When it comes to reproduction
Ducks are a remarkable family of birds (the Anatidae). They swim, they dive, they fly, their young are adorable and the males, known as drakes can be exceptionally pretty. Last but not least, expertly prepared they taste exceptionally good and that is one reason, why duck shooters are out to bag them. And that is also the reason why the New Zealand Duck Shooters’ Association had supported my student Dale Towers with a grant to study acceptability and design of nesting boxes by New Zealand Blue Ducks. Few people who accuse hunters and anglers of being cruel to animals seem not to know that people like duck shooters, hunters and anglers are usually excellent conservationists, who care and make sure that the animals they love (to shoot or hook) will still be around in the future. And come to think of it, what is more acceptable: to hunt and shoot an animal, which during its evolution got used to being attacked by predators? Or to befriend an animal, make it trust its owner, and then send it to the slaughterhouse?
Anyway, Dr Towers, noticed several things: experienced older ducks arrive early and choose their nest box in the centre of a cluster of boxes; that’s the safest place. Younger less experienced individuals have to make do with nest boxes at the periphery, where attacks by predators are more likely and the effects of bad weather, for example, strong wind can be more severe. He also noticed that the ducks frequently visit nest boxes that are not their own and quickly deposit an egg in another duck’s nest, if they find it unoccupied. Dale found that out of 10 eggs in a nest there could have been as many as six that were not laid by the nest owner, but by a different individual. And yet, these “other eggs” were not recognized or at least they were not removed, but brooded by the nest owner irrespective of the eggs’ origin that it was incubating. Did the nest owner not notice whose eggs she was sitting on or did it not matter at all?
Laying eggs into different nests can benefit the layer in several ways: The ‘brood parasite’ may not have found a suitable nest itself or should it experience a failed clutch of its own eggs, then having some of its eggs brooded elsewhere, the effort of laying the eggs was not wasted and offspring with the egg layer’s genetic material will be generated after all. It also means, of course, that ducklings from one clutch are not all brothers and sisters, but genetically mixed. That could perhaps prevent inbreeding. There is, however, a problem for the duck that sneaks in to lay an egg into the nest of another duck: it takes a bit of time and while the ‘brood parasite’ lays its egg in somebody else’s nest, it cannot guard its own nest and thus may herself be “parasitized” by another individual. Real cuckoo birds, of course, never have a nest of their own and invariably must choose a host for their own egg. However, while in the case of ducklings no fights ensue between the unequal siblings, in the cuckoo’s case the fate of its unrelated nestmates is sealed: they’ll be pushed out of the nest to die or may even be eaten by the young cuckoo.
What I really like about this blog’s title, is its tongue-in-cheek double meaning: yes, the female duck does behave like a cuckoo, when she lays her eggs in another nest, but the owner of the nest, also a duck, is “a real cuckoo” not to notice that she’s not sitting on only her own eggs, but brooding those of another individual (in English the word cuckoo is often used to mean “a stupid individual”).
© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2020.
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