The Palo Verde National Park in the Guanacaste province of Costa Rica is a crucial water source for birds during the dry season. The Tampisque River floods the marshlands, creating both fresh and saltwater habitats. The floodplain hosts many species including these Black-bellied Whistling Ducks, which congregate by the thousands in noisy flocks. Here, a few ducks fly over the marshland and surrounding hillside at sunset.