Cuckoo birds aren’t just the inspiration for intricate clocks. They’re also shameless parasites. Brood parasites, that is. Many species of cuckoos have been known to leave their eggs in other birds’ nests, letting their young be raised by entirely different species. Scientists used to think that cuckoos would simply wait for the opportune moment (when the original parent was out of the nest or distracted) to lay their eggs, but it turns out that cuckoos are way more brazen than that. Continue reading
Like a lot of birds, superb fairy wrens of Australia have a problem: Cuckoos lay their eggs in the fairy wrens’ nests. This is called brood parasitism, and it’s how cuckoos manage to have their baby birds raised well without any effort on their part. They leave the messy parts of parenthood to other birds.
Those other birds, though, don’t want to spend their time and effort raising someone else’s kid, especially when that kid might push out the chicks that actually belong in the nest. But the fairy wrens don’t prevent Horsfield’s bronze cuckoos from laying eggs in their nests because the cuckoos look too much like Accipiter hawks, which prey on fairy wrens. Make the wrong call when trying to stop the invader and the fairy wren might end up dead. Continue reading
London – They are notorious for their feckless parenting skills, leaving their offspring to be cared for by others. Now, it seems, cuckoos have other socially reprehensible characteristics: they are fraudsters.
Zoologists from Cambridge University have shown how the cuckoo’s plumage allows the bird to pass itself off as a hunting bird of prey such as a sparrowhawk. By mimicking local predators, cuckoos are able to scare off birds from their nests, allowing them to replace any eggs with their own.
Four cuckoos have been caught and fitted with satellite tags in an effort to track their migrations from Scotland.
The birds were caught by a team from the British Trust for Ornithology who will track them throughout the year.
Cuckoos were once widespread across Britain but recently their numbers have been going down in the south of the country.
Every year the birds fly from the UK to the Congo Basin in Africa to escape the cold weather.
The team hope that by tracking the birds they’ll be able to find out why their habits are changing.
John Calladine, who’s working on the project, said; “An important part of this work will be in identifying areas and habitats used by the birds throughout the year, even across years.”
A cuckoo returning to Ceredigion from migration in Africa has taken a holiday in France to avoid the UK weather.
David the cuckoo returned to the UK from the Democratic Republic of the Congo last Friday but turned back on reaching Somerset.
Bird experts say he could either wait until the weather warmed up or take a short European break.
Five Welsh cuckoos were fitted with satellite tags in May 2012 to monitor their migration paths.
The five birds – Idemili, David, Iolo, Lloyd and Indy – left Ceredigion in spring 2012 for Africa. They travelled over East Anglia, through Holland, Germany and Italy before reaching North Africa.
The main reason for the journey is the hunt for their main food source: caterpillars.
The birds bypass the dry climates of northern Africa because caterpillars cannot survive there, and head for the wetter countries of Cameroon and the Democratic Republic of the Congo where caterpillars thrive.
“The cuckoos are caterpillar experts”, said Paul Stancliffe, a spokesman for the British Trust for Ornithology (BTO).
“Fatty caterpillars fuel their flight. The birds store the fat on their throat, in the loops around their stomach and on their flanks and thighs”, he said.
‘Sound of spring’
The cuckoo population declined by 27% in Wales in the decade up to 2009 compared to 49% in England and 9% in Scotland.
“Cuckoo populations are declining rapidly in some parts of Britain: we want to find out why”, said Dr Chris Hewson, who led the tagging project for the BTO.
“Cuckoos only spend two months in the UK and 10 months elsewhere, so this is how we can find out what is happening to them.
“They are the sound of spring and the sound of the British countryside. They are a culturally resonant bird and people care about their conservation.”
The project has been running for two years in England and Scotland, starting in Wales last year. The £2,500 trackers transmit for 10 hours, then have a 48 hour break to recharge.
David flew over north-western Spain last Wednesday, crossed the Bay of Biscay and flew to Yeovil, Somerset, on Friday.
