探花直播 of Cambridge - cuckoos

Earth, wind and flyer: the moves of Disco Tony and friends

lw355 — Tue, 26 Jul 2016 08:33:28 +0000

Earlier this year, Toby Smith followed the moves of Disco Tony and his fellow cuckoos 鈥� a journey that took him to the forests of Gabon in West Africa and the fringes of the Bat茅k茅 Plateau grasslands.

As a photojournalist 鈥� and first Leverhulme artist-in-residence at the 探花直播 of Cambridge Conservation Research Institute (UCCRI) 鈥� his aim was both to photograph the landscape and to talk to the local villagers and hunters with whom the cuckoos share their home.

探花直播result is a remarkable series of images that is providing bird researchers with a comprehensive idea of the rural landscapes in which the cuckoos overwinter.

探花直播cuckoos all carry tiny lightweight devices that transmit a satellite-trackable signal as they make their arduous journey from breeding grounds in the UK south to Africa. Over the past five years, the signals of around 50 cuckoos have been helping a team of researchers at the British Trust for Ornithology (BTO) gain the first information on what happens to Africa-bound migrant birds after they have left the shores of the UK. 探花直播BTO鈥檚 hope is that this will help solve the mystery of why the cuckoo population has halved in the UK in the past 20 years.

Dr Chris Hewson, who leads the BTO project, explains: 鈥淏efore we started the work, all we knew was that we were seeing a continual drop in cuckoo numbers. We didn鈥檛 know whether this was a result of changes in the UK breeding grounds, or of fatalities on the migration routes or in Africa. But, by tracking the birds, we now know which routes they take and the relative costs of each in terms of mortality, which has led us to begin to understand some of the causes of the decline.鈥�

In fact the cuckoo is not alone in facing an uncertain future, says Juliet Vickery at the RSPB鈥檚 Centre for Conservation Science: 鈥淎round 70% of long-distant migrant bird species that winter in sub-Saharan Africa are declining. For most we don鈥檛 understand why, but the causes are likely to be complex as they face loss of habitat, through human- and drought-related land use change, hunting and climate change, right across the flyway.鈥�

鈥淲e expect birds like cuckoos, swallows, swifts and nightingales to rock up here every summer but what if they don鈥檛 arrive?鈥� adds Professor Bill Adams from the Department of Geography. Four years ago, he teamed up with Vickery, Hewson and researchers at the Department of Zoology to review all of the information available on the fate of the birds in a project funded by the Cambridge Conservation Initiative.

It became clear that really very little was known. In particular, there were few comparative studies on the effects of land use change in regions in Africa frequented by many of the 2.1 billion birds that migrate from Europe during the non-breeding season.

鈥淭hese regions are areas where poverty makes the welfare of urban and rural people the policy priority,鈥� adds Adams. 鈥淥ften what is good news for people 鈥� adapting land to create work and food 鈥� is bad news for birds unless there is a sophisticated understanding of the implications of habitat requirements. Only then can we hope that decision making can support nature too.鈥澛�

Adams and others view Africa as a major gap in knowledge about land use and birds:聽鈥淚n Europe we know a lot about how and why people use rural land, and what this means for migrant birds.聽 But we don鈥檛 know much about rural African landscapes in which birds spend the winter.鈥�

However, a few months ago, an idea began to take shape that could provide a step towards bridging this knowledge gap.

Smith had just taken up his role as artist-in-residence at UCCRI. Speaking to Adams and Hewson about the fate of the cuckoos, he was fascinated: 鈥淚 wondered whether I could follow the cuckoos to Africa. No-one really knows what the cuckoo finds there 鈥� how people fashion a landscape that鈥檚 either friendly or unfriendly for cuckoos. I wanted to contribute to the research project by providing 鈥榚yes on the ground鈥� at their journey鈥檚 end.鈥�

鈥� 探花直播most important element in land use change in this region is the rural household,鈥� explains Adams. 鈥淎nd the opportunity to present the landscapes in photographs that help us understand woodland management and agricultural practice was very attractive.鈥�

Actually spotting a cuckoo, however, was unlikely, as Smith explains: 鈥� 探花直播tracking data is accurate enough to pinpoint where the cuckoos are to within 500 m, but there鈥檚 a delay between the signal being transmitted by the bird鈥檚 tag and being accessible to us in the field, and the forest terrain is vast.

