The Fulvous Whistling-Duck is a pretty duck, very similar in shape to the Black-bellied Whistling-Duck, to the point that it can be confused with a Juvenile of the Black-bellied. I was lucky because three individuals came to swim on the lake by Concasa, so I spotted them when I returned home in the afternoon. This was unexpected, because I already knew that they only inhabit the northwestern region of Costa Rica, and should be not be found in the Central Valley. I took out my camera and snapped lots of pictures, because I assumed the birds would leave next day. And so they did, in the days afterwards there was no sight of them. Since then, a single individual has returned a few times joining a flock of Black-bellied, which seems pretty unusual. I have seen the Black-bellied pecking at this Fulvous, seemingly trying to drive it away, but it stays with the flock.
The Black-bellied Whistling-Duck is found in flocks taking residence around small ponds and lakes, becoming accustomed to people and relatively approachable. At dusk, they usually flock to the air, making circular trajectories and a lot of noise, and finally descending again into their watery home. Their calls are very high pitched and loud. Their necks are very flexible, so when resting, they normally turn their heads back and tuck they into the middle of their wings; they also like to stand up in one foot, with the other one hidden inside their belly feathers. Their bills are characteristically pink, as well as their legs. Juveniles are duller and have brownish bills instead. The Fulvous Whistling-Duck belongs to the same family and is very similar in shape, but has a different plumage coloration and gray bill and legs.