Can moldy bread kill a cockatiel?

Yes, moldy bread can be harmful and potentially fatal to a cockatiel. Mold can produce mycotoxins, which are toxic compounds that can lead to serious health issues, including respiratory problems, liver damage, and even death. It's important to avoid feeding any moldy food to birds and to provide them with a balanced diet of fresh, safe foods. If a cockatiel has ingested moldy bread, it's advisable to consult a veterinarian immediately.