ALTON, IL (KMOX) - You may have to look a little harder to find eagles in the area this winter as both milder temperatures and a reduction in their food supply have made the popular attraction sparser.

World Bird Sanctuary Director Jeffery Meshach says that as the freeze line has moved north in recent years, eagles haven’t had to come as far south to find open water and thawed carcasses.

But Meshach says a bigger concern is the loss of their primary prey, the gizzard shad, which is disappearing. That’s due at least in part to the introduction of an exotic carp species into local waterways.

“They don’t go out of their way to find the adult shad but they filter feed so I’m sure they eat all of the eggs that these shad produce and year after year after year as that’s happening, making the shad disappear from the river,” Meshach said.

Meshach says the number of eagles counted along the Mississippi between Quincy and Alton has dropped by more than half since reaching a peak of over 2100 in 2006.

“We haven’t had a count of a thousand eagles in that 134 miles of river in probably three years now,” Meshach said. “One of the reasons why is because it’s been so warm, we’ve had such mild winters.”