鈥淪eeing a bird would have been epic but, from a visual perspective, it wouldn鈥檛 have told us anything new. I wasn鈥檛 there as a birdwatcher, I was there as a documentary photographer. I was more interested in experiencing and engaging with the natural and social landscape of these birds. Very little scientific attention had been paid to this area 鈥� even Gabon鈥檚 most prolific birder hadn鈥檛 been there in 35 years.鈥�

And so in January 2016, Toby Smith and Malcolm Green, an oral storyteller, arrived in Gabon with hammocks and a petrol stove, hired an off-road vehicle and set off to bush-camp for almost two weeks. Their trip was funded through Flight Lines (a joint project between the BTO and the Society of Wildlife Artists), the Economic and Social Research Council Impact Acceleration account, and Smith and Green themselves. They spoke to hunters and villagers, asking what they knew of the cuckoo 鈥� 鈥渨e used photographs and bird-song recordings to help identify any interactions鈥� 鈥� and Smith photographed the cuckoo鈥檚 habitat of forest margins and grasslands on the Bat茅k茅 Plateau.

Back home, he opened up his photo editing and curating process to conservation specialists like Chris Hewson and other partners in the Cambridge Conservation Initiative 鈥� a unique collaboration between the 探花直播 of Cambridge and biodiversity conservation organisations within the newly opened David Attenborough Building.

鈥淐onservationists have a specific aesthetic interpretation of pictures, and so Chris and others needed to be really involved in the process of selecting which images told an important part of the cuckoo鈥檚 story.

鈥淕enerally, what I found in Gabon was encouraging. 探花直播density of people is so thin that even if the bird was hunted within 40 km of each village there are still huge areas available. It鈥檚 an area of great biodiversity and the villagers are not hugely aware of the cuckoo among the general flora and fauna.

鈥淭here was an incredible mosaic of gallery forest where the water table is accessible beneath the sand. And there were abrupt transitions between savannah landscape and forested landscape 鈥� there鈥檚 a lot of forest edge. From what we know about cuckoo behaviour this suits them to a T.鈥�

鈥淗owever, future land use change in the Gabon is likely to accelerate,鈥� says Hewson. 鈥淭o have Toby鈥檚 eye-witness account now is really important. Even finding that people rarely see cuckoos there is instructive for us 鈥� it shows what we are going to be up against when we go out there. It helps us to piece this together with knowledge of migration routes, to provide a more fully formed idea of what happens to the cuckoo for the major part of its annual cycle.鈥�

Recently, the BTO tracking project has shown for the first time that cuckoos use two different routes to reach Africa (through Italy and across the Sahara, and through Spain and around the edge of West Africa) and that the Spanish route is associated with greater mortality. 探花直播team has found that the use of this route within local breeding populations correlates with population decline. In an article recently published in NatureCommunications, the researchers suggest that this might be linked to severe droughts in Spain, such as in 2012, and raise concerns that a more recent drought in Italy might have further repercussions for the declining cuckoo population.

鈥淯ltimately more research is vital,鈥� says Adams, who has a joint project with Vickery starting next year in Ghana to look at the drivers of land use change and the impact on birds. 鈥淢y hope is that Toby鈥檚 work will contribute towards a common understanding between ornithological researchers and development researchers about the way people and birds share landscapes.鈥�

Meanwhile, as of March 2016, and after no signal for seven weeks, Disco Tony 鈥減opped back up鈥� according to the BTO鈥檚 blog of each of the cuckoo鈥檚 whereabouts. Traced to the Central African Republic, he has begun his long journey back to the bog in Wales.

Why the name Disco Tony? 探花直播Welsh bog in which he was tagged was a particularly challenging environment to work in, with high tussocky grass. To reach the captured cuckoo, bird-ringer Tony Cross had to do a hopping, balancing, disco dance of a run. Naming the cuckoo Disco Tony seemed only appropriate.

www.bto.org/science/migration/tracking-studies/cuckoo-tracking/disco_tony

Disco Tony has travelled over 5,000 miles. He is grey with a yellow ring around his eyes. He is a cuckoo, but not just any cuckoo. He is one of a very special group of birds whose every move is being monitored.

Toby鈥檚 work will contribute towards a common understanding between ornithological researchers and development researchers about the way people and birds share landscapes

Bill Adams

Toby Smith

Gabon

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探花直播reed warbler and the cuckoo: an escalating game of trickery and defence

amb206 — Mon, 22 Feb 2016 10:45:59 +0000

Reed warblers are a little smaller than sparrows and each one weighs no more than a large envelope. As autumn begins they migrate some 5,000 km from Britain to West Africa, a journey they might make just two or three times in their short lives. In April they fly north to breed in the watery landscapes of northern Europe where they raise their young in nests suspended from reeds. Sometimes they are tricked into raising cuckoo chicks which grow to four times their size.聽

In his book聽聽Cuckoo - Cheating by Nature, Nick Davies (Department of Zoology) describes what it鈥檚 like to watch reed warblers at the Cambridgeshire nature reserve of Wicken Fen. He carefully parts the reeds until he can see a pair of warblers feeding their young in a nest. He senses the parents鈥� urgency in collecting insects for their chicks while keeping them warm and staying alert for signs of danger. When several hours later he stands up, the intimate world of the warbler disappears into the great expanse of fenland and the wide East Anglian skies.

