Tag: Birds (pet; ornamental; prey e.g. falcons)

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Bird extinctions worse than thought

When scientists try to gauge the impact of humans on bird populations since 1500–the time Europeans began to explore the world in earnest–they often cite estimates that, on average, one species has gone extinct every 4 years. Now, a group of researchers says that figure may be far too low. The good news is that conservation efforts in the 20th century have prevented many extinctions, but the authors warn that continued destruction of habitat makes even more birds likely to vanish forever in the next 100 years. Not just birders love lists. For their research, ecologist Stuart Pimm of Duke University in Durham, North Carolina, and colleagues constructed and analyzed a massive list of all species of birds and when they were first described. They came up with 9975 species alive today and 154 species that either have gone extinct or have been missing so long that they are likely gone. Most estimates of extinctions rates simply divide rough estimates of these two numbers. This approach yields a rate of 31 extinctions per million species per year (or 1.2 species every 4 years).

The problem, Pimm points out, is that the list of extinctions is incomplete. There are likely many species that went extinct before they were ever discovered; the bulk of taxonomic work by ornithologists happened in the 19th century, long after Europeans began to destroy habitat, let loose invasive species, and otherwise doom vulnerable species of birds. (Indigenous peoples such as the Polynesians also took a toll on birds before 1500, Pimm points out). By considering how long taxonomists have known about birds, Pimm and his colleagues were able to take these untold extinctions into account. The average rate since 1500 turned out to be 85 extinctions per million species per year (or 3.4 species every 4 years).

Conservation efforts have made an impact, the authors argue. Since 1975, 20 species of birds have gone extinct. Without conservation, however, another 25 species, such as the California Condor, would likely have vanished–and the extinction rate would have jumped to 150 extinctions per million species a year, the team reports online this week in the Proceedings of the National Academy of Sciences. Yet the situation could get far worse than that. As available habitat shrinks by 50%, the number of species declines by 15%. Assuming that the area of now-pristine habitats is halved–as it was in eastern North America by 1870–Pimm’s group calculates that some 1500 species will likely go extinct over the next century. Climate change could darken the scenario even further. “The scary thing is that we’re investing a lot in conservation, but it’s reasonable to expect extinction rate to increase,” says Gregory Butcher, director of bird conservation at the National Audubon Society in Washington, D.C. He adds that the situation is worse for other groups because they are not as well studied or protected as birds.

ScienceNow
July 18, 2006

Original web page at ScienceNow

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Wild bird role in flu ‘unclear’

The role of swans and other wild birds in spreading bird flu is still unclear and uncertain, according to scientists. Many of the assumptions being made about the part played in the spread of the disease by wild birds simply do not stand up to analysis, they say. International researchers are in Rome for a two-day conference to discuss the spread of avian flu. The scientific meeting has been organised by the Food and Agriculture Organization (FAO) of the UN and the World Animal Health Organization (OIE).

Dr Ian Brown, from the Veterinary Laboratories Agency (VLA) at Weybridge in Surrey, UK, told the BBC News website: “We shouldn’t just assume that it’s a few species of ducks and the swans that are the risk species. Certainly, we have to look at those, but we need to keep a broad open mind on this one.” Dr Brown said that swans were interesting indicators of the presence of the disease, but their role in spreading it was less clear. This is something we may have here for many years and we may have to live with it.

Dr Domenech, FAO, said: “We have to be careful that just because we see dead swans and we find the virus in them that they’re the answer to why the virus is spreading,” he said. “We do know that swans are largely immobile; they don’t migrate over large distances on the whole. “The movements that have happened in Europe in the past six months have been because of bad weather; so we have to be careful that all the explanations of how the virus is spreading are not placed at the swans’ door. They’re one part of a complicated web.” The scientists also heard an impassioned plea for the use of vaccines to control the disease in domestic poultry.

Dr Robert Webster, from St Jude’s Children’s Research Hospital in Memphis, Tennessee, US, said that it was absurd that vaccines were not used. “The global poultry industry is the main spreader of H5N1, but migratory birds have certainly played a role. A main issue in my mind is the use of vaccines at agricultural level to control this thing,” he said. “There are good vaccines available; it can be controlled at source, but the agricultural authorities of the world won’t standardise their vaccines for antigen content. They say it can’t be done, but it’s not true; it can be done.” Dr Webster said that using vaccines was of far greater importance in the developing world. “The wealthy countries can afford to cull their infected birds; the poorer simply can’t. The science allows us to make superb vaccines for poultry – let’s use them for God’s sake.”

There were also calls for a greater focus on Africa. According to the chief veterinary officer of the FAO, Dr Joseph Domenech, if the disease becomes endemic on the continent, it could re-infect the rest of the world for years to come. Dr Domenech said in Africa, “we have a risk of permanent endemicity, we have a risk of new countries being contaminated, and there is a danger of permanent re-infection of other regions through wild birds or trade. In other countries, the efforts are already done; but not in Africa”. Eight African countries have reported outbreaks of bird flu to date but experts speaking here expect that number to rise.

Scientists are questioning if African countries have the economic or political capacity to eradicate the virus. There are worries about the difficulties in enforcing culling and the control of poultry movements, and there are simply not enough staff to carry out adequate monitoring. According to Dr Domenech, Asia and Europe had made progress in the speed of their detection and response. This was the key to dealing with new outbreaks, he said. “Even if there are reservoirs of infection in the world that you can do nothing about, with effective monitoring and response you can control it,” he added. “This is something we may have here for many years and we may have to live with it.” Many delegates spoke of the need for better information to help target their research. There is a growing understanding that while there is excellent research being done on the ground with wild birds, there is a lack of a global perspective.

