Bird ichnology

In practice, the details of shape that reveal the birds' behavior or biologic affinity are generally given more weight in ichnologic classification.

Towards the end of the Cretaceous, the tracks of aquatic birds are usually recognizable due to the presence of webbing between the toes; indeed, most avian ichnotaxa fall into this group.

[1] There exist documented tracks that appear avian since the Late Triassic, by some 55 million years predating the first proper evidence that very birdlike theropods were present.

Few scientists would go as far though to consider these traces evidence that birds evolved much earlier than generally believed, and perhaps not from theropod dinosaurs as per today's mainstream opinion.

As they preserve direct evidence of an organism's physiology, their shape, size and the structure of the eggshell give more robust clues to their origin than do footprints.

Typically, fossil eggs can be quite unequivocally assigned to a specific group of organisms, e.g. chelonians, squamates, dinosaurs, crocodiles, pterosaurs or (modern) birds.

Male common teal producing feeding traces on a River Tyne mudflat .
Bird footprints typically have a wider angle between the toes. These goose tracks show that webs do not necessarily leave an impression.
Grallator are the footprints of a Coelophysis -like theropod , initially mistaken for those of a ratite bird.
Footprints of a large moa found in 1911
48-million-year-old bird and mammal footprints from the Early Eocene Green River Formation