Evidence of colonial nesting and ‘site fidelity’ among ornithischian dinosaurs

Abstract

Recent discoveries in the late Cretaceous (Campanian) Two Medicine Formation of western Montana indicate that some dinosaur species, like some modern species of birds and crocodiles, nested in colonies. I report here evidence that members of one species returned to the same nesting area for many years. There are also indications that, after hatching, some species remained in their respective nests whereas others left the nest but remained in, or at least returned occasionally to, the nesting site. The area in which these discoveries were made is the Willow Creek Anticline of Teton County, where in 1978 a nest of fifteen, 1-m long hadrosaurs provided the first evidence of extended parental care among dinosaurs¹.