BBC News
June 20, 2006

Original web page at BBC News

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Pigeon-brained birds can think in logarithms

There are asymmetries in the way animals perceive numbers and time, and a recent experiment showed that pigeons underestimate the midpoint between two time intervals. In the experiment, pigeons were trained to tap one lever when a light flash was “short”, perhaps 1 second long, and another lever when the flash was “long”, say 16 seconds. When the birds then saw flashes of intermediate length, you would expect them to distinguish long from short around the mid-point of 8 or 9 seconds. But instead they switched at 4 seconds.

Pigeons might perceive time on a logarithmic scale on which higher values are increasingly compressed together. Alternatively, they might perceive time linearly but are confused by longer intervals. If pigeons use a log scale, they will correctly classify 9 and 10-second flashes more often than 7 and 8-second flashes, while if they use a linear model their accuracy should be similar. William Roberts from the University of Western Ontario in London, Canada, has now shown that six pigeons, tapping levers for 20 days, conformed neatly to the logarithmic model (Behavioural Processes, vol 72, p 207). The results may apply to humans, because brains have to prioritise the small numbers most relevant in life. It might be an evolutionary strategy to discriminate numbers like this, says Roberts.

New Scientist
June 6, 2006

Original web page at New Scientist

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India bans drug threatening to wipe out vultures

India has banned the production and sale of an anti-inflammatory drug used in cattle that is poisoning the country’s vultures one step up the food chain. Vultures fulfill a vital role, stripping down animal carcasses that would otherwise slowly rot and attract disease-spreading feral dogs and vermin. But the number of South Asia’s Oriental white-backed, long-billed and slender-billed vultures has plummeted more than 97 percent over 15 years, which scientists say is largely due to the widespread use of the drug diclofenac in cattle, which causes fatal liver damage in vultures.

Now, India has ordered drug companies to stop making and marketing diclofenac for veterinary use within three months. “This ban is exceptionally good news and the crucial step we have all been looking for,” said Chris Bowden, head of the Asian Vulture Program at Britain’s Royal Society for the Protection of Birds, in a statement. “The decline of vultures has been quicker than any other wild bird including the dodo — and we know what happened to them.”

India is recommending farmers and vets use the drug meloxicam instead. A study published in the journal PLoS Biology in January said meloxicam was just as effective in cattle without being toxic to vultures, even in high doses. But without an outright ban on diclofenac, conservationists are worried imported supplies will be used.

Reuters
June 6, 2006

Original web page at Reuters

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Birds grasp basic rule of grammar, study finds

The European starling—long known as a virtuoso songbird and expert mimic—may also soon win a reputation as something of a grammatician, researchers say: the little bird can learn language patterns formerly thought to be unique to humans. Researchers led by Timothy Q. Gentner, a psychologist at the University of California, San Diego, have found that starlings can understand a key feature of grammar. This feature, called recursive center-embedding, is what lets speakers make new sentences by inserting words and clauses within other sentences.

Thus, for example, “Oedipus ruled Thebes” can become “Oedipus, who killed his father, ruled Thebes” or “Oedipus, who killed his father, whom he met on the road from Delphi, ruled Thebes.” This can theoretically go on without limit. Some researchers, including followers of the highly influential U.S. linguist Noam Chomsky, have held that this is a universal feature of human language, unique to humans, and which forms the logical core of our language. The new findings challenge that view, Gentner said. “If birds can learn these patterning rules, then their use does not explain the uniqueness of human language.”

The finding also “re-invigorates the search” for the evolutionary roots of language among animals, said Daniel Margoliash, a coauthor along with Gentner of a paper describing the findings. The study appears in the April 27 issue of the research journal Nature. The scientists created artificial starling songs that followed two different rules. One allowed a sound to be inserted in the middle of a series of sounds, the simplest form of recursive center-embedding. The other allowed for sounds to be added only at the beginning or end of a string.

The researchers used recordings of eight different “warbles” and eight different “rattles” produced by the same male starling to build 16 songs. Eight of these followed the first patterning rule, and eight the second. They then taught 11 adult birds to distinguish the two sets of songs. The birds received a food reward for pecking at a button when they heard songs from the first group, and for not pecking when they heard songs from the second set. Nine starlings eventually learned to distinguish the patterns, although it took months and a few tens of thousands of trials, the researchers reported.

When tested with different combinations of rattles and warbles that followed the same rules, the starlings performed well above “chance” levels, the researchers said. That suggests the birds had learned the abstract patterns and not just memorized specific songs, they added. The researchers also checked whether the birds responded to “ungrammatical” strings, that violated the established rules. The starlings treated these differently, they reported.

The experimenters then studied whether the birds could grasp a key feature of human grammars: Could they extrapolate these rules to distinguish among longer strings of sounds? Remarkably, Gentner said, they could. The finding that starlings can grasp even simple grammatical rules, Gentner said, suggests humans and other animals share pattern recognition skills and possibly other cognitive abilities. “There might be no single property or processing capacity,” the researchers wrote, “that marks the many ways in which the complexity and detail of human language differs from non-human communication systems.” More generally, Gentner said, “The more closely we understand what nonhuman animals are capable of, the richer our world becomes. Fifty years ago, it was taboo to even talk about animal cognition,” he continued. Now, “no one doubts that animals have complex and vibrant mental lives.”

World Science
May 23, 2006

Original web page at World Science

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Males with elevated levels of testosterone lead shorter lives but have more success siring offspring

Comparative studies have studied testosterone levels and related them to mating systems and aggression, but very few studies have attempted to relate testosterone to fitness, that is, the combination of lifetime reproductive success and survival, in the wild or experimentally. Over nine breeding seasons, Wendy Reed (North Dakota State University) and her colleagues followed a group of dark-eyed juncos, small mountain songbirds found throughout North America. They injected males with elevated levels of testosterone and found that they had shorter lives but that they were very successful at siring more offspring — even with females who were mated with other males. “The surprising result was that testosterone-treated males had a higher overall fitness than control males,” write the authors in a study in the May issue of American Naturalist.

