Four‑Chambered Hearts: Birds Share This Mammalian Trait

Birds possess a fully four‑chambered heart (two atria, two ventricles) with complete separation of systemic and pulmonary circulations—just like mammals. This enables high‑pressure, high‑output delivery essential for flight metabolism. Crocodilians also have four chambers but with a unique shunt (foramen of Panizza) allowing partial mixing.