Observation remains vital to learning more about the world, believes Davies. 鈥淭here鈥檚 still plenty more to learn from going out into nature and watching carefully,鈥� he says. 鈥淚 get most of my ideas by watching animals and simply asking 鈥業 wonder why they鈥檙e doing that?鈥� 探花直播key to research is coming up with a good question and devising an experiment to answer it.鈥�

Davies, who gives this week's Darwin Lecture (Games Animals Play), has been studying reed warblers at Wicken Fen for more than 30 years. He thinks of them as 鈥榟is鈥� warblers and calls his interest in their lives, and their fragile niche within a changing environment, a kind of obsession. In the process of countless early mornings, and dozens of experiments, he and his colleagues have gradually unlocked some of the secrets of warblers鈥� interactions with cuckoos, who 鈥榩arasitise鈥� other birds.

In an endless game of trickery and defence, the cuckoo and its hosts engage in an 鈥榓rms race鈥� involving mimicry of many kinds 鈥� from the patterning of eggs to the demanding twittering of chicks 鈥� as the two species weigh up the risks of being duped and discovered. Reed warblers sometimes reject eggs that don鈥檛 look like their own 鈥� but what evidence does a warbler need before it takes such drastic action?聽 Recent research reveals that warblers eject suspect eggs from their nests only when local information is reinforced by signals from a wider 鈥榥eighbourhood watch鈥�.

Davies鈥檚 fascination for birds stems from a childhood spent on the Lancashire coast where the skies were full of skeins of pink-footed geese and the sand dunes were home to croaking natter jack toads. He got his taste for patient observation, for asking difficult questions (why, for example, does the reed warbler accept a cuckoo chick so obviously different to one of its own?), and interest in detective work from Niko Tinbergen, a pioneer of scientific studies of animal behaviour. As an evolutionary biologist, Davies is also respectful of the observational studies of the early naturalists who laid the foundations for subsequent experimental work.

探花直播remarkable insights explored so vividly in Cuckoo - Cheating by Nature would have been impossible without research collaborations, often international. Birds migrate vast distances: to understand them, and how they鈥檙e shaped by evolution, requires an investigation of every aspect of their lives. Within the same species, there are behavioural variations which offer clues to their evolutionary pathways. To get a picture of the different 鈥榬aces鈥� of cuckoos (categorised by the species they parasitise to host their young) Davies has worked with biologists across the world.

He says: 鈥淪ome of the most exciting discoveries are now being made in Africa by Claire Spottiswoode and in Australia by Naomi Langmore. In both places, the arms race between cuckoos and hosts has been going on much longer and has escalated to new levels. For example, in Australia some hosts reject chicks unlike their own and their cuckoo has combated this by evolving a mimetic chick. And in Africa, cuckoo hosts have the most remarkable egg signatures in the form of individual spots and squiggles which makes it easier for them to detect a foreign egg.鈥�

In the accompanying podcast, Davies talks about the games animals play with particular reference to the dunnock, a small brown bird with a surprisingly inventive sex life. 聽

探花直播lecture Games Animals Play will take place in the Lady Mitchell Hall, Sidgwick Site, 探花直播 of Cambridge, on Friday, February 26, 2016 - 17:30 to 18:30. No booking required, no charge. Arrive in good time to secure a seat.

Main image: a reed warbler feeds a cuckoo fledgling (https://www.richardnicollphotography.co.uk/) Inset images:聽a clutch of reed warbler eggs with a larger cuckoo egg (Nick Davies); a meadow pipit feeds a cuckoo fledgling (Charles Tyler).

Professor Nick Davies, who gives this week鈥檚 Darwin Lecture, has been studying reed warblers for more than 30 years 鈥� and has unlocked many of the secrets of their interactions with the cuckoo. His work shines light on the evolutionary games played out in nature as species compete with environmental pressures, with other species, and with the opposite sex, to pass on their genes.

I get most of my ideas by watching animals and simply asking 鈥業 wonder why they鈥檙e doing that?鈥� 探花直播key to research is coming up with a good question and devising an experiment to answer it.

Nick Davies

Richard Nicoll

A reed warbler feeds a cuckoo fledgling

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Neighbourhood watch and more: how reed warblers watch out when there鈥檚 a cuckoo about

amb206 — Fri, 22 Jan 2016 12:00:00 +0000

It鈥檚 a risky business being a reed warbler. Not only do these tiny birds embark on an annual migration of some 5,000 km from their West African winter quarters聽to breeding grounds in the north, but they are also 鈥榟osts鈥� to the cuckoo, a species that lays its eggs in other birds鈥� nests and takes no further part in raising its offspring. When the cuckoo chick hatches, it pushes the reed warbler eggs and young out of the nest. As sole occupant, it tricks its warbler 鈥榩arents鈥� into supplying its voracious appetite until it fledges.