This led to the question of why don’t juncos naturally have higher levels of testosterone? Testosterone-treated males produced more offspring, but they were smaller, and smaller offspring had lower postfledging survival. Older, more experienced females preferred to mate with older males and realized higher reproductive success when they did so. While young males treated with testosterone increased their ability to attract older females, it resulted in poor reproductive performance. “Although testosterone increased male fitness, as measured by lifespan and number of offspring, the extended effects on offspring and female mates were generally negative and may ultimately constrain the evolution of higher testosterone levels in males,” conclude the authors.

Science Daily
May 9, 2006

Original web page at Science Daily

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A swan found dead in Fife, Scotland, died of the deadly H5N1 strain of bird flu

Experts at an earlier press briefing in London said that other wild birds are almost certain to be infected, and warned poultry farmers to keep their birds indoors if possible to avoid contact with wild birds. The confirmation establishes that the virus continues its westward march after originating in the Far East. Already, it has been reported in 13 European countries. Tests by the UK government’s Veterinary Laboratories Agency established that the swan tested positive for H5N1, the highly pathogenic form of bird flu which has officially claimed 103 human lives so far. UK government officials are already undertaking an urgent assessment to decide what measures are needed to stop the virus spreading to the country’s poultry. “However, on the basis of a preliminary risk assessment, it has been concluded that a Britain-wide poultry housing requirement would be disproportionate,” said a joint statement from the UK and Scottish Chief Veterinary Officers.

Poultry have already been forcibly housed within 3 kilometres of the village where the swan was found. Surveillance has been introduced within 10-kilometres. The Scottish Executive is considering whether to extend these measures. The experts meeting in London warned that other birds are probably infected. “We don’t know if this is the first and only bird infected, or the twenty-first,” said Bob McCracken, past president of the British Veterinary Association. “An infected bird will be producing millions of virus particles in its droppings, which can be picked up by other birds, and we should work on the assumption that that’s already happened,” he said. According to McCracken, it is likely that there is a small pool of birds in the Fife area carrying the virus. “We don’t know which bird brought it to Fife, but it’s irrelevant,” said McCracken. “Let’s make sure that as we move forward now, we minimise the risk to domestic poultry.”

McCracken said that his advice to poultry farmers, and that of the BVA, would be to move birds indoors as soon as possible, before it becomes mandatory. “We’re moving closer to the day when moving birds indoors will be necessary.” Such measures are necessary to stop poultry and their food being infected by droppings from infected wild birds. This is far more important than vaccination of birds, he says. “Vaccination’s a tool we in the BVA think should remain on the table. It may follow later, but not now.” Nor is there any scientific justification for keeping cats and dogs indoors, he said, despite a report this week in Nature highlighting the issue of bird flu reaching cats.

Experts also calmed fears that there was an imminent threat to human health. “For more than two years we’ve been monitoring the spread of these viruses in East Asian countries, and against the background of 5000 outbreaks in birds there have been only 200 cases of human infection,” said Alan Hay, the director of the UK Medical Research Council’s World Influenza Centre. “What makes us alarmed is that more than half of these cases have been fatal, but at the present time, it’s very difficult to contract an infection,” said Hay. “Most cases can be put down to very close contact with infected poultry,” he said. “The main risk is if this virus becomes part of a pandemic where it becomes virulent,” said Jim Robertson of the National Institutes for Biological Standards and Control. “But that risk doesn’t change by it being in the UK.”

New Scientist
April 25, 2006

Original web page at New Scientist

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Restoring wetlands key to curbing bird flu: report

Restoring wetlands and clearing poultry farms from migratory flyways could help curb the spread of bird flu by stopping wild birds from mixing with domestic fowl, a U.N.-commissioned report said. The clearance of wetlands due to drainage for agriculture or hydroelectric projects is forcing some wild birds on to alternative sites such as farm ponds and paddy fields, bringing them into direct contact with domestic poultry, the report said. This increases the spread of the virus, which has jumped from Asia to Europe, the Middle East and Africa. “There’s a contraction for the habitat for wild birds and a natural situation arising which promotes the inter-mixing of wild birds and domestic poultry,” said David Rapport, a Canadian professor and lead author of the report.

“So should a pathogen arise in domestic poultry, it becomes more likely to be spread into wild birds… because the health of those ecosystems has been compromised,” he told a news conference in Nairobi. Wild birds are believed to have played a role in the spread of the H5N1 virus into more than 45 countries. Bird flu can infect people who come into close contact with infected poultry. Since 2003, more than 100 people have died after being infected with the virus, most of them in Asia. Scientists fear the disease could mutate into a form that could pass easily between humans, causing a pandemic in which millions could die. The report, presented at a United Nations Environment Programme (UNEP) seminar on bird flu, called for poultry and people to be kept apart, even though it acknowledged such plans would meet resistance in some parts of the world.

In Asia and Africa, people often live alongside their chickens and other domestic animals. “As unpalatable as this may be, where it is clearly in the interest of preventing future pandemics with potentially catastrophic global effects, it can and should be undertaken,” said Rapport, who is from the University of Western Ontario.
Experts, who met at the UNEP bird flu seminar in the Kenyan capital, said that all countries needed to undertake risk assessment and that national veterinary services should meet certain minimum standards. The experts also highlighted the need to compensate poor farmers for culling poultry. Weak veterinary services, few hospitals, lack of health education, poor communications and the prevalence of a host of other deadly diseases all mitigate against rapid detection of any cases of bird flu in Africa, the world’s poorest continent.

