You were right, it’s not the same species as the other eggs. So if it’s not a dragon, what is it?

Ornithostoma is working on an offshoot of a dumpsite. He plans to finish eating it in about 13 years, give or take a few, but it's difficult to estimate when exactly he'll eat it all since people can put more things in it. He can breathe in the gases the heap produces for hours without becoming ill and spends much of his time "grazing", able to eat literally everything there. This is part of an operation by his friends, some smart dragons and humans, who are working on ways to reduce the amount of stuff in the town's dump. They especially want to limit toxic things and things that don't really break down, like broken contraptions and cursed books, and they use methods Ornithostoma is too young to understand. His job is to eat the dumpsite's "complicated" materials, which he does so with zeal.