Nov. 19, 2010
Courtesy of BBSRC and World Science staff
In what some scientists are likening to a mob protection racket, a species of birds in Africa has been found to guard other birds from predators in exchange for food.
On one level, the security service offered by the drongo birds of the Kalahari Desert would seem to be legitimate. They do provide some true protection—unlike quite a few mafiosos, who create the very threat that for a fee they will supposedly ward off.
Yet there’s a hint of the criminal in the drongo operation too, scientists say. The avian guards help themselves to “payment” by occasionally screaming out false warnings of predators, then using the resulting confusion to snatch food from their feathered clients. Nor do the latter seem to specifically request protection; rather, the drongos are just—there.
The drawbacks notwithstanding, the “client” birds, pied babblers, gain something from the arrangement, according to scientists. That’s because the self-appointed sentinels, through their presence, allow the babblers to focus on foraging for insects rather than watching their backs.
The behavior may be a rare example of two species evolving from a parasitic to a “mutualistic” relationship, say the investigators, reporting the findings in the research journal Evolution.
“Drongos are parasitic birds who swoop in to steal food from other species,” explained Andrew Radford the Universities of Bristol, U.K., one of the researchers. Given this unsavory way of life, he went on, it was somewhat surprising to find that drongos perched above foraging babblers advertise their presence rather than keep a low profile.
They announce themselves “by issuing a call called a ‘twank’ every four or five seconds,” Radford said.
The explanation, he added, seems to be that the “twank” reassures babblers someone is keeping a lookout against predatory birds. This lets the babblers forage for insects more effectively. That, in turn, leads to better opportunities for the drongos to filch some of the catch. “When we played back these ‘twank’ calls to a babbler group, we found that they spread out over a larger area and lifted their heads less often, indicating that they were less fearful of predators when they thought a drongo was keeping watch,” Radford said.
But when the drongos cry wolf about the presence of predators, they scare other animals into dropping their catch, which the drongos then pounce on, said Radford and colleagues. So pied babblers have basically evolved to tolerate the drongos giving false warnings and stealing some of their hard-earned gains in exchange for the chance to forage in relative safety when a drongo is on duty.
Like a “good gangster,” Radford said, the drongos—not particularly large birds—provide real protection sometimes, both by making true alarm calls and by “mobbing” predators as a group.
But “despite all of the useful services drongos provide, the foraging birds are still more responsive to [alarm] calls from other babblers. It seems likely that the babblers simply don’t trust the drongo mafia as much as their own flesh and blood.”
The research could provide insight into other important mutualistic and parasitic relationships in nature, said Douglas Kell, chief executive of the U.K. Biotechnology and Biological Sciences Research Council, which funded the study. “Evolutionary arms races, including those between parasites and their hosts, and plants and animals and the diseases that they suffer, underlie a whole range of socially and economically important areas of biology,” he noted.
http://www.world-science.net/othernews/101119_racket.htm
Showing posts with label drongos. Show all posts
Showing posts with label drongos. Show all posts
Saturday, November 20, 2010
"Gangster" bird found to charge for protection:another way we are not unique = an avian protection racket
Nov. 19, 2010
Courtesy of BBSRC and World Science staff
In what some scientists are likening to a mob protection racket, a species of birds in Africa has been found to guard other birds from predators in exchange for food.
On one level, the security service offered by the drongo birds of the Kalahari Desert would seem to be legitimate. They do provide some true protection—unlike quite a few mafiosos, who create the very threat that for a fee they will supposedly ward off.
Yet there’s a hint of the criminal in the drongo operation too, scientists say. The avian guards help themselves to “payment” by occasionally screaming out false warnings of predators, then using the resulting confusion to snatch food from their feathered clients. Nor do the latter seem to specifically request protection; rather, the drongos are just—there.
The drawbacks notwithstanding, the “client” birds, pied babblers, gain something from the arrangement, according to scientists. That’s because the self-appointed sentinels, through their presence, allow the babblers to focus on foraging for insects rather than watching their backs.