Reuters
April 25, 2006

Original web page at Reuters

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Bird flu hides deep in the lungs

This week, two research groups are independently reporting results that help explain why the H5N1 avian influenza virus is so lethal to humans but so difficult to spread. Unlike human influenza viruses, the teams report, H5N1 preferentially infects cells in the lower respiratory tract. Residing deep in the airways, the virus is not easily expelled by coughing and sneezing, the usual route of spread. The results “explain a lot of the mysteries” surrounding H5N1, says K. Y. Yuen, a virologist at the University of Hong Kong. A better understanding of the virus couldn’t be more timely. Endemic in much of Asia, H5N1 has recently spread through Europe and to Africa (ScienceNOW, 9 February). It has killed 98 of the 177 humans it has infected. Flu experts worry that if the virus mutates into a form that could be easily passed among humans, it could spark a pandemic. The two reports, which used different strategies but reached the same conclusion, suggest just what sort of mutation would be needed.

One team, led by Yoshihiro Kawaoka of the University of Wisconsin, Madison, tested various tissues of the human respiratory tract for receptors to which the virus can bind. Human flu viruses preferentially bind to what are known as a 2,6 galactose receptors, which populate the human respiratory tract from the nose to the lungs. Avian viruses prefer a 2,3 galactose receptors, which are common in birds but were thought to be nearly absent in humans. Using marker molecules that bind to one receptor or the other, the team found that humans also have a 2,3 galactose receptors, but only in and around the alveoli, structures deep in the lungs where oxygen is passed to the blood. They describe their findings in the 23 March issue of Nature.

The second team, led by pathologist Thijs Kuiken of Erasmus University in Rotterdam, the Netherlands, used a more direct technique to show that H5N1 readily binds to alveoli but not to tissues higher up in the respiratory tract. Kuiken, whose team will publish its findings online tomorrow in Science, notes that this pattern is consistent with autopsies that have shown heavy damage to the lungs but little involvement of the upper respiratory tract. Among experimental animals, the team reports, cats and ferrets more closely match the human pattern of infection than do mice and macaques. “This is an important factor to consider when planning experiments” to understand the pathology of H5N1, says Kuiken.

Yuen notes that the findings also explain clinical anomalies such as why nasal swabs of H5N1 patients are less reliable than throat swabs in detecting the virus. And they suggest that clinicians need to exercise particular care when performing procedures, such as intubation, that might give the virus a route out of a patient’s lungs. The risk of a pandemic would ratchet up substantially should the virus acquire the ability to bind to receptors in the upper respiratory tract, Kuiken warns. But just how difficult that mutation is to acquire “is something this research did not address,” he says.

Science Magazine
April 11, 2006

Original web page at Science Magazine

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Pigeons get backpacks for air pollution monitoring

A flock of pigeons fitted with mobile phone backpacks is to be used to monitor air pollution, New Scientist magazine reported on Wednesday. The 20 pigeons will be released into the skies over San Jose, California, in August. Each bird will carry a GPS satellite tracking receiver, air pollution sensors and a basic mobile phone. Text messages on air quality will be beamed back in real time to a special pigeon “blog”, a journal accessible on the Internet. Miniature cameras slung around the pigeons’ necks will also post aerial pictures.

The idea is the brainchild of researcher Beatriz da Costa, of the University of California at Irvine, and two of her students. They have built a prototype of the pigeons’ equipment, containing a mobile phone circuit board with SIM card and communication chips, a GPS receiver, and sensors capable of detecting carbon monoxide and nitrogen dioxide. “We are combining an air pollution sensor with a home-made cellphone,” da Costa told New Scientist. The team is planning to squeeze all the components onto a single board small enough for the birds to carry in a backpack, New Scientist said. The pigeons will take to the air at the inter-Society for Electronic Arts’ annual symposium in San Jose on August 5. The data they send back will be displayed on the blog in the form of an interactive map.

Reuters
February 14, 2006

Original web page at Reuters

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Are sea birds becoming too dumb to survive?

The global decline in seabird populations is of growing concern to ecologists, and now researchers have discovered a new cause – some may be becoming too stupid to survive. Climate change may be the root of the trouble. New environmental conditions lead fish to migrate, leaving the birds that feed on them malnourished. The new research shows that lack of a specific nutrient in red-legged kittiwakes damages their cognitive abilities and could leave them too daft to find food.

The sharp drop in the seabird numbers coincided with a climate shift that resulted in a reduced abundance of lipid-rich fish in the area, though other fish species remained available as food. The researchers theorised that chicks born at or after this time lacked the lipid-rich foods they needed for proper cognitive development, leaving them less likely to have the skills needed to survive as independent adults.

So Kitayski’s team set up an experiment with 20 kittiwake chicks from the Pribilof Islands that were hatched in captivity. For the first 14 days after hatching, all the chicks were fed a high lipid diet corresponding to adequate parental feeding. After that and until the age of 47 days – the average fledgling age – half the chicks were switched to a low-lipid diet of rainbow smelt, while the other 10 received lipid-rich silverside fish. During this time, the birds were given multivitamins and mineral supplements to ensure that lipids were the only nutrients being varied. Then for a final 10 days, all the kittiwakes were fed silverside.

The birds’ cognitive abilities were then tested with a series of learning tasks, such as discovering the link between the colour of a dish and the presence of food. Those raised on a poor lipid diet could not learn tasks that birds raised on lipid-rich diets learned almost to perfection. Such learning skills are believed to be important in finding food. “This is really fascinating research, and demonstrates a very complex mechanism driving a reduction in population,” says Mark Grantham, at the British Trust for Ornithology. “Climate change has had a noticeable effect on both the timing and success of breeding of many of our bird species, but this new study just shows how unpredictable such consequences can be.”

