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It's not stupidity that leads birds to raise cuckoos eggs it's the fact that cuckoos are mobsters who check up after laying and if their egg/chick isn't still there they destroy the entire nest and clutch of eggs.

The other species live with the parasitism grudgingly not obliviously!

I thought that at least in some species the brood parasite evicts the other young from the nest-- in this case there would be no reason to not abandon it if it truly were detected.

The cuckoo actually does this: https://www.youtube.com/watch?v=SO1WccH2_YM. What I still don't understand is why the paristized birds—here the Reed Warbler—continue to feed the cuckoo chick when it's not in its evolutionary best interest.

Surely Reed Warblers know the chick is not their own so what's going on?

The only logic I can come up with is that there's a symbiotic relationship between cuckoos and birds that it paristizes that's evolved over millions of years which is that the cuckoo acts as a population control agent. In effect it regulates the population of birds in the area of bushland it covers and thus ensures that there is enough food, territory to nest etc. for all birds in the area.

If it's not something like that then the Reed Warbler must be dumb. If neither of those ideas fit then what else could it be?

(Look at it this way, the Reed Warbler pair has committed huge resources in building a nest and brooding three eggs. All that is effectively destroyed by the cuckoo so why would a 'sensible' Reed Warbler continue to feed the cuckoo chick?)

> why would a 'sensible' Reed Warbler continue to feed the cuckoo chick

Same reason humans raise step kids. Assumed Parental obligations.

Probably so, but perhaps we should research it more to know for certain. If this is inate behavior across the much of the animal kingdom then it becomes a fact with useful potential.

Eh. I can't see the potential usefulness of that information at least not enough to warrant research.

By and by I suppose.

Since posting that and other earlier comments I've read up on this matter and particularly on brood parasites both on Wiki and elsewhere and I'm much better informed now (see these debates are actually useful). :-)

The short and overly simplified explanation is that a considerable amount of research has been done over many years and it's deemed useful for various reasons, understanding species longevity, rates of extinction, the evolutionary one-upmanship between the parasites and those who stand to lose by being parasitized and so on. What is clear is that there are many quite logical and reasonable theories about said matters but little actual proof so more research is needed before any definitive conclusions are drawn.

At least on the matter of brood parasites this wiki is a good place to start as it provides a reasonably comprehensive overview (other sites are more specific and some I've only skimmed so I'm not in the position to comment about them): https://en.m.wikipedia.org/wiki/Brood_parasite.

One thing for certain is that these matters are complex and often there are multiple-threaded explanations (that is different explanations can simultaneously apply to each case without conflict).

Maybe cuckoos do this to breed birds for their acceptance of cuckoos eggs, which might help birds learning to accept them.

OK, that makes sense whilst the clutch of eggs remain in the nest but once the cuckoo chick has ejected them there is no reason for the birds to continue nesting there.

As I said to nullc there has to be some other reason why, say, the Reed Warbler continues to feed a cuckoo chick twice its size with now no viable offspring of its own if it's not oblivious to the fact (see video in that post).

> I may be wrong but I simply cannot image that a bird with the inate intelligence of this currawong would let itself be a surrogate for raising a cuckoo's young.

I imagine birds raise cuckoos not because they think they are their offspring, but because of some instinctive imperative like we mammals have for raising any kind of puppy.

if memory serves in many cases ( because there are a lot of parasite birds ) it's an evolutionary thing to prevent the parasite layer from destroying their own eggs - many of the parasite species will check on the nest after the fact and destroy it / the eggs if their eggs have been removed

OK, presumably 'parasite' birds instinctively know the various species of birds that they can get away with the practice. Laying an egg in an osprey or eagle's nest would likely mean they'd end up as food.

Is there any definitive research on this?

Yeah! They tend to specialize against particular species!

I don't have research documents on hand atm, but I do have a terrifying video about them from zefrank: https://youtu.be/9TZQDA2yabg

Sorry I didn't reply earlier when I first read post but then I only skimmed the video. Since seen it thoroughly several times and I am surprised at the extent of this parasitic action by birds, I knew vaguely about the cuckoo but not much else about the subject.

