Every spring, the familiar songs of Wood Thrushes and warblers return to parks and backyards across eastern North America. Their seasonal arrival feels local, yet these birds spend most of their lives much farther south, supported by the lush and often remote forests of Central America.

New Research Identifies Critical Forest Refuges

A new study from the Wildlife Conservation Society (WCS) and the Cornell Lab of Ornithology (Cornell Lab), published in Biological Conservation, reports that the Five Great Forests of Central America, which extend from southern Mexico to northern Colombia, are essential habitats for dozens of migratory bird species that connect the two continents.

Drawing on detailed weekly distribution data generated from millions of birdwatcher observations submitted to the Cornell Lab’s eBird platform, the research team found that these forests collectively hold between one-tenth and nearly one-half of the global populations of 40 migratory species. Many of these birds are among the fastest declining in North America.

“What happens in Central America directly affects the birds we love in the United States and Canada,” said Anna Lello-Smith, lead author and conservation scientist at WCS. “These forests aren’t just tropical wilderness—they’re at the heart of migration, sustaining many of our birds for more than half the year. They provide the food and shelter that allow Wood Thrushes, Magnolia Warblers, and so many others to return north to fill our spring with song and color.”

Key Findings on Bird Populations

More than one-third of the world’s Kentucky Warblers and nearly one-quarter of all Wood Thrushes and Golden-winged Warblers spend the winter within these forests.

Over 40 percent of the global Cerulean Warbler population, a species that has declined by more than 70 percent since 1970, passes through these forests during the spring migration period.

The Selva Maya (spanning Mexico, Belize, and Guatemala) and the Moskitia (in Honduras and Nicaragua) are the most vital regions for these species, but they are also the most threatened, having lost a quarter of their area in the past 15 years, mostly due to illegal cattle ranching.

A Living Bridge for Wildlife

Together, the Selva Maya, Moskitia, Indio Maíz-Tortuguero, La Amistad, and Darién create an ecological corridor roughly the size of Virginia. This vast region shelters migratory songbirds along with jaguars, scarlet macaws, tapirs, and many other species. For birds that travel thousands of miles each year, these forests function as irreplaceable winter habitats and resting points.

“Every fall, billions of birds pour south through the narrow land bridge of Central America,” said Viviana Ruiz-Gutierrez, director of Conservation Science at the Cornell Lab of Ornithology and co-author of the study. “The density of migratory warblers, flycatchers, and vireos crowded into these five forests is astounding, and means that each hectare protected there safeguards a disproportionate number of birds.”

Rapid Forest Loss Threatens Essential Habitat

These forests are disappearing at a rapid pace. Illegal cattle ranching has already destroyed millions of acres. In the Moskitia alone, almost one-third of the forest has been cleared in the past two decades.

“If we lose the last great forests of Central America—and we are—we lose the birds that define our eastern forests in North America,” said Jeremy Radachowsky, Regional Director for WCS’s Mesoamerica Program. “But by supporting rural communities, governments, and conservation partners on the ground, we can still turn the tide.”

Across Central America, Indigenous and local communities are working to restore degraded lands, battle forest fires, and maintain bird-friendly traditions such as sustainable cacao and allspice production. Many face real danger while protecting these landscapes, yet their efforts remain essential.

“Imagine the possibility of linking with those efforts,” said Ruiz-Gutierrez, “so that we can work together across the Americas to bring back our shared migratory birds.”

Connecting Bird Habitats Across the Hemisphere

In the past, cross-border conservation efforts struggled because scientists lacked a full picture of how birds move between regions throughout the year. To strengthen collaboration, the study used a framework created by Partners in Flight and the Cornell Lab to identify “stewardship connections”—areas of North America where species linked to the Five Great Forests gather to breed.

The research shows strong connections between the Five Great Forests and forested regions in the Appalachians, the Mississippi Delta, the Great Lakes, New England, and the landscapes surrounding New York City. Scientists refer to these paired regions as “sister landscapes” because they share the same species at different stages of the migratory cycle.

Protecting Forests to Sustain Migration

In many ways, the Five Great Forests act as tropical mirrors of North America’s eastern forests. They shelter the same community of forest-loving birds, including Scarlet Tanagers, Kentucky Warblers, Golden-winged Warblers, and Broad-winged Hawks, during the months when these species are far from their breeding territories. Safeguarding these wintering grounds and stopover points is essential to ensuring that migratory birds continue returning north each year.

“Every hectare we protect in Central America has ripple effects for birds and people across the hemisphere,” said Lello-Smith. “The forests that sustain thrushes and warblers also support communities. If you love watching your birds come back each spring, we invite you to discover the tropical forests they call home for most of the year—and help protect them.”