The Cockatrice egg is a "bonus" drop from a Cockatrice (level 37 combat), which makes it among regular drops from this creature. It is used in Herblore and Summoning.
- Herblore: used to create summoning potions.
- Summoning: used to create Spirit cockatrice pouches to summon Spirit cockatrices.
It can`t be incubated at a pet shop.
They can also be made from a normal chicken egg by using the Spirit cobra's scroll Ophidian Incubation.
Also note that having a Spirit Cockatrice familiar seems to boost the odds of getting the drop of a cockatrice egg while fighting against Cockatrices, and the Spirit Cockatrice will also create one every now and then.