I think I've learned more from that story on 'Bin chickens than any other HN story in quite a while, it took me down all sorts of alleys, research papers, etc.

Initially I wasn't even going to click on this story as there are so many of them on HN and I've only a casual interest in birds from the fact that I see then in my neighborhood. It's interesting really how things turn out (and how one learns things).

Exactly. A bird isn't "raising young" in an abstract way. It has genes that produce certain behaviour. Build nest. Sit on egg. Roll egg out of nest if you get too hungry. Regurgitate food into squaking red mouth. Remove feces from nest. Taken together you get some level of success in reproduction.

And expecting a bird to be "intelligent" in this situation would imply a source of knowledge about what an egg is supposed to look like.

That makes sense, as I said above (after reading these posts) it seems to amount to how one defines intelligence. What you are referring to is survival/evolutionary intelligence which is inate/built-in and expressed though a bird's genes. What I was referring to was the cognitive intelligence (ability to learn from circumstance and experience and act upon it as covids and currawongs do over and above their inate/instinctive behavior).

I should have been more perceptive and not mixed these. This begs the question that I've posed elsewhere: the cuckoo and other parasitic birds would, I'd reckon, also act out of inate gene-based expression in that they'd have to be quite selective about which species of birds they lay their eggs in (as I said, if they were to lay eggs in an osprey or eagle's nest then they'd likely be food).

Any info on this?

Well, you got chickens and then you got corvids - and that's your avian intelligence scale, from 0 to 1.

Chickens are the dumbest animal on earth. They're dumber than fish. They're dumber than oysters. They're even dumber than people. They only survive because they breed so much and because we breed so many of them to eat them.

You are what you eat, we say. We eat so much chicken that we've become dumb like them and an animal that does something that a chicken would never do, on account of the animal not being terminally dumb as the chicken, strikes us as really clever. Hey, look at that clever bird, it learned to eat the toads. Yeah, duh. People used to come up with tricks like that all the time, back in the day, when they had to find their food in the wild. Nowadays the greatest challenge in securing sustenance is in finding which aisle the pasta was moved to every time the supermarket hires a new manager.

Intelligence is so overrated. What does it all lead to in the end? We've dominated our environment and now our environment sucks, and btw, it's also dying, with us in it. All those smarts that helped us eat wild animals and poisonous plants, they don't look that smart now, do they?

But maybe those birds, those "bin chickens", are really smart. They've learned to live in our world, even after we've covered up everything with concrete and cars. Maybe when we're gone they'll evolve into a better intelligent species than ours, make a better civilisation than ours. One that is not so smart that it can't avoid destroying itself.

i would put turkeys below chickens. the ones we had could not even find there way out of an open pen.

"They're even dumber than people. "

Years ago when thinking about this I used to envisage a graph with a log scale that would indicate the intelligence of brightest humans (the Einsteins of this world), the dumbest ones and also all other supposedly sentient animals extending way down to the simplest forms of life.

I pictured the graph with humans way out in front at the top but closely grouped together (that is there isn't that much difference between the dumbest and smartest human on an absolute scale). The next most intelligent animal on the scale would be widely separated from humans and a long way down the graph (despite the log scale).

In recent years, witnessing some of the things you mention and other antics I've seen, that gap has just about eroded altogether. Now, I no longer have any clear idea where humans should be placed on the graph (I still find it hard to believe how stupid humans can be—and I'm not being elitist about it as I include myself in that category).

Right, we need to reevaluate intelligence, IQ tests don't mean much in the grand schema. I suppose the thing that may distinguish us humans from other species is that at least some of us know how stupid we humans are.

BTW, I'd still group all humans pretty much together on an absolute scale (if it were ever possible to construct one), we're all pretty much the same.