After finding the weather in Yeovil unbearable he turned back across the English Channel and arrived in Bois, France, on Saturday.
“This is the first time we have observed this,” said Mr Stancliffe.
“We have suspected that birds turn to Europe if the UK is too cold, but we have never seen it.
“We have always wondered, if it is too cold or wet when they arrive, do birds lay low until it warms up, or do some birds head back across the channel and wait there? Now we know that some do return to Europe.”
Dr Hewson said that this was the first time that reverse migration had been tracked.
“Before the project we knew about reverse migration but only anecdotally,” he said.
“People would say they would hear cuckoos one day, then they would disappear … now we know that this is true.”
Only two of the five tagged Welsh birds are still traceable. Indy survived a storm in Libya and after spending two weeks resting in northern Italy is thought to have been eaten by predators in Congo.
Iolo died crossing the Sahara last Autumn.
Idemili, from Carmarthen, was flown on a British Airways flight to Turin in 2012 after spending a few weeks in hospital in Essex.
Lloyd had crossed most of Sahara and was last located in southern Algeria heading toward the Mediterranean.
Last year Scottish cuckoo Chance flew back to Loch Katrine after migration.
The BTO are still waiting to see if David and Lloyd finally come back to Ceredigion.
source : bbc.co.uk
Some birds use a different breeding strategy to others to avoid cuckoos infiltrating their nests, say scientists.
Cuckoos are known for laying their eggs in the nests of other birds, leaving the unsuspecting nest-owner to bring up the cuckoo as one of her own. But some birds are able to avoid this whilst others are targeted. Scientists had no idea why some can always escape, so an international team went to find out.
The study, published in Journal of Animal Ecology, found some female magpies can evade cuckoo parasitism by strategising when and how they build their nests.
‘Almost 30 per cent of magpie females manage to escape parasitism through their lives, whereas the rest are parasitised, at least sometimes,’ says Dr Mercedes Molina-Morales, lead author of the research, from the University of Granada.
The study was shows that these magpies have specific traits that put cuckoos off. ‘It was surprising that despite high rates of parasitism in the population some years, there were females that consistently escaped parasitism, and that we could characterize them in terms of their phenotypic traits,’ explains Molina-Morales.
Phenotypic traits are expressions of genes, like eye colour, but traits which can change depending on the environment. In magpies most phenotypic traits like body size and bill length have no bearing on whether or not a bird avoids parasistism, but the trait determing when the magpie chooses to breed did.
The ones who were most successful built large nests early in their breeding season. Early in the season the trees are bare and all nests are easily visible to cuckoos. During this time smaller nests have fewer sticks in their roofs and more entrances, making them more accessible and more likely to be targeted. So, magpies with larger, less-accessible, nests are more likely to escape parasitism.
But later in the breeding season it is the magpies who build small nests who evade cuckoos. This may be because trees become leafier and smaller nests are more easily hidden, so magpies that build small nests and conceal them in wooded areas are less likely to find a cuckoo moving in.
To leave their eggs in magpie’s nests, the cuckoos normally distract the magpies. ‘The males fly around the nest making noises and attracting the magpies. Then females fly into the nest and lay the eggs in a few seconds, from the rim of the nest,’ Molina-Morales says.
Leaving other mothers to rear their young greatly benefits the cuckoo. It means cuckoos can ‘save energy in most parental duties, such as incubation or chick feeding which allows an increase in the number of eggs that a female can lay in a breeding season,’ says Molina-Morales.
But to promote its own wellbeing, the cuckoo jeopardises the health and life of other birds. A cuckoo in the nest will eat all of the food, starving young magpies. Cuckoo eggs can also sometimes break the magpie eggs when falling on them.
Birds that are able to consistently prevent their nests from being targeted avoid this and their young have a better chance of survival. ‘The 30 per cent of females which avoid parasitism are more successful since they are able to rear twice the number of chicks than those that are parasitized,’ explains Molina-Morales.
The next stage is for the team to find out what the mother does next if she finds her nest subject to a cuckoo invader.