Norman Ratcliffe, seabird biologist for the UK’s Royal Society for the Protection of Bird, agrees that the experiment shows chick nutrition affects the ability of birds to find food after they fledge. But he says it remains unclear if this is the cause of the red-legged kittiwake decline: “The chicks fed poor quality diets are lighter as well as cognitively impaired and this could also contribute to their chances of post-fledging survival.” Weekly blood tests performed during the study also showed that the birds on the low-lipid diet had elevated levels of the stress hormone corticosterone. “Malnutrition imposed early in life is known to alter morphological, neuro-physical and functional aspects of the developing brain, which might affect learning and memory formation in mammals,” the researchers write. “A chronic elevation of corticosterone may also cause atrophy of the hippocampal processes and neuron loss in mammals.”

“This work may have implications for many migratory species that will have to deal with an increasingly changing environment and will need to be able to adapt rapidly,” Grantham told New Scientist. “It has been shown recently that brain size effects behaviour and can even influence population trends, so it would be expected that an increase in stupidity in some species would adversely affect their ability to perform their day-to-day activities.”

New Scientist
December 6, 2005

Original web page at New Scientist

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Bird flu knocks on Europe’s door

Chief veterinary officials from the European Union’s 25 member states met in Brussels on Thursday to discuss what to do if wild birds carrying H5N1 bird flu bring it to Europe from Russia. But they concluded it is not clear whether wild birds are spreading the virus in Russia, nor how likely it is that birds migrating into Europe could be carrying it.

H5N1 bird flu has been identified in backyard poultry in the Novosibirsk region of Russia, where an outbreak started in late July. DNA sequence information from samples near Novosibirsk shows it is highly similar to the virus that killed thousands of wild birds at Qinghai Lake in China in May 2005. Russia has also reported outbreaks involving H5 bird flu in backyard poultry in its Altai Kray, Tyuman, Omsk, Kurgan and Cheyabinsk regions, which cover a band of territory parallel to the northern border of Kazakhstan.
H5N1 flu has also been confirmed in Kazakhstan. It is not clear how similar any of these latter viruses are to the Qinghai H5N1 or others that have circulated in east Asia and caused 57 human deaths so far.

But whether this spread is likely to continue into Europe depends on whether it is being carried by healthy migrating birds. If instead the virus is being spread by trade in infected poultry, as it has been in south-east Asia, the picture would be different. And the infections reported so far do coincide geographically with major rail, trade and travel links through the region. Evidence for spread by wild birds is circumstantial. Yevgeny Nepoklonov, head of the veterinary department of the Russian Agriculture Ministry, told the World Animal Health Organisation (OIE) in Paris this month that in the six territories where outbreaks have been reported, “the first [domestic] birds to be affected are those kept in homes close to reservoirs” – where wild birds may visit.

On the other hand, not one healthy wild bird carrying highly pathogenic H5N1 has yet been reported, apart from a few carrying a somewhat different virus in Hong Kong in 2002. Hon Ip, a virologist at the US National Wildlife Health Center in Madison, Wisconsin, US, notes that in Russia’s report on Novosibirsk to the OIE, the H5N1 virus it had isolated from a wild duck was different from the viruses isolated in its domestic poultry. “No data that shows the wild birds were the vector of transmission has been made available at the present time,” Ip commented on ProMED-Mail, an internet bulletin board on emerging disease. “The same pattern of spread can just as easily be seen as from the major routes of human transportation.”

Adding to uncertainties, an investigation of an outbreak of bird flu on remote lakes in Mongolia by the Wildlife Conservation Society in August found that only 100 birds of more than 6000 on the lake died, suggesting either that the virus does not infect many birds in wild flocks, or the majority of birds that caught the virus remained healthy carriers. If wild birds are carrying H5N1, say European veterinary experts, the key to preventing outbreaks will be to prevent contact between poultry and wild birds. Free-range chickens have already been moved under cover in the Netherlands, which has had major outbreaks of other kinds of bird flu recently. But the vets in Brussels recommended that EU countries: hold their fire, increase their monitoring of flu viruses in wild birds, be ready to destroy infected birds, bring free-range animals inside if the virus is detected. They recommended that in at-risk situations poultry vaccination might be considered as a risk-mitigating measure.

New Scientist
September 13, 2005

Original web page at New Scientist

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Bird samples from Mongolia confirmed as H5N1 avian flu

The United States Department of Agriculture (USDA) has positively identified the pathogenic form of avian flu–H5N1–in samples taken from birds last week in Mongolia by field veterinarians from the Wildlife Conservation Society (WCS). It is the first instance of this viral strain occurring in wild migratory birds with no apparent contact to domestic poultry or waterfowl.

Recent reports of influenza outbreaks in wild birds in China and Russia have failed to put die-offs in perspective with the numbers of unaffected birds, thus there was no way to assess the impact. The WCS team at Erkhel Lake in Mongolia collected this information for the first time. Overall, over 6,500 apparently healthy birds of 55 species were observed on the lake. The percentage of sick or dead birds was miniscule according to Gilbert following the survey, suggesting that either the virus had little effect on the birds or that very few were actually infected by the bug. Early results suggest that it may be the latter.

Whereas prior outbreaks in wild birds have happened either in close proximity to infected domestic poultry and waterfowl, or in regions where such contact could not be excluded, Mongolia’s paucity of domestic poultry suggests a new vector of avian flu. Finding the H5N1 strain during this expedition suggests that while the highly pathogenic avian influenza can be carried across long distances, the waterfowl species typically identified in recent outbreaks appear to be victims rather than effective carriers of the disease.

