Global warming is changing the migration pattern of billions of birds, forcing them to migrate earlier every spring, found a first-of-its-kind study released on Tuesday.

As a result of the rising temperature, the migrating birds are also passing certain stops earlier than they would have 20 years ago. The greatest change in the migration is happening in regions witnessing significant temperature rise.

According to researchers from Colorado State University and the University of Massachusetts Amherst, the response of birds to rapid and extreme changes in the climate has been a mystery for a long time.

"To see changes in timing at continental scales is truly impressive, especially considering the diversity of behaviors and strategies used by the many species the radars capture," Kyle Horton, lead researcher of the study said.

The observed shifts in the migration pattern do not necessarily mean that migrants are keeping pace with climate change, he added.

In order to understand the impact of climate change on nocturnal migratory birds, researchers analyzed 24 years of radar data from the National Oceanic and Atmospheric Administration (NOAA).

The analysis revealed that in the spring months, birds were migrating at a relatively rapid pace to reach the breeding grounds. "However, during the fall, there's not as much pressure to reach the wintering grounds, and migration tends to move at a slower, more punctuated pace," said Horton.

The study titled "Phenology of nocturnal avian migration has shifted at the continental scale" published in the journal Nature Climate Change also found that because of climate change, the timing of blooming vegetation or emergence of insects may be out of sync with the passage of migratory birds.

"These subtle shifts could have negative consequences for the health of migratory birds," said the study. The migration of birds is crucial for the ecosystem as they control the insect population and dispersal of seeds.