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Sirirí pampa
Dendrocygna viduata  Two structural characteristics of sievers can be identified in the bill of this White-faced Whistling-Duck. A flared maxilla at the tip and a highly developed nail. Sievers feed separating food particles from the water. The lamellae, thin plates which line the edges of the bill, function like a strainer. They let water out and retain material food. © José Luis Merlo |