International Research Fellowship Program: New World Bird Migration: Fast in the North, Slow in the South?

Jahn Alex E, Gainesville FL

Investigators

Abstract

The International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad. This award will support an eighteen-month research fellowship by Dr. Alex Jahn to work with Dr. Victor R. Cueto at the University of Buenos Aires in Argentina. Although bird migration has been the subject of substantial scientific study for decades, there is still surprisingly little known about the mechanisms driving bird migration at a global scale. A major reason for this is that most research on bird migration has been conducted in the Northern Hemisphere. How does bird migration in the Southern Hemisphere compare to migration in the Northern Hemisphere? Because the ultimate goal of spring migration is to successfully arrive on the breeding grounds to reproduce, the reproductive strategies of migrants could influence the strategies they use to get to the breeding grounds. North temperate breeding birds typically lay more eggs but have lower adult survival than south temperate breeders. Furthermore, food availability at north temperate latitudes is generally more predictable between years compared to south temperate latitudes. As a result, compared to south temperate breeders, migrants to north temperate breeding grounds should expect a greater reproductive payoff if they arrive on the breeding grounds in a timely manner. North temperate breeders should therefore migrate faster and possibly take more risks on migration than migrants headed to south temperate breeding grounds. The genus Tyrannus represents an ideal group with which to test this prediction because several species in this genus migrate to North American breeding grounds, while others migrate to South American breeding grounds. On each continent, these species are outfitted with geolocators, which allow researchers to track their movements throughout the year, permitting an evaluation of migration speed and migration routes. Their reproductive success is also studied on both continents to compare their reproductive strategies to their migratory strategies. This project not only offers a more complete picture of the mechanisms driving New World bird migration, it also opens new avenues to research on such pressing questions as: How does climate change affect birds in the Northern vs. Southern hemispheres? What time of year represents the major bottleneck to survival for migratory birds in each hemisphere? And, could adaptations for migration (e.g., navigation by stars, physiological endurance, cues to time migration) be different for species in each hemisphere?