NEW YORK— A new study finds that the death toll for birds that crash into buildings may be underestimated by hundreds of millions and could exceed 1 billion deaths a year.

The peer-reviewed study, published in PLOS One journal, noted that previous research only accounted for birds found dead or fatally wounded at the scene of the collision, with injured or stunned birds assumed to survive long-term. But researchers have now found that about 60% of injured birds ended up dying in veterinarian care after a collision.

“This heartbreaking study drives home how much more the Fish and Wildlife Service must do to truly protect vulnerable birds from window collisions,” said Tara Zuardo, a senior campaigner at the Center for Biological Diversity. “This is a national problem that requires national action. It’s time for federal officials to step up to protect our birds.”

The study may push federal officials to finally confront a problem that claims more than 1 billion birds a year. Even as some cities have passed window collision-prevention policies, the U.S. Fish and Wildlife Service has failed to act.

North America’s bird populations have plunged by almost 3 billion birds over the past five decades, according a landmark study — a loss of nearly one in four birds since 1970.

“Fish and Wildlife Service officials have the power to regulate and fine those who cause the death of migrating birds, and they should use it to protect our country’s declining bird populations,” said Zuardo. “Unsafe buildings are absolutely deadly for birds, and it’s time to crack down on this threat.”