Dinosaur eggs have been found in many places all over the world. Eggs need to be protected since they make a good meal for any predator. They also need to be kept at a constant temperature to allow the embryo to develop properly.
Birds are warm-blooded and therefore have a constant temperature.
They usually sit on their eggs to incubate them. Crocodiles, however, tend to bury their eggs. They sometimes use rotting vegetation or volcanic heat to keep the eggs warm. There are actually some surprising clues to indicate that dinosaurs like Allosaurus buried their eggs. Near Lourinha, Portugal, a dinosaur nest has been found with tiny dinosaur embryos inside.