The hoatzin (Opisthocomus hoazin), a tropical bird native to the Amazon and Orinoco basins, possesses an unusual digestive system. Unlike most birds, which rely on a muscular gizzard to grind seeds and insects, the hoatzin is a strict folivore, feeding almost exclusively on leaves. To digest this fibrous diet, the bird utilizes foregut fermentation, a process facilitated by a highly enlarged crop and lower esophagus. Specialized symbiotic bacteria in these organs break down cellulose before the food reaches the stomach. While this adaptation allows the hoatzin to extract nutrients from otherwise indigestible foliage, it has a significant trade-off: the heavy, filled crop restricts the development of the bird's breastbone and flight muscles, making the hoatzin a notoriously weak and clumsy flyer.
Based on the text, what is true of the hoatzin's digestive system?
- AIt relies on a highly developed muscular gizzard to process seeds and insects.
- It employs symbiotic bacteria to break down cellulose before food enters the stomach.Answer
- CIt prevents the bird from gaining enough nutrients from its diet of foliage.
- DIt is a common adaptation shared by most other bird species in the Amazon and Orinoco basins.