The behavior may be a rare example of two species evolving from a parasitic to a “mutualistic” relationship, say the investigators, reporting the findings in the research journal Evolution.
“Drongos are parasitic birds who swoop in to steal food from other species,” explained Andrew Radford the Universities of Bristol, U.K., one of the researchers. Given this unsavory way of life, he went on, it was somewhat surprising to find that drongos perched above foraging babblers advertise their presence rather than keep a low profile.
They announce themselves “by issuing a call called a ‘twank’ every four or five seconds,” Radford said.
The explanation, he added, seems to be that the “twank” reassures babblers someone is keeping a lookout against predatory birds. This lets the babblers forage for insects more effectively. That, in turn, leads to better opportunities for the drongos to filch some of the catch. “When we played back these ‘twank’ calls to a babbler group, we found that they spread out over a larger area and lifted their heads less often, indicating that they were less fearful of predators when they thought a drongo was keeping watch,” Radford said.
But when the drongos cry wolf about the presence of predators, they scare other animals into dropping their catch, which the drongos then pounce on, said Radford and colleagues. So pied babblers have basically evolved to tolerate the drongos giving false warnings and stealing some of their hard-earned gains in exchange for the chance to forage in relative safety when a drongo is on duty.
Like a “good gangster,” Radford said, the drongos—not particularly large birds—provide real protection sometimes, both by making true alarm calls and by “mobbing” predators as a group.
But “despite all of the useful services drongos provide, the foraging birds are still more responsive to [alarm] calls from other babblers. It seems likely that the babblers simply don’t trust the drongo mafia as much as their own flesh and blood.”
The research could provide insight into other important mutualistic and parasitic relationships in nature, said Douglas Kell, chief executive of the U.K. Biotechnology and Biological Sciences Research Council, which funded the study. “Evolutionary arms races, including those between parasites and their hosts, and plants and animals and the diseases that they suffer, underlie a whole range of socially and economically important areas of biology,” he noted.
http://www.world-science.net/othernews/101119_racket.htm
Courtesy of BBSRC and World Science staff
In what some scientists are likening to a mob protection racket, a species of birds in Africa has been found to guard other birds from predators in exchange for food.
On one level, the security service offered by the drongo birds of the Kalahari Desert would seem to be legitimate. They do provide some true protection—unlike quite a few mafiosos, who create the very threat that for a fee they will supposedly ward off.
Yet there’s a hint of the criminal in the drongo operation too, scientists say. The avian guards help themselves to “payment” by occasionally screaming out false warnings of predators, then using the resulting confusion to snatch food from their feathered clients. Nor do the latter seem to specifically request protection; rather, the drongos are just—there.
The drawbacks notwithstanding, the “client” birds, pied babblers, gain something from the arrangement, according to scientists. That’s because the self-appointed sentinels, through their presence, allow the babblers to focus on foraging for insects rather than watching their backs.
The behavior may be a rare example of two species evolving from a parasitic to a “mutualistic” relationship, say the investigators, reporting the findings in the research journal Evolution.
“Drongos are parasitic birds who swoop in to steal food from other species,” explained Andrew Radford the Universities of Bristol, U.K., one of the researchers. Given this unsavory way of life, he went on, it was somewhat surprising to find that drongos perched above foraging babblers advertise their presence rather than keep a low profile.
They announce themselves “by issuing a call called a ‘twank’ every four or five seconds,” Radford said.
The explanation, he added, seems to be that the “twank” reassures babblers someone is keeping a lookout against predatory birds. This lets the babblers forage for insects more effectively. That, in turn, leads to better opportunities for the drongos to filch some of the catch. “When we played back these ‘twank’ calls to a babbler group, we found that they spread out over a larger area and lifted their heads less often, indicating that they were less fearful of predators when they thought a drongo was keeping watch,” Radford said.
But when the drongos cry wolf about the presence of predators, they scare other animals into dropping their catch, which the drongos then pounce on, said Radford and colleagues. So pied babblers have basically evolved to tolerate the drongos giving false warnings and stealing some of their hard-earned gains in exchange for the chance to forage in relative safety when a drongo is on duty.
