Cuckoo tricks to beat the neighborhood watch

Aug 02, 2012
Common cuckoo. Image: Wikipedia.

To minimise the chance of being recognised and thus attacked by the birds they are trying to parasitize, female cuckoos have evolved different guises. The new research, funded by the Natural Environment Research Council, was published today in the journal Science.

The common cuckoo (Cuculus canorus) lays its eggs in the nests of other birds. On hatching, the young cuckoo ejects the host's eggs and chicks from the nest, so the hosts end up raising a cuckoo chick rather than a of their own. To fight back, (a common host across Europe) have a first line of defence: they attack, or 'mob', the female cuckoo, which reduces the chance that their nest is parasitized.

Some female common cuckoos are grey and hawk-like, and previous research has shown that their resemblance to reduces host bird attack. However, other females are bright rufous (brownish-red). The presence of alternate colour morphs in the same species is rare in birds, but frequent among the females of parasitic cuckoo species. The new research shows that this is another cuckoo trick: cuckoos combat reed warbler mobbing by coming in different guises.

Cuckoos are secretive. To widen their source of information about local cuckoo activity, reed warblers eavesdrop on the mobbing behaviour of their neighbours. In the study, the researchers manipulated local frequencies of the more common grey colour cuckoo and the less common (in the United Kingdom) rufous colour cuckoo by placing models of the birds at neighbouring nests. They then recorded how the experience of watching neighbours mob changed responses back at their own nest.

They found that reed warblers increased their mobbing, but only to the cuckoo morph that their had mobbed. Therefore, as one cuckoo morph increases in frequency, local host populations will become alerted specifically to that morph. This means the alternate morph will be more likely to slip past host defences and lay undetected. This is the first time that 'social learning' has been documented in the evolution of mimicry as well as the evolution of different observable characteristics - such as colour - in the same species (called polymorphism).

Dr Rose Thorogood, of the University of Cambridge and co-author on the paper, said: "When mimetic disguises become less effective, evolving a polymorphism can be a successful trick. Our research shows that individuals assess disguises not only from personal experience, but also by observing others. However, because their learning is so specific, this social learning then selects for alternative cuckoo disguises and the arms race continues."

Professor Nick Davies, of the University of Cambridge and co-author on the paper, added: "It's well known that cuckoos have evolved various egg types which mimic those of their hosts in order to combat rejection. This research shows that cuckoos have also evolved alternate female morphs to sneak through the hosts' defences. This explains why many species which use mimicry, such as the , evolve different guises."

Explore further: Aging white lion euthanized at Ohio zoo

More information: 'Cuckoos combat socially transmitted defences of reed warbler hosts with a plumage polymorphism,' Science, 2012.

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User comments : 11

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wwqq
not rated yet Aug 02, 2012
It's interesting that they can learn what a cuckoo looks like, but not what a f-ing huge cuckoo chick(often larger than its adoptive parents) looks like.

Even if the cuckoo chick destroys one brood, if no cuckoos are raised they will eventually die out, solving the problem forever.
Telekinetic
not rated yet Aug 02, 2012
Employing disguises by the cuckoo constitutes "tool" use. Criminals will cause a distraction with a loud cohort while a more bland-looking gang member slips through unnoticed.
antialias_physorg
5 / 5 (1) Aug 03, 2012
Employing disguises by the cuckoo constitutes "tool" use.

This is not tool use as there is no tool. (Otherwise you would have to classify using your arms as 'tool use' which would lead the whole point of defining what tool use is ad absurdum)
Telekinetic
not rated yet Aug 03, 2012
From an English dictionary:
5.
anything used as a means of accomplishing a task or purpose: Education is a tool for success.

Any disguise, i.e., moustache, camouflage, change of accent or birdsong, as a means for subterfuge is a tool- and I may be able to apply the same term for you, antialias.
antialias_physorg
not rated yet Aug 03, 2012
A tool is something that is not part of you but which you use.
By your definition your voice can be 'a tool for communication', your hair can be a 'tool for keeping warm', a fin or a foot would be a 'tool for moving' ...anything and everything would be a tool by that definition (which renders the word completely meaningless)

If we use that we could state:
Planets have mass which causes gravitational attraction. Therefore planets are tool users because they use mass to cause gravity.
See how that doesn't really make sense?
From an English dictionary:
5.

Maybe you should also read 1-4. They state it quite plainly.
Telekinetic
not rated yet Aug 03, 2012
If I remember correctly, English is not your native language. There are idiomatic uses of words that may escape you.
The fact that a cuckoo can recognize an opportune time to lay her eggs while another cuckoo has caused a diversion requires the use of an action analogous to tool use, as in "she uses the distraction as a tool" to surreptitiously lay her eggs in another's nest.
Telekinetic
not rated yet Aug 03, 2012
Other birds will drop a mollusk on top of a rock formation to open the shell, which is using both gravity and the rocks below as "tools", yet neither gravity or an immobile rock formation would be considered a tool in your lexicon.
antialias_physorg
not rated yet Aug 03, 2012
If I remember correctly, English is not your native language. There are idiomatic uses of words that may escape you.

I probably have a better command of the language than you do (because I learned to speak it AND learned to understand its structure)
And I am well aware of the notion of 'tool use' as it pertains to biological/behavioral studies - and your 'definition' doesn't fit it.
That you find something in an urban dictionary doesn't mean that that is the way it's used in science. It's just being obtuse.

which is using both gravity and the rocks below as "tools", yet neither gravity or an immobile rock formation would be considered a tool in your lexicon.

Gravity is not. The rock is. It is an external, consciously chosen implement to accomplish a task. (Gravity is also 'external', but it is not consciously chosen as it it's present everywhere)
Telekinetic
not rated yet Aug 03, 2012


"I probably have a better command of the language than you do"- antialias

"Draught years with low water levels will only exacerbate the problem (ha, finally found a sentence to use THAT word in)."-antialias June 4, 2012

"Drought" years must have been your intention, but draught beer for cooling is a thought when in Bavaria."-Telekinetic June 4th, 2012

You were saying?...

Telekinetic
not rated yet Aug 03, 2012
"Drought" years must have been your intention"- Telekinetic June 4, 2012
"Well, well...you live and you learn."-antialias June 4, 2012

I remembered our exchange while tooling down the highway!
antialias_physorg
not rated yet Aug 04, 2012
Yep a typo due to autocorrect. You found one. Congratulations. you must be massively proud of yourself for that. I think we should really erect a statue to you.

By the way...when you said (and I don't even have to go to another thread but just up a few posts):
yet neither gravity or an immobile rock formation would be considered a tool in your lexicon.

You probably meant dictionary - not lexicon. A lexicon is a list of words. A dictionary contains the definitions.
(But I suppose that lexicon isn't 'english enough' for you as it's a word with a greek origin)

...but all of this makes your point about the misuse of the word 'tool'...exactly how?

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