Brood parasite. Growing up of a Common Cuckoo (Cuculus canorus) chick in the nest of Marsh Warbler (Acrocephalus palustris). Cuckoo's baby push out a marsh warbler chick from its nest.
Birds are genetically programmed to care for any chick in their nest. Whether it's there or not. The female cuckoo takes full advantage of that and lays her egg in the nest.
Yep, you saw that right. The parent birds eat the fecal sacs of the offspring. Disgusting, I know, but I heard that the smell of the fecal sacs might attract predators, so I think it’s one of the reasons why they do this. But, think of it as a bird’s way of changing diapers. LOL
What I don't understand is why the marsh warbler doesn't notice and carriers on feeding the interloper? The marsh warbler surely should kill the cuckoo chick or turf it out of it's nest? Why not? Bizarre.
I know this is a bit of a late response but - evolution has placed most of the emphasis on prevention for these birds. There’s too much risk in getting rid of chicks that have taken time and energy to hatch on the chance that it might be a cuckoo. They are roughly the same size as the normal chick when they hatch, so there’s not a clear difference until the parents have put in too much time for it to really matter in terms of being able to try again. Evolution-wise, it ended up being safer to raise any chick in the nest no matter what, but they will still destroy cuckoo eggs if they figure it out in time.
For all those wondering why the parent doesn’t kick out the cuckoo once the difference is obvious - birds don’t work like that. From what I understand (I could be wrong): once a chick hatches, the parents will raise it - they are evolutionarily incapable of recognizing any difference. This is because cuckoo chicks and regular chicks often aren’t that different looking when they’ve just hatched, and often it’s just the cuckoo so there’s nothing to compare it too. If parents were wired to have an ‘ideal’ chick in their heads to measure their own against, then there’s a good chance any slight difference would result in the deaths of their own offspring. And that’s not a great long-term plan for species survival. Over the course of evolution, it was evidently safer for these birds to try and prevent cuckoos from laying, and try to destroy cuckoo eggs, rather than somehow judge (they are BIRDS) what chicks do and do not qualify to be raised. TLDR; it’s better to take the L rather than accidentally kill your own kids because you think they’re a parasite and then be wrong because you’re a literal bird and you eat bugs and you can’t be bothered to judge that kind of thing. Also, sometimes birds will, in fact, kill cuckoo chicks. I don’t know either. Maybe they just felt like it.
Such a marvel! With all due respect to other point of views, for one time I wish I had the ability to comprehend Mother Warbler's language directly to hear why she still chose to raise the baby cuckoo? Perhaps this is an example of beyond bounds and frontiers...
The cuckoo parents will watch a nest to make sure the chick is cared for. If it dies they destroy the host birds nest. Thus the birds actually have a better chance of passing on their genes if they just accept whatever is in the nest. Its basically a mafia protection racket for birds. Thus the warbler is evolutionarily programmed to be loving and accepting of anything.
Many people hate cuckoos, and many other infamous bird species (some of which are completely unjustified if you ask me). But as harsh as this might be, it's part of nature, those cuckoos are trying to survive as well. And I think they are actually beautiful looking. You've got to think for each nest that's taken over by a cuckoo, many others will bloom