Like a “good gangster,” Radford said, the drongos—not particularly large birds—provide real protection sometimes, both by making true alarm calls and by “mobbing” predators as a group.
But “despite all of the useful services drongos provide, the foraging birds are still more responsive to [alarm] calls from other babblers. It seems likely that the babblers simply don’t trust the drongo mafia as much as their own flesh and blood.”
The research could provide insight into other important mutualistic and parasitic relationships in nature, said Douglas Kell, chief executive of the U.K. Biotechnology and Biological Sciences Research Council, which funded the study. “Evolutionary arms races, including those between parasites and their hosts, and plants and animals and the diseases that they suffer, underlie a whole range of socially and economically important areas of biology,” he noted.
http://www.world-science.net/othernews/101119_racket.htm
Friday, November 5, 2010
Drongos mimic alarm calls to get a free lunch
African birds called drongos mimic other birds' alarm calls so that they can steal food from meerkats, scientists have found.
When a meerkat hears the alarm call, it drops its food and runs for cover thinking there's a predator around, allowing the drongo to get a free lunch.
When a meerkat hears the alarm call, it drops its food and runs for cover thinking there's a predator around, allowing the drongo to get a free lunch.
Fork tailed drongo (Dicrurus adsimilis)
This is the first time scientists have shown that birds use alarm calls specifically to deceive other species.
'Meerkats have learnt to recognise the alarm calls made by different bird species and flee for cover when they hear them,' says Tom Flower from the University of Cambridge and author of the study, which is published in Proceedings of the Royal Society B.
This latest study suggests that fork-tailed drongos (Dicrurus adsimilis) have exploited the meerkats, using both their own and mimicked alarm calls to scare meerkats when they see them with scorpions or geckos.
Flower was working on meerkats in the Kalahari in southern Africa, when he noticed drongos following them around. He noticed the birds making alarm calls when there were no predators nearby and thought they must be doing it on purpose.
'Drongos are following meerkats and pied-babblers around in the hope of catching their food,' says Flower.
He thought the birds might moderate the number of times they lied to avoid blowing their cover. But this doesn't seem to be the case. 'They just turn up and steal as much food as they can get away with,' Flower says.
The researchers think the birds use a repertoire of alarm calls to keep meerkats on their toes, and to stop the creatures getting suspicious.
'It's like the boy who cried wolf: if drongos use the same call each and every time, meerkats will learn to ignore them, so instead they use different calls,' says Flower.
'Meerkats have to sit up and take note, because they've got too much to lose if they ignore the calls. They could lose their lives,' he adds
Drongos act as sentries for other animals - when they make alarm calls, meerkats and birds called pied-babblers know to run for cover. But if they do it too often, they won't be believed. So, they have to change which alarm call they use to stop meerkats ignoring them.
While scientists know that birds use their own and other birds' alarm calls to alert others to danger, until now, they weren't sure if the calls were used to deceive.
To show that fork-tailed drongos use deceptive alarm calls to get a free lunch, Flower's research had to satisfy three conditions. He had to show that alarm calls are used only in a deceptive context rather than an aggressive context; that true alarm calls made by drongos and other species sound the same as false alarm calls; and that meerkats and pied-babblers run for cover in response to recordings of both false and true alarm calls.
Researchers have suggested a number of possible functions for mimicry, such as that being able to copy other birds might help attract a mate, or that it lets animals communicate with other species. But no-one has shown that having a wide repertoire of calls attracts more females.
Flower's research shows a clear function for vocal mimicry, when before scientists could only speculate. He thinks mimicry is likely to be a fairly simple mechanism, and that drongos work out which calls are most effective by trial and error.
He's now keen to go back to the Kalahari to see how drongos learn to vary their calls.
by Tamera Jones
http://planetearth.nerc.ac.uk/news/story.aspx?id=856
This is the first time scientists have shown that birds use alarm calls specifically to deceive other species.