PS: you're right about chickens, they're about as dumb as it gets when intelligence is measured in cognitive terms, but as you infer surviving with humans implies evolutionary intelligence (again what is intelligence?). Nevertheless, the difference in intelligence (in its cognitive sense) between chickens and covids and currawongs are miles apart—a comparison would almost be a non sequitur.

Not directly answering your question but related: Pepperberg and colleagues have done a fair amount of research into quantifying avian intelligence. There is a film called Life With Alex about her work with a Congo African Grey that is pretty interesting.

Noted, thanks.

I’m sorry to have to let you know that the pied currawong is in fact parasitised by the channel billed cuckoo (the world’s biggest cuckoo in fact).

That's ingesting to know. What about the black currawong (they're the only species I've experience of)?

You may also wish to answer the question I've asked elsewhere, which is the cuckoo's inate behavior must also extend to the species it selects as surrogate hosts for its young (would it risk laying an egg in an eagle's nest at the risk of becoming food?).

...Much later.

I've since done a little research on this and now have a somewhat clearer understanding of brood parasites and I've learned that it's no simple matter. However, one thing is apparent and that's despite there being many quite logical theories about it there's no clear proof about why the parasites and those being parasitized act the way they do—see my comment to vagrantJin.

> would let itself be a surrogate for raising a cuckoo's young.

I don't find it surprising at all. Imagine a mother from the earliest humans, not equipped with complex language, formal education, or a civilization-- gives birth. Somehow an infant chimp is slipped into her lap along with her own baby.

Both babies look weird, one is strangely hairless one is strangely harry. Both cling on and nurse. Seems obvious to me that mom is going to try to tend to both babies.

And a chimp isn't evolved to be a human brood parasite. If it were it would be more similar to humans in whatever ways mattered to the instincts and perceptions of the host (but not necessarily look very similar to a third party species).

So if you could at least imagine this working on a primitive human, then it's not at all surprising that it works on some birds.

In some sense you could see that capacity for raising a foreign young as itself a sign of intelligence: A highly unintelligent species would only raise its young in ways triggered by an extremely narrow and exact set of signals, while a more intelligent species may be more able to accommodate the differences and figure out how to make things work even when they're not quite right.

Think of all the scams modern humans fall for that can be warded off by "hey, watch out for scams that look like xyz". In both the birds case and the early pre-language human case, no one could have warned them that they might be exploited by impersonator babies.

Why on earth are you feeding a currawong? They’re among the meanest most mercenary omnivores; they hardly need your help.

The pied variant looks 100% like the thing New Zealanders call a magpie.

Vicious and horrible.

First, one can't explain all fine details in a post or it'd be too long and wouldn't be read so I'll expand the post here.

It may surprise you but from my limited experience I agree with you that currawongs are about the meanest most mercenary omnivore I've seen. I suppose I've had a casual interest in them from early on, when as child of about five one attacked me whilst I was walking with my mother in a park. It dive-bombed me and its beak left my head bleeding.

I never feed them regularly but only when it suits me such as when I'm eating or have scraps immediately to hand and it's only when I've time. The reason is that the birds and one in particular will come very close to me where I can study their behavior in response to things I do such as moving around, staring at them and so on. From this it's clear to me that currawongs are significantly more intelligent than say pidgins or seagulls (having observed them in similar situations) and on a spectrum I'd put the ibis somewhere between them and currawongs but closer to the latter. It's their intelligence that holds my interest.

Feeding currawongs means that I can be within a meter or so of them for quite some minutes. What I found intriguing is how quickly they learn and remember and they do so for a long time. As I said, they know me and others in the neighborhood, they have no difficulty in distinguishing between people and they show this by responding very differently to each person they've become aware of. I can be away for weeks and sometimes several months can pass between my interactions with them yet they still specifically remember me from others.

Outside domesticated pets, they are essentially the only animal I've had regular interaction with that has sufficient cognition and intelligence to single me out from others and remember the fact. That alone makes them fascinating from an observational perspective (essentially it's curiosity that drives my interaction with them).

Note: I'm not an expert in animal behavior nor do I have anything other than a general interest in the subject (I've a technology-based background).