Reserva Ecológica Costanera Sur

Sitio realizado por aficionados a la observación de aves desde 10 de enero 2006

Parasitism by Fulvous Whistling-Duck - Dendrocygna bicolor

The Fulvous Whistling-Duck may dump eggs in other birds' nests either of their same species (intraspecific) or other species (interspecific). To ascertain that a Fulvous Whistling duckling is an intruder is very difficult. All look alike. Either DNA studies or catching the parasitic female red-handed and all the eggs hatched are needed. Instead they make out easily when they accompany ducklings of another species.
The process of laying eggs in a host's nest to be incubated and after hatching to be raised is called parasitism. Fulvous Whistling-Ducks dump eggs occasionally, since they can also build nests and raise their ducklings. That is why this parasitism is known as facultative. Facultative parasitism is mostly found in anatids, where the process only requires incubation of the eggs since ducklings feed on their own.

At Costanera we have seen many Fulvous Whistling-Duck families grow. We do not know if they have been parasitized intraspecifically. But up to now (2016) we have had two cases of interspecific parasitism, being the host a Rosy-billed Pochard in the two cases.

Pato picazo/Rosy-billed Pochard20 12 09 © José Luis Merlo
The first case was registered by José Luis Merlo. This was a very peculiar time for the reserve as it was for the whole pampean area which had been affected by a servere drought in 2008. This was only a relief since en 2010 the ponds got dried again, the landscape changed completely and it was not until 2013 when works began to refill the ponds with water from the river. Might this case have been favoured by a scarcity of aquatic environment?

© Roberto Ares


Pato picazo/Rosy-billed Pochard25 2 15 © Claudia y Diego Bastías
The second family was spotted by Claudio y Diego Bastías with two Fulvous Whistling-Duck chicks
Picazo-sirirí/Pochard-Whistling-Duck8 3 15 © Diego Carús
Picazo-sirirí/Pochard-Whistling-Duck9 3 15 © Claudia y Diego Bastías
Picazo-S. colorado/Rosy-billed P-Fulvous W-D29 03 15 © Carlos González Ledo
Picazo-S. colorado/Rosy-billed P-Fulvous W-D8 04 15 © Claudia y Tito Di Mauro
Picazo-S. colorado/Rosy-billed P-Fulvous W-D8 04 15 © Claudia y Tito Di Mauro
The Fulvous Whistling-Duck is still with the Pochard family.