We've had him for about 9 years. We are sure he's a male cockatiel so I'm sure it's not because he's in the process of laying an egg. We also have a younger cockatiel and he's pooping normally. They are eating the same thing so I don't think it's the food or water. Why do you think he's pooping like that? It's smelly and bigger (runnier?) than usual. If it's not normal, how can we help his poop get back to normal?

k

The question isn't why its poop is smelly its supposed to smell. The real question is why have you been smelling it poop? diarrhea maybe?

Many posible reasons , Illness, parasite , blockage,
Please , for your birds good health , See a vet

Raised many birds and have 7 parrots now
Icarus - Fischer Lovebird, Ruby-Fischer Lovebird, Charles Dickens-Quaker Parrot, Linus-Green Cheek Conure, Giggles-Peach face Lovebird, the twins-Fischers Lovebirds