data from 286 sites across Europe, collected over the last 40 years.
The results show a clear decline in the birds' ability to gain sufficient weight before migration.
In addition, the timing of when birds begin to store energy has changed, with those in northern Europe starting earlier, and those in southern areas starting later than before.
These shifts are linked to changing weather patterns and food availability caused by rising temperatures and increased drought. Such conditions reduce the amount and quality of food that birds depend on to prepare for migration.
A warning for the future
Researchers say the findings highlight how climate change is affecting even the most resilient wildlife.
They warn that unless these trends are addressed, many migratory bird populations could continue to decline, reducing biodiversity across Europe and beyond.