Cuckoos are expert tricksters: their eggs mimic those of their hosts in pattern though they are a little bigger. If the reed warbler detects an alien egg in its nest, or spots a cuckoo nearby, it may eject the odd-looking egg. But cuckoos are so swift in laying their eggs (only one is laid per nest and the process is over in as little as 10 seconds), and so clever at disguising their eggs, that warblers are often uncertain whether an odd egg in the clutch is a cuckoo egg or one of their own.

Research into the relationship between cuckoos and reed warblers has to date concentrated on the behaviour of individual birds and their interactions with cuckoos, described as parasites. A new study published today (22 January 2016) in Scientific Reports looks at wider interactions between neighbouring communities of reed warblers, their strategies for coping with cuckoos, and, in particular, how warblers assess levels of risk by gathering information from a variety of sources.

After two years of observation of warblers that spend the breeding season at Wicken Fen in Cambridgeshire, authors Rose Thorogood and Nicholas Davies (Department of Zoology) reveal that a kind of 鈥渘eighbourhood watch鈥� exists out in the reed beds, keeping birds up-to-date with the latest threats. Using a series of controlled experiments, involving model cuckoos and broadcasts of reed warbler alarm calls, the researchers revealed that reed warblers factored information gathered from close surveillance of the neighbourhood into their decision-making when assessing whether or not to eject an egg.

When reed warblers spot a cuckoo, they may mob it and emit alarm calls that carry up to 40 metres. These alarm calls attract neighbours, who come to investigate the cause of the commotion. But the sound of neighbourly mobbing of a cuckoo alone is insufficient to prompt warblers to eject a suspect egg from their own nests. They also need clues that suggest a more close-up and personal threat.

鈥淲e found that warbler pairs ejected an odd egg only when there was strong evidence that it might not be one of their own.聽 For action to be taken, the clues had to add up. 探花直播warblers needed to be alerted by their neighbours鈥� behaviour that there was a cuckoo at large in the neighbourhood 聽and they needed to be aware of a more local and imminent threat, by seeing 聽a cuckoo near their own nest. 鈥� said Thorogood.

鈥淣either personal encounters nor social encounters alone were sufficient to stimulate egg rejection. Instead, information was combined from both these sources. This is fascinating because we have assumed previously that animals favour one type of information over the other 鈥� for example, experiments show that some fish species will ignore where their shoal mates forage if they already have information about the location of food themselves, even when it is less profitable. Here we show that combining information is the best way to take the most appropriate course of action.鈥�

探花直播use of multiple sources of information has important consequences for cuckoos too. With their neighbourhood abuzz with information, cuckoos need to be wary of alarming potential hosts.

鈥淏ecause the information warfare between cuckoos and their hosts extends well beyond individual interactions, there鈥檚 pressure on cuckoos to be increasingly secretive, not only to avoid alerting their target host pair, but also other host pairs in the local neighbourhood鈥� said Thorogood.

Cuckoo numbers have declined by as much as 60% in the past 30 years for reasons that remain unclear. At Wicken Fen, where several hundred warblers arrive to breed each May, between 10% and 20% of reed warblers nests were used by cuckoos. Today only 2% of warbler nests at Wicken host cuckoos. This rapid drop in cuckoo numbers, which contrasts with a stable warbler population, has enabled Thorogood and Davies to track how the warblers have dropped their defences in concert with the dramatic decrease in cuckoo threat.

Davies has been researching cuckoos and their hosts at Wicken Fen since the 1980s. He said: 鈥淩eed warblers are much less likely to eject an egg from their nest today than they were in the 1980s. This makes complete sense. They have matched their behaviour to the changing level of risk. Most reed warblers have just one or two summers in which to breed. So every opportunity to mate, construct a nest and raise a clutch of eggs is precious. If a pair of warblers mistakenly identifies one of their own eggs as a cuckoo egg and chucks it out, or deserts the nest, the loss is great. Our work shows how they match their defences to the risk of parasitism.鈥�

A study of reed warbler behaviour reveals for the first time that in assessing the risks posed by cuckoos the birds combine information from multiple sources. An 鈥榠nformation highway鈥� provides one set of clues and personal encounters another. Only when both add up, do the birds take defensive action.

Warbler pairs ejected an odd egg only when there was strong evidence that it might not be one of their own. For action to be taken, the clues had to add up.

Rose Thorogood

Richard Nicholl

A cuckoo chick ejects a reed warbler egg from a nest

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Cuckoos mimic 'harmless' species as a disguise to infiltrate host nests

fpjl2 — Wed, 10 Jun 2015 13:26:21 +0000

Brood parasites are reproductive cheats that evolve ways of duping other birds into raising their young. Examples such as mimicry of host eggs, chicks and fledglings by brood parasitic eggs, chicks and fledglings are amongst the most iconic examples of animal deception in nature.

