11-21-2025

Billions of birds depend on the 'Five Great Forests' that are now vanishing

BySanjana Gajbhiye

Earth.com staff writer

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Spring returns with familiar notes. Birds fill parks with sound after months away. People enjoy the noise, but few know where the long trip begins. The story starts deep in Central America, inside forests that shape the lives of birds across two continents.

A new study from the Wildlife Conservation Society (WCS) and the Cornell Lab of Ornithology shows how strongly birds rely on the Five Great Forests of Central America.

These forests stretch from southern Mexico into northern Colombia. Many species spend most of the year there, not in North America.

Birds and the Five Great Forests

Researchers used eBird information to track weekly movements. Millions of observations revealed clear patterns across seasons.

The Five Great Forests support between one-tenth and almost one=half of global populations for forty migratory species.

“What happens in Central America directly affects the birds we love in the United States and Canada,” said lead author Anna Lello Smith from the Wildlife Conservation Society.

“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.”

Where the birds live

Kentucky Warblers gather in these forests in huge numbers. Wood Thrushes and Golden-winged Warblers follow the same pattern. Cerulean Warblers rely on the forests even more, with over 40 percent passing through during spring migration.

Two regions hold especially high concentrations. The Selva Maya and the Moskitia stand out in the study. Both regions lost a quarter of their area in only 15 years. Illegal cattle ranching fueled most of that loss.

This cluster of forests covers an area the size of Virginia. Jaguars move through it. Scarlet Macaws nest within it. Tapirs roam its rivers. Migratory birds stop here to recover before moving north.

“Every fall, billions of birds pour south through the narrow land bridge of Central America,” said study co-author Viviana Ruiz-Gutierrez, director of Conservation Science at the Cornell Lab of Ornithology.

“The density of migratory warblers, flycatchers, and vireos crowded into these five forests is astounding.”

Five Great Forests are disappearing

Large areas continue to disappear. Deforestation has already cleared millions of acres. The Moskitia alone lost almost one-third of its cover in 20 years. That loss puts pressure on many species that define spring across eastern North America.

“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.

Radachowsky believes that support for rural communities and conservation partners can still slow the decline.

Community efforts drive protection

Local and Indigenous groups rebuild damaged land. They repair fire lines and grow crops like cacao and allspice without harming wildlife.

This local work protects habitats that migratory birds need to survive long journeys. Many face danger while defending these forests. Their work continues despite limited resources.

“Imagine the possibility of linking with those efforts,” said Ruiz Gutierrez. Her call highlights the need for cooperation across countries.

North-south forest connections

Researchers also mapped how these forests connect to northern breeding regions. The study followed a framework from Partners in Flight and the Cornell Lab.

The results reveal ties to the Appalachians, the Mississippi Delta, the Great Lakes, New England, and the area around New York City.

Scientists call these northern regions “sister landscapes.” The same species move between them each year.

A bird that sings in a summer forest in New England might rest in the Selva Maya months later. These connections show how actions in one region shape life in another.

Forests are bird lifelines

The Five Great Forests act as tropical counterparts to eastern North American forests. Scarlet Tanagers rest there. Golden-winged Warblers recover energy there. Broad-winged Hawks shelter there during winter.

The return of these species each spring depends on these southern places. Without them, the sound and color of spring would thin out across the north.

“Every hectare we protect in Central America has ripple effects for birds and people across the hemisphere,” said Lello Smith. Her message invites people to learn about the forests that support the birds they enjoy each year.

The path ahead remains open. Spring will keep its voice only if these forests endure. Birds cross thousands of miles.

Their survival hinges on the last large forests of Central America. Our experience each spring depends on those same places. Protecting these forests keeps that connection alive.