- Neartic-Neotropical migrants (Eastern Kingbird, T. tyrannus; Western Kingbird, T. verticalis; and Scissor-tailed Flycatcher, T. forficatus). These species reproduce at north-temperate latitudes and spend the winter in the tropics. Our study sites during the breeding season are located in New York, Nebraska, Oklahoma and Oregon. In winter, we study one of these species (Eastern Kingbird) in Bolivia.
- Neotropical austral migrants (Fork-tailed Flycatcher, T. savana, and Tropical Kingbird, T. melancholicus). These species reproduce at south-temperate latitudes of South America and spend the winter in the tropics of South America (primarily in the Amazon and Orinoco River basins). Our study sites during the breeding season are in Argentina. During winter, we study these species in Colombia and Venezuela.
- Intra-tropical migrants (Fork-tailed Flycatcher, Tropical Kingbird, and White-throated Kingbird, T. albogularis). These species have populations that migrate wholly within the tropics (primarily the Amazon River basin). We study these populations during the breeding season in Bolivia and Brazil.