New research shows that adult brood parasitic female cuckoo finches have evolved plumage colours and patterns to mimic a harmless and abundant species, such as southern red bishops, to deceive possible host birds and reduce the risk of being attacked when approaching host nests to lay their eggs.

Researchers say this is the first time that "wolf in sheep's clothing" mimicry has been shown to exist in any adult bird.

While other brood parasites watch the movements of their host victims by hiding in nearby foliage, the openness of the African savannahs mean that mimicking a plentiful and nontoxic species might be the best way cuckoo finches have of sneaking up on host nests without raising the alarm.

However, the researchers found that the most common victim of the cuckoo finch, the tawny-flanked prinia, has evolved an awareness of the cuckoo finch's disguise and takes no chances - acting with equal aggression towards a female cuckoo finch and bishop alike.

Prinias attacked female cuckoo finches and female bishops equally, and increased the rate of egg rejection after seeing either a female cuckoo finch or female bishop near the nest. Egg rejection involves physically removing the parasitic egg from their nest, allowing them to salvage the majority of their reproductive effort.

At the study site in Zambia, the researchers found a consistently high rate of parasitism by cuckoos among the prinia population, with almost a fifth of all prinia eggs hatching as fledgling cuckoo finches. Cuckoo finches usually remove at least one egg on parasitism, and their hatchlings will out-compete all the host's young.

Researchers say these rates of parasitism might explain the willingness of prinias to attack anything that looks like a dangerous female cuckoo finch and reject more eggs when the risk of parasitism is high. But, the cost of this strategy can be high: during the researchers' experiments, some of the eggs rejected by prinia were their own, triggered by nothing more than a harmless bishop bird that resembles the mimetic cuckoo finch.

"Our findings suggest that female cuckoo finches are aggressive mimics of female bishops, and that prinia hosts have responded to this successful deception with generalised defences against cuckoo finches and harmless bishops alike. This suggests these prinias have decided that it's best to 'play it safe' when the risk of parasitism is high because they can't distinguish between the two species" said Dr William Feeney from Cambridge 探花直播's Department of Zoology, who led the research.

"While other brood-parasite species monitor host behaviour from concealed perches in nearby trees, cuckoo finches must seek host nests in open grasslands and savannahs. In such exposed circumstances, resembling an abundant and harmless model may allow female cuckoo finches to remain unnoticed when monitoring hosts nests at a medium range," he said.

探花直播research is published today in the journal Proceedings of the Royal Society B.

To investigate the cuckoo finch's disguise, the research team conducted plumage and pattern analysis using cuckoo skins from the Natural History Museum in Tring. They compared plumage to the cuckoo finches closest evolutionary relatives (Vidua finches), as well as with the skins of similar-looking birds (bishops) that share the same habitat.

In both human and bird visual systems, they found that the plumage of a female cuckoo finch is far closer to the bishops and other species in the weaver family than to those of its closest relative, the Vidua finches.

探花直播researchers also investigated the reaction of prinia breeding pairs to models of female cuckoo finches and bishop birds, as well as the males of both species.

While prinias had very little reaction to the males, the female cuckoo finch and the harmless female bishop bird both received similarly high levels of alarm calls and group attacks from the prinia, known as 'mobbing'.

探花直播researchers then did a final experiment where they presented a male bishop, female bishop and female cuckoo finch and then placed a fake egg in their nest. They found that after seeing the harmful female cuckoo finch or harmless (but similar-looking) female bishop, they increased their rate off egg rejection compared to when they saw a male bishop near their nest.

Added Feeney: "This study is interesting as it's the first time anyone has quantitatively tested for 'wolf in sheep's clothing' mimicry in any adult bird, and also suggests that this type of mimicry is used by brood parasites to deceive hosts at all stages of their nesting cycle."

First time 鈥榳olf in sheep鈥檚 clothing鈥� mimicry has been seen in birds. Host birds have evolved a general counter-strategy in which they defend against all birds with the mimicked plumage - cuckoos and harmless species alike.

It's the first time anyone has quantitatively tested for 'wolf in sheep's clothing' mimicry in any adult bird

William Feeney

Claire Spottiswood

Cuckoo finch on the left and a bishop bird on the right

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Birds evolve 鈥榮ignature鈥� patterns to distinguish cuckoo eggs from their own

fpjl2 — Wed, 18 Jun 2014 09:36:32 +0000

For some birds, recognising their own eggs can be a matter of life or death.