'Meerkats have learnt to recognise the alarm calls made by different bird species and flee for cover when they hear them,' says Tom Flower from the University of Cambridge and author of the study, which is published in Proceedings of the Royal Society B.
This latest study suggests that fork-tailed drongos (Dicrurus adsimilis) have exploited the meerkats, using both their own and mimicked alarm calls to scare meerkats when they see them with scorpions or geckos.
Flower was working on meerkats in the Kalahari in southern Africa, when he noticed drongos following them around. He noticed the birds making alarm calls when there were no predators nearby and thought they must be doing it on purpose.
'Drongos are following meerkats and pied-babblers around in the hope of catching their food,' says Flower.
He thought the birds might moderate the number of times they lied to avoid blowing their cover. But this doesn't seem to be the case. 'They just turn up and steal as much food as they can get away with,' Flower says.
The researchers think the birds use a repertoire of alarm calls to keep meerkats on their toes, and to stop the creatures getting suspicious.
'It's like the boy who cried wolf: if drongos use the same call each and every time, meerkats will learn to ignore them, so instead they use different calls,' says Flower.
'Meerkats have to sit up and take note, because they've got too much to lose if they ignore the calls. They could lose their lives,' he adds
Drongos act as sentries for other animals - when they make alarm calls, meerkats and birds called pied-babblers know to run for cover. But if they do it too often, they won't be believed. So, they have to change which alarm call they use to stop meerkats ignoring them.
While scientists know that birds use their own and other birds' alarm calls to alert others to danger, until now, they weren't sure if the calls were used to deceive.
To show that fork-tailed drongos use deceptive alarm calls to get a free lunch, Flower's research had to satisfy three conditions. He had to show that alarm calls are used only in a deceptive context rather than an aggressive context; that true alarm calls made by drongos and other species sound the same as false alarm calls; and that meerkats and pied-babblers run for cover in response to recordings of both false and true alarm calls.
Researchers have suggested a number of possible functions for mimicry, such as that being able to copy other birds might help attract a mate, or that it lets animals communicate with other species. But no-one has shown that having a wide repertoire of calls attracts more females.
Flower's research shows a clear function for vocal mimicry, when before scientists could only speculate. He thinks mimicry is likely to be a fairly simple mechanism, and that drongos work out which calls are most effective by trial and error.
He's now keen to go back to the Kalahari to see how drongos learn to vary their calls.
by Tamera Jones
http://planetearth.nerc.ac.uk/news/story.aspx?id=856
Drongos mimic alarm calls to get a free lunch
African birds called drongos mimic other birds' alarm calls so that they can steal food from meerkats, scientists have found.
When a meerkat hears the alarm call, it drops its food and runs for cover thinking there's a predator around, allowing the drongo to get a free lunch.
When a meerkat hears the alarm call, it drops its food and runs for cover thinking there's a predator around, allowing the drongo to get a free lunch.
Fork tailed drongo (Dicrurus adsimilis)
This is the first time scientists have shown that birds use alarm calls specifically to deceive other species.
'Meerkats have learnt to recognise the alarm calls made by different bird species and flee for cover when they hear them,' says Tom Flower from the University of Cambridge and author of the study, which is published in Proceedings of the Royal Society B.
This latest study suggests that fork-tailed drongos (Dicrurus adsimilis) have exploited the meerkats, using both their own and mimicked alarm calls to scare meerkats when they see them with scorpions or geckos.
Flower was working on meerkats in the Kalahari in southern Africa, when he noticed drongos following them around. He noticed the birds making alarm calls when there were no predators nearby and thought they must be doing it on purpose.
'Drongos are following meerkats and pied-babblers around in the hope of catching their food,' says Flower.
He thought the birds might moderate the number of times they lied to avoid blowing their cover. But this doesn't seem to be the case. 'They just turn up and steal as much food as they can get away with,' Flower says.
The researchers think the birds use a repertoire of alarm calls to keep meerkats on their toes, and to stop the creatures getting suspicious.
'It's like the boy who cried wolf: if drongos use the same call each and every time, meerkats will learn to ignore them, so instead they use different calls,' says Flower.
