Cuckoos and Instinct

[rynner2]

Today I heard R4's Open Country on Marsden Cuckoo Day. According to local legend

Many years ago the people of Marsden were aware that when the cuckoo arrived, so did the Spring and sunshine. They tried to keep Spring forever, by building a tower around the Cuckoo. Unfortunately, as the last stones were about to be laid, away flew the cuckoo. If only they'd built the tower one layer higher. As the legend says, it "were nobbut just wun course too low".

But I'm posting here because the cuckoo is a very strange bird, and our familiarity with it rather obscures this strangeness.

Cuckoos arrive in Britain in the spring from Africa, and the females lay their eggs in other birds nests (RSPB info ). The cuckoo egg is pre-incubated, so hatches first, and the hatchling then turfs out all the other eggs, so getting the undivided attention of its adopted parents.

Adult cuckoos return to Africa in August, but the young ones follow on a month later. (Which raises the big mystery of bird migration, in spades: not only how do the young cuckoos navigate, but how do they even know they are supposed to migrate, without older birds to guide them?)

And then there is the mystery of how adult cuckoos recognise each other in order to mate - the cuckoo is the only bird that has never seen its parents.

Victorian naturalists put most animal behaviour down to 'instinct' (whatever that may be!) but more modern researchers are interested in learning and development. Most people know how goslings, for example, will imprint on the first moving object they see, taking it for their parent. But cuckoos, it seems, are genetically programmed to recognise each other.

And then there is the mystery of evolution - how did the cuckoo's lifestyle evolve? Most animal adaptations I can understand in terms of natural selection, but this one baffles me.

Even if some absent minded female once accidentally laid her eggs in the wrong nest, how did this develop into the parasitic behaviour of the whole species today? And the birds are very specialised in their niche - details of egg size and colouring, and the physical adaptation of the hatchling to help it eject the other eggs, are all specific to the cuckoo way of life.

Another mystery is how the other bird-brains let cuckoos get away with it!

Very strange.

 

[marion]

I recently heard that not only do the young cuckoos know to fly to Africa a month after their parents but they also fly to the same tree there that their parents live in!

 

[rynner2]

That sounds unlikely, Marion, in view of this:

Because full-grown Cuckoos are really difficult to catch and finding nests with young Cuckoos in is tricky, the number ringed is quite low, so we don’t have much information based on ringing data. We don’t know where in Africa British & Irish birds spend the winter, the only recovery is of a bird ringed as a nestling found in Cameroon in January.

Source

Looking for info on Google has turned up over 26,000 pages - I may be gone some time!

 

[rynner2]

Darwin on Cuckoo evolution (A long read, as CD had a wide knowledge of this and other species.)

And recent news from Australia:-

Bird battle over cuckoo in nest

IT is a deadly arms race involving stealth, subterfuge and murder of the young.

However the players are not opposing geopolitical forces but birds - with the Horsfield's bronze cuckoo on one side and the Australian superb fairy wren on the other.

Canberra researcher Naomi Langmore, whose research is published in the journal Nature tomorrow, has made a discovery about an epic battle of wits between the two species which holds the key to one of the secrets of evolution.

Cuckoos are well known for laying their eggs in the nests of other birds.

When the cuckoo chick hatches, it throws the other eggs and chicks out of the nest, and the host parent unknowingly raises the intruder.

To do this, cuckoo eggs have evolved to closely resemble the eggs of the host.

The host, in turn, evolves defences by becoming very good at spotting the odd egg out.

Unfortunately for the host, the ability to spot odd eggs doesn't extend to spotting odd chicks.

"They always rear the cuckoo chick, so even though they're so good at spotting an egg that's just slightly different they don't spot any difference in the fact they're rearing a chick that looks nothing like their own offspring," Dr Langmore, a research fellow at the Australian National University, said.

"They can be feeding a chick that's five times their own size and they still don't realise there's anything weird about it.

"This has been a big puzzle in evolutionary ecology, why don't hosts evolve the ability to recognise cuckoo chicks?"

Enter the fairy wren.

The wrens are hopeless at recognising foreign eggs, but have an uncanny ability to recognise interloping cuckoo chicks.

Dr Langmore said she had shown that after two or three days the female fairy wren stops feeding the cuckoo chick and begins building a new nest.

The male fairy wren continues to feed the cuckoo for a few more hours but eventually leaves it to mate with the female, leaving the intruder to starve or freeze to death.

"The fairy wrens I've been studying are the first hosts ever found that can recognise cuckoo chicks," Dr Langmore said.

"We think that what's happening is that the fairy wren are completely beaten at the egg stage and they've moved onto the next stage of the arms race and evolved the ability to recognise cuckoo chicks."

Dr Langmore said there was fierce debate in the scientific community about whether the behaviour of one species can influence the evolution of another.

Her findings about this feathered arms race may help put the argument to rest.

Source

 

[marion]

That sounds unlikely, Marion,

Yeah well it was my mother that told me,she can be a bit sensationalist!

 

[mejane]

Facinating stuff.

Most birds (and other animals) do seem to think that the first thing they see is "mother" - so why don't young cuckoos try to mate with wrens? Maybe they do, before discovering the error of their ways?

One thing that has always facinated me about cuckoos is that they seem to specialize in parasiting the nests of smaller birds - why don't they lay their eggs in pigeon nests, for example?

I can't even begin to imagine how the young cuckoos navigate to Africa or, for that matter, how salmon allegedly swim upstream to the very place they were spawned (has anyone checked? how do they know?)

So many mysteries, so little time

Jane.

 

[JamesWhitehead]

The Marsden Cuckoo Day story retold by rynner at the top of the
thread is also familiar as one of the tales of the Wise men of
Gotham in Nottinghamshire. Some sources say that their madness
was feigned to prevent King John building a hunting lodge in the
village.

My source for this is the familiar RD Folklore, Myths & Legends of GB,
which also has the information that before bird migration was understood,
people believed the cuckoo turned into a hawk during the winter
or hibernated in a fairy hill!