Were dinosaurs social animals?

Some dinosaurs were social creatures. Lately discovered evidence indicates that they travelled together and that some may even have migrated (because dinosaur fossils have been establish above the Arctic Circle, where food provide would have been seasonal). Grouped hadrosaur nest sites have been found with poorly crushed eggshells and skeletons of baby dinosaurs (with slightly worn teeth) still in the nests, signifying that some babies stayed in their nests after hatching and possibly were fed by parents.