Scientists found fossilised depressions and footprints in Alaska's Denali National Park and Preserve in what is believed to be the first evidence of prehistoric wading birds probing for food, a geologist said on Friday.
The tracks and the feeding marks found in rocks formed from freshwater sediments were 65 million to 70 million years old, said Phil Brease, a geologist at Denali National Park.
Such evidence of prehistoric birds' feeding behaviour is difficult to find because the marks made in the mud disappear easily and the fossilised evidence often erodes, Brease said.
Geologists discovered the tracks and marks last summer, but confirmed the work over the winter after studying photographs and molds.
Denali National Park is an emerging hotbed of fossil findings. A team of geologists also discovered a fossilised footprint of a three-toed, meat-eating dinosaur known as a theropod.