The multidisciplinary, collaborative response to this latest outbreak reflects the WCS One World-One Health approach to making informed, multidisciplinary decisions on global health crises that intersect human, wildlife, and livestock health. WCS experts are warning that to contain this potential epidemic, prevention activities must include better management practices in farms, especially those that are small and open-air, where domestic poultry and waterfowl are allowed to intermingle with wild birds. Officials would also need to monitor wildlife markets, where wild and domesticated species are kept in close proximity, and risk exposure to a wide range of pathogens.

Wildlife and health experts, including the F.A.O., maintain that indiscriminate culling of wild migratory bird populations would be ineffective in preventing the spread of avian flu. “Focusing our limited resources on the hubs and activities where humans, livestock, and wildlife come into close contact,” says Dr. William Karesh, Director of WCS’s Field Veterinary Program, who lead the WCS team in Mongolia, “is the best hope for successfully preventing the spread of avian flu and protecting both people and animals.”

Science Daily
September 13, 2005

Original web page at Science Daily

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Bird flu may soon land in Europe and Australia

Thousands of wild birds in north-west China may have been infected by a bird flu virus closely related to the one that has devastated poultry farms in south-east Asia. The birds might carry the virus as far as India, Australia and Europe. That is the warning from two teams of scientists in China. They report in Nature and Science this week that a massive die-off of birds at Qinghai Lake in north-west China, a major summering spot for migratory waterfowl, is due to H5N1.

Officially, 6000 birds had died by 1 July. But far more may have been affected, says George Gao, of the Chinese Academy of Sciences, and the leader of one of the teams. Tens of thousands of migrating water birds summer at the lake, says Taej Mundkur in Pune, India, an expert on the region’s birds with the international conservation group Wetlands International. In mid-August, the survivors will start returning to their winter ranges, which stretch from eastern Europe to Australia and Alaska, and overlap with the ranges of other migrants. Mundkur cautions that it is not known how many birds from Qinghai Lake migrate to the farthest reaches of their species’s known ranges. But if some birds carrying the virus remain healthy enough to migrate, the disease could spread far and wide.

So far no testing has been done to see if this is likely. “We have had no chance to sample healthy migratory birds by Qinghai Lake,” says Yi Guan at Shantou University Medical College in Guangdong province, who led the other team. The Chinese ministry of agriculture is reportedly planning to investigate later in July, but neither Gao nor Guan has received permission to study healthy birds. The RNA sequence of the Qinghai virus reveals that three of its eight genes are almost identical to those of a virus isolated from a chicken in Shantou in 2003. The other five genes resemble those of viruses found in southern China earlier in 2005, which belong to the “Z genotype” virus circulating across east Asia.

This means the Qinghai virus was not, as first claimed by officials, brought into China from other countries by migrating birds. The bird that started the outbreak might have picked up the virus in southern China or from poultry closer to Qinghai, say Guan and Gao. What is not clear is whether the Qinghai virus is any more deadly to wild birds than the other H5N1 variants that have killed wild birds. The Qinghai outbreak might merely be the first time that H5N1 has had the opportunity to infect such a large number of wild fowl. “Any susceptible migrant could pick up the virus and die in the wild without being noticed,” says Mundkur. “It is only because the birds were congregating in a place that is visited, that the mass die-off was reported at Qinghai.” Nor is it known if the Qinghai virus could kill humans. It does have a mutation associated with increased deadliness in mammals – Gao found that it kills all mice infected with it in four days – but this mutation may not be enough to make the virus dangerous for humans.

What is certain is that if the virus spreads to other countries, it will decimate poultry industries. The sequence also shows that H5N1 viruses in Asia are swapping genes – which could give rise to a virus capable of causing a human pandemic.

New Scientist
August 2, 2005

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The non-migratory blackbird has a large brain and has been seen to forage for food with a stick

It takes brains to make it through the winter, at least if you’re a bird. A new survey suggests that bird species that have evolved to fly south for the coldest months tend to be those that weren’t smart enough to survive if they stayed put. The study shows that migratory birds, which leave temperate regions in search of warmer climes when temperatures start to dip, have smaller brains than those who stay behind. Non-migrating species also show more creativity when it comes to finding a meal in the frugal winter months. Daniel Sol of the Independent University of Barcelona in Spain and his colleagues used previous observations of 134 bird species in Europe, Scandinavia and western Russia. They collected data on brain size, and also counted the number of times researchers had spotted the birds adopting a novel feeding technique.

Species that remain resident during the winter have adopted more feeding innovations, the team reports in a paper published online by Proceedings of the Royal Society. The blackbird, Turdus merula, for example, has been seen using twigs to clear snow away while foraging. And the bullfinch, Pyrrhula pyrrhula, has been spotted tearing flesh from chicken and duck carcasses to get a meal. On average, non-migratory birds have been spotted using four novel feeding styles per species, compared with around three for short-distance migrants, and just over one for species that commute beyond the Sahara Desert to the south. “Species with greater foraging flexibility seem to be able to cope with seasonal environments better, while less flexible species are forced to become migratory,” say Sol and his team. A similar pattern was seen in brain size, with the resident species tending to have more upstairs than short-distance migrants, who in turn had larger brains than the long-distance fliers.

Brain tissue requires a lot of energy, the researchers say. So migratory birds, which expend a large chunk of their energy commuting, may benefit from having smaller brains to maintain. But, the team argues, small brains probably forced the birds to adopt a migratory lifestyle in the first place, because they were not smart enough to cope with winter. Their lack of inventiveness may mean that migratory species will have more trouble adapting to future changes in environmental conditions, Sol and his colleagues add. With climate change and human intervention changing the landscape, these birds may be at greater risk of extinction than those that stay put.