'Meerkats have to sit up and take note, because they've got too much to lose if they ignore the calls. They could lose their lives,' he adds
Drongos act as sentries for other animals - when they make alarm calls, meerkats and birds called pied-babblers know to run for cover. But if they do it too often, they won't be believed. So, they have to change which alarm call they use to stop meerkats ignoring them.
While scientists know that birds use their own and other birds' alarm calls to alert others to danger, until now, they weren't sure if the calls were used to deceive.
To show that fork-tailed drongos use deceptive alarm calls to get a free lunch, Flower's research had to satisfy three conditions. He had to show that alarm calls are used only in a deceptive context rather than an aggressive context; that true alarm calls made by drongos and other species sound the same as false alarm calls; and that meerkats and pied-babblers run for cover in response to recordings of both false and true alarm calls.
Researchers have suggested a number of possible functions for mimicry, such as that being able to copy other birds might help attract a mate, or that it lets animals communicate with other species. But no-one has shown that having a wide repertoire of calls attracts more females.
Flower's research shows a clear function for vocal mimicry, when before scientists could only speculate. He thinks mimicry is likely to be a fairly simple mechanism, and that drongos work out which calls are most effective by trial and error.
He's now keen to go back to the Kalahari to see how drongos learn to vary their calls.
by Tamera Jones
http://planetearth.nerc.ac.uk/news/story.aspx?id=856
This is the first time scientists have shown that birds use alarm calls specifically to deceive other species.
'Meerkats have learnt to recognise the alarm calls made by different bird species and flee for cover when they hear them,' says Tom Flower from the University of Cambridge and author of the study, which is published in Proceedings of the Royal Society B.
This latest study suggests that fork-tailed drongos (Dicrurus adsimilis) have exploited the meerkats, using both their own and mimicked alarm calls to scare meerkats when they see them with scorpions or geckos.
Flower was working on meerkats in the Kalahari in southern Africa, when he noticed drongos following them around. He noticed the birds making alarm calls when there were no predators nearby and thought they must be doing it on purpose.
'Drongos are following meerkats and pied-babblers around in the hope of catching their food,' says Flower.
He thought the birds might moderate the number of times they lied to avoid blowing their cover. But this doesn't seem to be the case. 'They just turn up and steal as much food as they can get away with,' Flower says.
The researchers think the birds use a repertoire of alarm calls to keep meerkats on their toes, and to stop the creatures getting suspicious.
'It's like the boy who cried wolf: if drongos use the same call each and every time, meerkats will learn to ignore them, so instead they use different calls,' says Flower.
'Meerkats have to sit up and take note, because they've got too much to lose if they ignore the calls. They could lose their lives,' he adds
Drongos act as sentries for other animals - when they make alarm calls, meerkats and birds called pied-babblers know to run for cover. But if they do it too often, they won't be believed. So, they have to change which alarm call they use to stop meerkats ignoring them.
While scientists know that birds use their own and other birds' alarm calls to alert others to danger, until now, they weren't sure if the calls were used to deceive.
To show that fork-tailed drongos use deceptive alarm calls to get a free lunch, Flower's research had to satisfy three conditions. He had to show that alarm calls are used only in a deceptive context rather than an aggressive context; that true alarm calls made by drongos and other species sound the same as false alarm calls; and that meerkats and pied-babblers run for cover in response to recordings of both false and true alarm calls.
Researchers have suggested a number of possible functions for mimicry, such as that being able to copy other birds might help attract a mate, or that it lets animals communicate with other species. But no-one has shown that having a wide repertoire of calls attracts more females.
Flower's research shows a clear function for vocal mimicry, when before scientists could only speculate. He thinks mimicry is likely to be a fairly simple mechanism, and that drongos work out which calls are most effective by trial and error.
He's now keen to go back to the Kalahari to see how drongos learn to vary their calls.
by Tamera Jones
http://planetearth.nerc.ac.uk/news/story.aspx?id=856
Subscribe to:
Posts (Atom)