If birds left tracks in the sky, what would they look like ... “In winter the starlings gather in large groups,” says Bou, who took this photo in the agrarian village of Arbeca, Spain.

The research found the impressions were the first known fossil tracks of birds and lizards at the monument ... rounded hoofprints that may have come from a large herbivore such as an ancient ...

On the fourth try, the bird may have found something. Or perhaps it missed again and moved on. This glimpse into prehistory is possible thanks to two tiny fossil footprints and the dogged work of ...