In a new study, scientists have shown that many birds affected by the parasitic Common Cuckoo - which lays its lethal offspring in other birds鈥� nests - have evolved distinctive patterns on their eggs in order to distinguish them from those laid by a cuckoo cheat.

探花直播study reveals that these signature patterns provide a powerful defense against cuckoo trickery, helping host birds to reject cuckoo eggs before they hatch and destroy the host鈥檚 own brood.

To determine how a bird brain might perceive and recognize complex pattern information, Dr Mary Caswell Stoddard at Harvard 探花直播 and Professor Rebecca Kilner and Dr Christopher Town at the 探花直播 of Cambridge developed a new computer vision tool, NATUREPATTERNMATCH. 探花直播tool extracts and compares recognizable features in visual scenes, recreating processes known to be important for recognition tasks in vertebrates.

鈥淲e harnessed the same computer technology used for diverse pattern recognition tasks, like face recognition and image stitching, to determine what visual features on a bird鈥檚 eggs might be easily recognised,鈥� explained Stoddard.

Using the tool, the researchers studied the pigmentation patterns on hundreds of eggs laid by eight different bird species (hosts) targeted by the Common Cuckoo.

They discovered that some hosts, like the Brambling, have evolved highly recognisable egg patterns characterised by distinctive blotches and markings. By contrast, other hosts have failed to evolve recognisable egg patterns, instead laying eggs with few identifiable markings. Those hosts with the best egg pattern signatures, the researchers found, are those that have been subjected to the most intense cuckoo mimicry.

探花直播Common Cuckoo and its hosts are locked in different stages of a co-evolutionary arms race. If a particular host species 鈥� over evolutionary time 鈥� develops the ability to reject foreign cuckoo eggs, the cuckoo improves its ability to lay eggs that closely match the colour and patterning of those laid by its host.

鈥� 探花直播ability of Common Cuckoos to mimic the appearance of many of their hosts鈥� eggs has been known for centuries. 探花直播astonishing finding here is that hosts can fight back against cuckoo mimicry by evolving highly recognisable patterns on their own eggs, just like a bank might insert watermarks on its currency to deter counterfeiters,鈥� said Stoddard.

鈥� 探花直播surprising discovery of this study is that hosts achieve egg recognition in different ways鈥� said Kilner, from Cambridge鈥檚 Department of Zoology.

Some host species have evolved egg patterns that are highly repeatable within a single clutch, while other species have evolved eggs with patterns that differ dramatically from female to female in a population. Still other host species produce egg patterns with high visual complexity. Each strategy is effective, increasing the likelihood that a given host will identify and reject a foreign egg. 鈥淪ome species use two of these strategies, but none uses all three,鈥� continued Kilner. 鈥淎 signature like this would be too complex to be easily recognised鈥�.

探花直播patterns on bird eggs are just one type of visual signature. Identity signatures are common in the animal world, but how they are encoded and recognised is poorly understood. In the future, computational tools like NATUREPATTERNMATCH - which account for important aspects of visual and cognitive processing - will be crucial for understanding the evolution of visual signals in diverse biological populations.

探花直播findings of this study are reported in the journal Nature Communications.

Inset image: Reed Warbler caring for Cuckoo chick. Credit: David Kjaer

Using new 鈥榩attern recognition algorithm,鈥� latest research highlights how birds are 鈥榝ighting back鈥� against the parasitic Common Cuckoo in what scientists describe as an evolutionary 鈥榓rms race鈥�. They found that birds with the most sophisticated and distinctive egg patterning are those most intensely targeted by the cuckoo鈥檚 egg mimicry.

探花直播surprising discovery of this study is that hosts achieve egg recognition in different ways

Rebecca Kilner

Mary Caswell Stoddard/Natural History Museum

NATUREPATTERNMATCH extracts visual features, here represented by magenta vectors (left). Three eggs each (represented in different rows) laid by three different Great Reed Warblers are shown here (right).

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Cuckoos impersonate hawks by matching their 'outfits'

fpjl2 — Thu, 17 Oct 2013 09:11:54 +0000

New research shows that cuckoos have striped or 鈥渂arred鈥� feathers that resemble local birds of prey, such as sparrowhawks, that may be used to frighten birds into briefly fleeing their nest in order to lay their parasitic eggs.

By using the latest digital image analysis techniques, and accounting for 鈥渂ird vision鈥� - by converting images to the spectral sensitivity of birds - researchers have been able to show for the first time that the barred patterns on a cuckoo鈥檚 breast may allow it to impersonate dangerous birds of prey. This might enable cuckoos to frighten other avian hosts into leaving their nests exposed.

探花直播latest findings, published today in the journal Animal Behaviour, expand the cuckoo鈥檚 arsenal of evolutionary deceptions, which include egg mimicry and chick mimicry that allow it to trick other birds into incubating its eggs.

