STOPOVER ECOLOGY AND CONSERVATION OF MIGRATORY LANDBIRDS IN NORTH AMERICA

Abstract

Migratory landbirds breeding in North America have experienced a steep population decline over the past five decades. Such decline is despite considerable conservation efforts directed toward the breeding grounds, and increasingly to the wintering grounds of most species in Central and South America. However, the migration period has been missing in most conservation efforts, mainly due to the lack of information about en-route habitat requirements and migration patterns at the population level. My dissertation aims to fill this gap in our knowledge of stopover ecology of migratory landbirds. In Chapters 1 and 2, I used weather radar to identify “stopover hotspots” and important habitats for migratory landbirds across the eastern United States. Chapter 1 confirms landbirds migrate across a broad front at the coarse scale, but highlights the presence of stopover hotspots that consistently support high densities of birds at finer scales. I also found evidence that the Midwest Corn Belt poses an inland migration barrier. Chapter 2 reveals substantial seasonal differences in stopover hotspots between spring and autumn migration, and the lack of protection for most stopover hotspots identified. Chapters 3 and 4 further explore how landbirds negotiate migration barriers. Chapter 3 shows that landbirds fly faster and select for better tailwind support when crossing the Corn Belt, which is a weaker barrier compared to crossing the Gulf of Mexico. In Chapter 4, I classified species-specific flight strategies for migration barriers using data from eBird and my field surveys. Most species fly nonstop across the Gulf in spring, but intermittently around the Gulf in autumn. In contrast, most species fly intermittently through the Corn Belt in both seasons, using forest fragments within the barrier as stopover sites. Species with more elongated wings are more likely to fly nonstop across both barriers. Overall, this dissertation contributes to the conservation of migratory landbirds in North America by highlighting stopover sites as conservation priority areas and revealing how birds negotiate different migration barriers.