MOAB — Human inhabitants would later name this spot in Utah's high desert the Cedar Mountain Formation. But picture it on a day millions of years ago:

The area is warm and humid, perhaps like Louisiana now. There is a lake, 50 feet deep in the middle and shallow at the shoreline. Lightweight birds feed in the inches-deep water, leaving tracks that will be preserved intact for 125 million years — and which on Tuesday were called the oldest bird tracks ever found on the North American continent.

Utah's state paleontologist, Dr. James Kirkland, said at the site in the desert mountains near Moab that the tracks "date at the same age as one of the most important discoveries of this century in terms of dinosaurs and birds," a time of change among the earth's creatures.

John Foster, curator of paleontology at the Museum of Western Colorado, agreed. "To get much older than this, you have to go into the late Jurassic and the (bird) bones that have been discovered in Europe."

Joanna Wright from the University of Colorado, Denver, said it's hard to say exactly what kind of feathered creatures made the tracks. "They were small, perhaps the size of shoreline birds we see along the Great Salt Lake," she said. "But we couldn't put them in a family of modern birds because they go back too far."

Foster said the birds are probably descendants of creatures that began emerging from dinosaurs some 20 million years earlier.

"So what we're seeing here are birds that are already on the branch that split off from carnivorous dinosaurs — and they're already starting to specialize in what they do." he said.

Kirkland, Utah State Geological Survey paleontologist Don DeBlieux and Dinosaur National Monument paleontologist Scott Madsen were all on hand Tuesday, gathering more data on the discovery at what is called the Yellow Cat Member of the Cedar Mountain Formation.

Some rappelled from the top of the mesa down a 400-foot cliff to document the age of the layer where the tracks were found.

Along with bird tracks, the Colorado and Utah scientists are uncovering even more from what Kirkland calls "a gold mine for earth scientists — a whole new realm for discoveries of dinosaurs, birds and other creatures."

The Cedar Mountain Formation is like layer after layer of a set of prehistoric diaries. Sandwiched in these layers, the Cretaceous Period is several hundred feet thick. There's a couple of miles of Jurassic Period, when dinosaurs were dominant, below that, and a couple of miles of Late Cretaceous on top.