Importantly, the study shows that a wide variety of cuckoos have adapted different plumage patterns depending on the area they inhabit so that they match a local bird of prey species.

While scientists have previously looked at links in plumage patterns between the common cuckoo and Eurasian sparrowhawk, the new research shows that this type of impersonation of a more dangerous animal 鈥� called 鈥楤atesian mimicry鈥� 鈥� may be far more widespread in cuckoos. In addition, the dangerous bird of prey that cuckoos resemble goes beyond sparrowhawks to include such raptors as bazas and harrier-hawks - depending on the species prevalent in the cuckoo鈥檚 neighbourhood.聽聽聽聽

鈥淭here is no benefit in looking like a dangerous species your target is not familiar with,鈥� said lead researcher Thanh-Lan Gluckman from Cambridge鈥檚 Department of Zoology.聽聽聽聽聽聽

鈥淲e first established similarity in plumage pattern attributes between cuckoos and raptor species, and then showed that cuckoos look nothing like species from a different geographical area.鈥�

探花直播cuckoos also use their crafty 鈥榟awk impression鈥� to allow them to fly 鈥榰nder the radar鈥�, undetected as they scope out potential nests in which to deposit their parasitic eggs.

鈥� 探花直播barring on their plumage helps cuckoos conceal themselves while searching for potential nests, then when they approach, the host of the nest may mistake a cuckoo for a raptor coming to get them 鈥� giving them unfettered access to lay eggs,鈥� Gluckman said.聽

While previous studies have focused on Batesian mimicry in the common cuckoo and Eurasian sparrowhawk, this is the first time that the plumage patterns of cuckoos have been analysed using digital image analysis techniques. 探花直播study suggests that this form of mimicry may be widespread among many cuckoo species, and that they may be mimicking a variety of different types of birds of prey.聽

探花直播researchers were surprised to find no pattern matching between cuckoos and raptors that live in different geographical areas, showing that the visual similarity is highly localised to species in the immediate vicinity.

鈥淭hese findings underscore the importance of using digital image analysis to objectively quantify plumage patterning in mimicry 鈥� it is important not to make assumptions about even simple patterns such as these,鈥� added Gluckman.

鈥淲e hope this encourages other researchers to examine the function of barred plumage in parasitic cuckoos and raptors the world over.鈥�

Another interesting finding is that of the African cuckoo-hawk, a raptor so named because of its visual resemblance to cuckoos. This study objectively shows that the naming was an apt one, given that a local cuckoo matched the African cuckoo-hawk in all of the pattern attributes measured.

One of the earliest observers of the cuckoos鈥� invasive guile was Ancient Greek philosopher Aristotle, who noted some 2,300 years ago that it 鈥渓ays its eggs in the nest of smaller birds鈥�.

Evolutionary trick allows cuckoos to mimic the plumage of birds of prey, and may be used to scare mothers from their nests so that cuckoos can lay their eggs. Mimicry in cuckoos may be more much more widespread than previously thought.

There is no benefit in looking like a dangerous species your target is not familiar with

Thanh-Lan Gluckman

Thanh-Lan Gluckman/Gabriel A. Jamie

Left: Cuckoo compared to cuckoo-hawk plumage. Right: Cuckoo

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Biological arms races in birds

gm349 — Wed, 13 Apr 2011 09:56:24 +0000

Brood parasitic birds such as cuckoos lay eggs that mimic those of their hosts in an effort to trick them into accepting the alien egg and raising the cuckoo chick as one of their own.

New research from the 探花直播 of Cambridge has found that different bird species parasitised by the African cuckoo finch have evolved different advanced strategies to fight back.

One strategy is for every host female to lay a different type of egg, with egg colour and pattern varying greatly among nests.聽 These egg 'signatures' make it harder for the cuckoo finch to lay accurate forgeries. Since the female cuckoo finch always lays the same type of egg throughout her lifetime, she cannot change the look of her egg to match those of different host individuals - thus her chances of laying a matching egg are exasperatingly small.

Dr Claire Spottiswoode, a Royal Society Dorothy Hodgkin Research Fellow from the 探花直播 of Cambridge鈥檚 Department of Zoology, said: 鈥淎s the cuckoo finch has become more proficient at tricking its hosts with better mimicry, hosts have evolved more and more sophisticated ways to fight back.聽 Our field experiments in Zambia show that this biological arms race has escalated in strikingly different ways in different species.聽 Some host species 鈥� such as the tawny-flanked prinia 鈥� have evolved defences by shifting their own egg appearance away from that of their parasite. And we see evidence of this in the evolution of an amazing diversity of prinia egg colours and patterns.