Nature
July 19, 2005

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DNA from feathers tells tale of eagle fidelity

A trail of feathers led a team of Purdue University scientists to confirm that eagles from central Asia are quite possibly the most faithful of birds. By performing DNA analysis on the feathers left behind at nesting sites, the researchers were able to identify individual Eastern imperial eagles in a nature reserve in Kazakhstan. Their analysis showed that not one adult strayed from its mate – a degree of fidelity highly unusual among birds, the vast majority of which mate with and raise offspring from multiple partners.

Not only is this study the first to confirm monogamy in eagles, more importantly, it also is the first to rely on feathers collected “noninvasively,” or without trapping and handling, to provide a source of DNA to determine relationships among individuals and determine various population parameters. “That we were able to use feathers we collected noninvasively as a source of DNA is the number one thing scientists will be interested in,” said Andrew DeWoody, associate professor of genetics and senior author of the study, which was published online Friday (July 1) in the journal Molecular Ecology. “People have been doing studies like this for several years with mammals, but this is a first for birds.” By developing a protocol for extracting DNA from feathers, the researchers also have added another tool to help conservation biologists study rare and elusive birds of prey.

The researchers used a technique called DNA fingerprinting to help them genetically “tag” individuals in the population without capture, said Jamie Rudnick, the paper’s first author and a graduate student who conducted the study as part of her doctoral thesis. “Collecting feathers at the nest site helped us determine population parameters we wouldn’t have been able to otherwise,” she said. Those parameters, such as yearly survival rates and ratios of males to females, help conservation biologists monitor populations of rare or endangered species. Noninvasive sampling allows biologists to track changes in populations over time without the risks associated with handling live animals, she said. “Eastern imperial eagles are hard to catch, and individuals are difficult to tell apart,” Rudnick said. “By performing genetic analysis on feathers collected at the site, we were able to track the presence or absence of individual birds over a six-year period.”

This kind of monitoring is essential to conserving rare or endangered species, said Todd Katzner, director of conservation and field research at the National Aviary in Pittsburgh and a study co-author. “You can’t conserve a population unless you know how big it is and whether it’s growing or shrinking,” Katzner said. “This approach allows us to monitor wild populations in a way that’s less invasive and more cost-effective than other methods.”
Observational studies of imperial eagles suggest these birds, like most large birds of prey, are at least socially monogamous. This means a male-female pair stays together throughout the breeding season and shares responsibility in raising young, DeWoody said.

But just because two individuals act like a pair doesn’t guarantee they’re not having trysts on the sly. In fact, studies over the last decade have shown most broods of socially monogamous birds include offspring from at least two genetic fathers. “Our study actually stands out as a relatively rare instance in which DNA fingerprinting uncovers genetic monogamy in a bird population,” DeWoody said. Unlike their smaller songbird cousins, most raptors are believed to be truly monogamous, and this study provides the first genetic confirmation of monogamy in at least one species, DeWoody said. “It’s very likely that other raptor biologists will follow this with similar studies on other species of interest like bald eagles,” he said.

Source: Purdue University

Bio.com
July 19, 2005

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Hummingbirds’ aerodynamics are midway between insects and other birds

An analysis shows air vortices at the tip of a hummingbird’s wings as it flies. “What led us to this study was the long-held view that hummingbirds fly like big insects,” says Douglas Warrick, of Oregon State University in Corvallis. Many experts had argued that hummingbirds’ skill at hovering, of which insects are the undisputed masters, means that the two groups may stay aloft in the same way: by generating lift from a wing’s upstroke as well as the down. This turns out to be only partially true.
Other birds get all of their lift from the downstroke, and insects manage to get equal lift from both up and down beats, but the hummingbird lies somewhere in between. It gets about 75% of its lift from the downstroke, and 25% from the upwards beat.

Warrick and his team investigated the birds’ performance by looking at the swirls of air left in their wake. To do this, they trained rufous hummingbirds (Selasphorus rufus) to hover in place while feeding from a syringe filled with sugar solution. Their wings are a marvellous result of the considerable demands imposed by sustained hovering flight.
They filled the air with a mist of microscopic olive-oil droplets, and shone a sheet of laser light in various orientations through the air around the birds to catch two-dimensional images of air currents. A couple of quick photographs taken a quarter-second apart caught the oil droplets in the act of swirling around a wing. Although hummingbirds do flap their wings up and down in relation to their body, they tend to hold their bodies upright so that their wings flap sideways in the air. To gain lift with each stroke the birds partially invert their wings, so that the aerofoil points in the right direction. Their flight looks a little like the arm and hand movements used by a swimmer when treading water, albeit it at a much faster pace.

Insects attain the same lift with both strokes because their wings actually turn inside out. A hummingbird, with wings of bone and feathers, isn’t quite so flexible. But the birds are still very efficient. “Their wings are a marvellous result of the considerable demands imposed by sustained hovering flight,” Warrick says. “Provided with enough food, they can hover indefinitely.” The researchers add that the hummingbird’s flapping bears a striking resemblance to that of large insects such as hawkmoths, an example of how evolution can produce similar engineering solutions in hugely distant animal groups.

Nature
July 5, 2005

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Wild geese flu in China

China has reported only one outbreak since March 2004 – in July, in Anhui province. The authorities blamed this occurrence on wild waterfowl on a nearby lake.

But Albert Osterhaus, a leading flu expert at the University of Rotterdam in the Netherlands, told New Scientist that it is rare to find such highly pathogenic strains of bird flu in wild fowl. As for the geese in Qinghai, he says, “we can’t be sure until we see the genetic sequence, but it is not unlikely that these cases are spillback from local poultry”. The geese could have become infected by swimming in ponds used by infected local birds. In 2003, says Osterhaus, when Dutch poultry was hit by another highly pathogenic bird flu called H7, swans using the same pond as infected farm birds caught the H7 virus.
The geese could have carried the flu with them from India only if it did not make them ill at all. “We don’t know what H5N1 does in these geese,” says Osterhaus.

