The Swainson’s Thrush (Catharus ustulatus) is a long-distance migratory bird whose annual journey across the Americas is closely linked to seasonal changes in vegetation. Using monthly NDVI data (January–December), this study shows how the species follows areas of high vegetation productivity throughout the year. During January–February, Swainson’s Thrushes remain in the green tropical forests of South America, where food is abundant.
As NDVI increases across Central America in March–April, the birds begin their northward migration, tracking newly growing vegetation. Peak NDVI in May–June across Canada and Alaska supports breeding by providing high insect availability. When vegetation declines in July–August, the birds prepare for migration by storing energy. In September–October, they move south through forested corridors and productive stopover habitats. By November–December, rising NDVI in the Amazon signals a return to wintering grounds. This simple NDVI-based visualization highlights how seasonal vegetation dynamics guide migration routes and demonstrates the value of remote sensing for understanding and conserving migratory birds.