鈥淭hese variations seem to act like the complicated markings on a banknote: complex colours and patterns act to make host eggs more difficult to forge by the parasite, just as watermarks act to make banknotes more difficult to forge by counterfeiters.鈥�

探花直播researchers also found that some cuckoo finch hosts use an alternative strategy: red-faced cisticolas lay only moderately variable eggs but are instead extremely discriminating in deciding whether an egg is their one of their own. Thanks to their excellent discrimination, these hosts can spot even a sophisticated mimic.

Dr Martin Stevens, a BBSRC David Phillips Research Fellow from the 探花直播 of Cambridge鈥檚 Department of Zoology, commented on this aspect of the findings: 鈥淥ur experiments have shown that these different strategies are equally successful as defences against the cuckoo finch.聽 Moreover,聽one species that has done a bit of both 鈥� the rattling cisticola 鈥� appears to have beaten the cuckoo finch with this dual strategy, since it is no longer parasitised. 探花直播arms race between the cuckoo finch and its host emphasises how interactions between species can be remarkably sophisticated especially in tropical regions such as Africa, giving us beautiful examples of evolution and adaptation.鈥�

Their findings are reported today in the journal Proceedings of the Royal Society B.

New research reveals how biological arms races between cuckoos and host birds can escalate into a competition between the host evolving new, unique egg patterns (or 鈥榮ignatures鈥�) and the parasite new forgeries.

As the cuckoo finch has become more proficient at tricking its hosts with better mimicry, hosts have evolved more and more sophisticated ways to fight back.

Dr Claire Spottiswoode, a Royal Society Dorothy Hodgkin Research Fellow from the 探花直播 of Cambridge鈥檚 Department of Zoology

Claire Spottiswoode

Image shows a variety of cuckoo finches each adapted to mimic a different host species or colour morph

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Bird鈥檚 eye view of how cuckoos fool their hosts

bjb42 — Fri, 23 Apr 2010 00:00:00 +0000

探花直播finding offers unique insights into a 20 million-year-old evolutionary arms race.

Only seven groups of birds in the world have evolved as brood parasites, laying their eggs in other birds' nests, and ecologists have long been fascinated by this behaviour as an example of evolution in action.

Dr Claire Spottiswoode and Dr Martin Stevens of the 探花直播 of Cambridge worked on two tropical African species, the parasitic Cuckoo Finch and one of its hosts, the Tawny-flanked Prinia.

Until recently, most work on cuckoos has been done in temperate regions - Europe and North America - where species are relatively young in evolutionary terms. In the tropics, however, the Cuckoo Finch and Prinia could have been locked together in an evolutionary arms race for up to 20 million years.

As parasites have evolved ever better manipulation of their hosts, hosts have responded with ever more refined defences to evade parasitism. As a result, the Cuckoo Finch's mimicry of host eggs is extraordinary, as is the Prinias' ability to spot the parasite's eggs.

According to Dr Spottiswoode: "Prinias lay probably the most diverse range of eggs of any bird in the world, and this is likely to be an outcome of the long co-evolutionary battle with the Cuckoo Finch."

" 探花直播eggs are analogous to a bank note, in terms of the variety and complexity of markings, perhaps to make them very hard to forge by the parasite."

To find out exactly how Prinias detect the foreign eggs, Spottiswoode and Stevens set up more than 100 rejection experiments in southern Zambia, putting one Prinia egg into another's nest and waiting to see if the egg was rejected.

They also collected data to feed into a computer model to give them a bird's eye view of the world, using a spectrophotometer to measure egg colours and a digital camera to analyse the eggs' complex patterns.

In the past, this kind of analysis was tackled by humans comparing eggs by eye, but human vision differs hugely from that of a bird. Birds can see ultraviolet light and because they have four types of cone in their eyes, compared with three in humans, they see a greater diversity of colour and pattern.

Spottiswoode and Stevens found that Prinias are amazingly good at rejecting foreign eggs, and that they use colour and several aspects of pattern to spot the parasite's eggs. Mysteriously, however, they do not seem to use the scribbles that uniquely occur only on the Prinias' eggs.

探花直播specific traits used to distinguish foreign eggs were exactly those found to differ most between host eggs and real parasitic eggs. This suggests that natural selection is currently acting to make Cuckoo Finch eggs better mimics of their hosts', and also that Prinias use the most reliable information available in making rejection decisions.

探花直播work was funded by the Royal Society and the DST/NRF Centre of Excellence in South Africa, and is published in PNAS ( 探花直播Proceedings of the National Academy of Sciences of the United States of America) today.

Using field experiments in Africa and a new computer model that gives them a bird's eye view of the world, Cambridge scientists have discovered how a bird decides whether or not a cuckoo has laid an egg in its nest.

探花直播eggs are analogous to a bank note, in terms of the variety and complexity of markings, perhaps to make them very hard to forge by the parasite.

Dr Claire Spottiswoode

CaptPiper from Flickr

探花直播Cowbird's Nest

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