Projected changes in prevailing winds for transatlantic migratory birds under global warming

Area of Science:

• Ornithology
• Climate Science
• Ecology

Background:

• North American terrestrial birds migrate across the Atlantic to Caribbean/South American non-breeding grounds.
• Oceanic crossings by migratory birds are influenced by wind speed and direction, which are subject to change with global warming.
• The impact of changing wind patterns on transoceanic migratory bird populations remains largely unaddressed.

Purpose of the Study:

• To investigate the potential impacts of climate change on the autumn migration of 10 North American terrestrial bird species crossing the Atlantic.
• To analyze projected changes in wind patterns within the transatlantic flyway and their implications for migratory birds.

Main Methods:

• Utilized eBird occurrence data (1950-2015) to map daily population centers for 10 species.
• Estimated autumn migration timing and location within the transatlantic flyway.
• Analyzed projected wind speed anomalies (1996-2005 vs. 2091-2100) from 29 Coupled Model Intercomparison Project Phase 5 (CMIP5) models.

Main Results:

• Autumn transatlantic migrants face strong westerly crosswinds early in their journey, headwinds in the Caribbean, and weak tailwinds east of the Caribbean.
• CMIP5 simulations indicate a decrease in strong westerly crosswinds encountered by migrants this century.
• Climate change may reduce the need for compensatory flight strategies against crosswinds during the initial migration phase.

Conclusions:

• Climate change is projected to diminish strong westerly crosswinds, potentially easing the initial phase of autumn transatlantic bird migration.
• The findings suggest that existing strategies for avoiding headwinds and utilizing tailwinds will remain relevant.
• Reduced wind-related challenges could decrease energy expenditure, mortality, and vagrancy risk for these migratory bird species.