Reserva Ecológica Costanera Sur

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

Infanticide

"As we were walking along the Lizard Path Gaby told me: "Look how fast this ducklingis moving", I take a photo and there comes a female Rosy-billed Pochard, takes it from the head, shakes it leaving it badly hurt. The female swims away and a minute later she comes back and again takes it from the head and this time kills the duckling. Once she finished she came back with her four ducklings. As this was taking place there was another female Rosy-billed Pochard protecting her own ducklings at the edge of the pond. We do not know whether the female Pochard killed it because it was his own or it belonged to another family or another species. Everybody was quite shocked to see this event."
Pato picazo/Rosy-billed Pochard9 12 16 © Amelia Besana

Pato picazo/Rosy-billed Pochard9 12 16 © Pablo Fernández

Pato picazo/Rosy-billed Pochard9 12 16 © Amelia Besana

9 12 16 © Amelia Besana

9 12 16 © Amelia Besana

Pato picazo/Rosy-billed Pochard9 12 16 © Amelia Besana


This is the first case of a duckling killed by a conspecific. If it is not nice to see a duckling being attacked by a raptor though we understand it as survival, this seems unimaginable. Nevertheless, these infanticidal cases are much more commonly reported on the internet. In most cases killings are carried out by males.
Infanticide is the killing of a young by a same-species adult (conspecific). If th adult is the parent then it is a filicide. There is another type of killing to which youngs are exposed - that caused by a brother in which case is called fratricide. This practice is common among young which stay in the nest and are fed by the parents. Where there is scarcity of food the bigger ends up killing the rest. Herons are a good example and have been thoroughly studied.
In this case the doer is not a male but a female. But it is not so striking since in this species it is the female alone which is in charge of the ducklings. The male disppears from the scene. The victim is Rosy-billed Pochard duckling. I believe it is bigger than the ducklings of the perpetrator. So it is not her own.

Why this infanticidal behaviour? Though it may seem brutal to us the infanticidal behaviour may be an adaptive behaviour. There are several hypothesis to explain this fact and they refer to two main causes: one survival (lack of food, or breeding sites, or space); the other one, genetic hegemony (not to adopt unrelated young or get rid of a clutch to have one's own).
Of all these hypothesis some may be discarded right away. Space might be a matter of discussion. Though the pond is very bing and there seem to be few birds, it is also true that there is not enough free space to stand on. And families with their young need to keep distance one from the other. At this moment there are too many Rosy-billed Pochards in the pond. They outnumber all the other species together. If room is the cause, we would probably have more casualties.
It could also be that the female wanted to avoid the adoption of an unrelated young. As we have already had cases of parasitism by Fulvous Whislting-Duck (See cases) this would lead us to think that female Rosy-bille Pochards only recognize what is born in the clutch. A posteriori they reject latecomers.

Unluckily the story had already begun when they discovered the duckling and photographed it. But its plumage shows that it has already been sunk. From the story there were at least three attacks separated by a time interval. May be the victim got desoriented, mixed with this family and had a tragic end. The duckling might belong to the family at the edge, but we do not know that.

On two other occasions I witnessed critical situations involving young, but no with this sad ending. The lost cygnet and the orphan dukclings. In the coscoroba cygnet the adult moved this cygnet away from his own and deserted it. The second case is an interspecies case. The parents of a Ringed Teal family choose to abandon a group of orphan Rosy-billed Pochards.