More than four million birds crossed Illinois Saturday night into Sunday morning and more are expected in the coming days as an annual spring migration of birds over the United States continues.
According to Birdcast, an average of 11.2 million birds were in flight during the overnight hours since Saturday.
That trend is expected to continue Monday and Tuesday night, with officials expecting “high levels” of migrating birds to take flight over the state. You can find a bird migration map here.
“You may observe their movements birding and listening by day and night,” an alert from Birdcast said. “Remember that high intensity nocturnal migration may not necessarily mean an excellent day of birding; rather it means that large numbers of birds are migrating or predicted to migrate at night.”
Each year, thousands of birds are killed during migrations when they strike buildings and power lines, with experts urging the public to take steps to protect their health and safety.
Officials advised residents to protect the nocturnally migrating birds by turning off non-essential lighting from 11:00PM Monday until 6:00AM Tuesday morning.
“Every spring and fall, billions of birds migrate through the US, mostly under the cover of darkness,” Birdwatch said. “This mass movement of birds must contend with a dramatically increasing but still largely unrecognized threat: light pollution.”
Residents were also asked to leave cats indoors, as the animals tend to be more active at night as they hunt for prey.
During the spring migration, an estimated 313 million birds have crossed over Illinois as they journey north to Wisconsin and into Canada, Birdcast said. The birds will often make stops in Illinois on that journey, providing dazzling shows for birdwatchers across the state.
Several species of warblers, including the Yellow Warbler and Nashville Warbler, are migrating through Illinois on their way northward, along with Baltimore Orioles and several other species, according to Birdcast.