From evolutionary point of view, the most important goal in life is reproducing. Getting your genes in the next generation. After you did this, you can lay back, relax and die happily (which is what some species, such as salmon, actually do). But reproduction can be hassle, especially when you are a duck. First, you have to find a suitable mate. Then you have to lay the eggs, incubate them and take care of the little chicks that crawl out of them. I already get tired just writing about this whole process.
Some duck species have found a way to circumvent this laborious procedure. They just lay their eggs in the nest of another female in the hope that she will raise the dubious ducklings. In general, eggs are laid in the nests of conspecifics, but some birds also target the nests of other species. This behavior – known as heterospecific brood parasitism (or HBP) – was the focus of a recent study in Wildfowl. In South Bohemia (Czech Republic), Petr Musil and his colleagues noted down the proportion of HBP in five different duck species:
- Gadwall (Anas strepera)
- Mallard (Anas platyrhynchos)
- Red-crested Pochard (Netta rufina)
- Common Pochard (Aythya ferina)
- Tufted Duck (Aythya fuligula)
Their analysis revealed that the highest proportion of brood parasitism occurred among Red-crested Pochard, while Tufted Duck showed the lowest proportion.
The study did not look into hybridization, but it is feasible that HBP can lead to hybrids. When the ducklings crawl out of the egg, they can get imprinted on their mother. If, for example, a Mallard duckling hatches in a Red-crested Pochard nest, that duckling might grow up thinking it is a Red-crested Pochard (talk about an identity crisis!). Later on, this bird might look for a partner of the latter species, resulting in hybridization. I have described this process in my review paper on goose hybrids:
Hybridization between the species studied by Petr Musil and his colleagues is quite common. Indeed, the top five of most common hybrids in Central Europe includes four crosses among these species (Randler 2008). Here is the list (happy to see my beloved geese grabbing the bronze!):
- Common Pochard x Tufted Duck (838 records)
- Common Pochard x Ferruginous Duck (332 records)
- Greylag Goose x Canada Goose (283 records)
- Ferruginous Duck x Tufted Duck (94 records)
- Mallard x Red-crested Pochard (73 records)
It would be interesting to compare the number of hybrids with the proportion of HBP in Czech Republic…
Musil, P, Z Musilová, K Poláková. (2017) Facultative heterospecific brood parasitism among the clutches and broods of duck species breeding in South Bohemia, Czech Republic. Wildfowl 67:113-122.
Ottenburghs, J, P van Hooft, SE van Wieren, RC Ydenberg, HHT Prins. (2016) Hybridization in geese: a review. Frontiers in Zoology 13:1-9.
Randler, C. (2008) Hybrid wildfowl in Central Europe – an overview. Waterbirds 31:143-146.