Richard Thomas of Bird Life International, a conservation organisation, says the stress of their migration, during which they reach altitudes over 10,000 metres, could in theory have caused the geese to fall ill on arrival with a virus that would previously not have affected them. But no reports of H5N1 have been confirmed in India, says Osterhaus. The exhausted birds would also have been easy prey for a flu virus they met in China, he adds.

New Scientist
June 7, 2005

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How birds keep secrets in color

Songbirds are able to communicate with potential mates using plumage colors while remaining inconspicuous to avian predators, Swedish researchers suggest in PNAS this week. They do so by using colors that the larger birds are less able to discriminate from the background. Ultraviolet plumage coloration, which reflects light in the range of 355–380 nanometers, has long been known to serve as a secret communication channel in songbirds, exploiting a shortfall in the mammalian visual system. But it has not been clear how avian predators, which can see ultraviolet, are excluded. Ornithologists Olle Håstad, Jonas Victorsson, and Anders Ödeen, all based at Uppsala University, present evidence that small passerines such as the robin Erithacus rubecula, brambling Fringilla montifringilla, and golden oriole Oriolus oriolus exploit differences in the maximum sensitivities of their own visual systems and those of their potential bird predators.

Using retinal models for the songbird and predator visual systems, the researchers compared the reflectance of the head and chest plumage of 18 species of songbirds to that of their typical Swedish forest habitat. Against the appropriate background, the plumage was significantly more visible to the songbirds than predator birds, they report. “I’m really pleased to see this work published, because I always thought that the notion of UV signals being a private channel [of communication] never squared with the fact that avian predators of birds can see UV,” Innes Cuthill, professor of behavioral ecology at the University of Bristol, UK, told The Scientist. “This paper shows that, yes, there is potential mileage in the argument, because raptors aren’t as good at discriminating colors in the UV waveband as passerines,” he explained.

Evolutionary biologist David Harper, based at the University of Sussex, UK, agreed that the study “introduces an interesting idea that songbirds can communicate with each other without being conspicuous.” However, he also expressed concern over some aspects of the paper, particularly the lack of detail regarding the methodology and some of its assumptions. “This is one of those cases where we have to curse word limits,” he said. “Hopefully, future papers in less prestigious journals will be more enlightening.” Peter McGregor, a behavioral ecologist at Cornwall College Newquay, whose own research has centered on animal signalling, noted the “striking comparison with bioacoustics,” in particular the private “seeet call” (reference 1) of some bird species. But he also echoed Harper’s concerns. While studying sound is relatively straightforward, he told The Scientist, understanding color and the visual sense is much more challenging. For example, plumage signals are “omnidirectional and always on”, in addition to being subject to large variations in light regime throughout the course of the day, season, or year.

McGregor pointed to the study’s reliance on retinal models of both songbird and predator visual systems. Just looking at retinal pigments isn’t enough. “Retinas are hooked up to brains, and brains can do all sorts of flashy processing,” he said. In addition, there is a crucial distinction to make between what is signal and what is information; only the former is the result of selection. “Håstad et al. have found a correlation, not direct evidence of a private communication channel.” Ödeen admitted this is only the start, but emphasizes the nature of the differences between songbird and raptor/corvid visual systems. “We are looking at the tuning of maximum sensitivities. Raptors are sensitive some way into the UV [range], but their maximum sensitivity lies elsewhere,” he told The Scientist. “As the title of the paper suggests, songbirds are less conspicuous, not inconspicuous.”

Reference 1:http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=726695&dopt=Abstract&holding=f1000

E-mail address The Scientist Daily
May 24, 2005

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Rare condor chick hatches at Oregon zoo

A rare California condor chick pecked its way out of its egg at the Oregon Zoo’s captive breeding compound Monday, bringing the known number of the endangered species to 245. The chick’s foster mother wrapped the downy newborn in her soft breast feathers and delivered the first feeding of regurgitated raw meat.

It is the first chick this season for the zoo, which opened the nation’s fourth California condor captive breeding program in 2003. Two more eggs from different females are due to hatch in early May. Monday’s chick is about 4 inches long and an estimated 8 ounces to 9 ounces. Its sex is unknown.
The egg was laid Feb. 21 and moved to an incubator two weeks later. During a routine check Friday, keeper Shawn St. Michael saw evidence that the chick was ready to bust out because of the pattern of cracks in the shell. He moved it to a nest where another pair had been incubating a phony egg. Monday afternoon, Joe Burnett, assistant curator for condors, tossed fresh food into the enclosure, luring the female from the nest. He watched the chick pop the top off its shell “like a little lid,” Burnett said.

In the early 1980s the known California condor population had dropped to 22. The Oregon Zoo’s program is part of an effort to revive the species. In a recent contest, the zoo decided on a name for the chick: Tatoosh. In Yurok tribal legend, Tatoosh was the thunderbird that shook the mountains with its flapping wings. The two chicks produced in Oregon last year are in California. The male is to be set free this year at Pinnacles National Monument, south of San Jose. The female, who was to be released in Baja, Mexico, is recovering from tail injuries at the Los Angeles Zoo.

Yahoo
May 10, 2005

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Probable psittacosis outbreak linked to wild birds

In autumn 2002, an outbreak of probable psittacosis occurred among residents of the Blue Mountains district, Australia. We conducted a case-control study to determine independent risk factors for psittacosis by comparing exposures between hospitalized patients and other residents selected randomly from the telephone directory. Of the 59 case-patients with laboratory results supportive of psittacosis, 48 participated in a case-control study with 310 controls. Independent risk factors were residence in the upper Blue Mountains (odds ratio [OR] 15.2, 95% confidence interval [CI] 5.6–41.7), age of 50–64 years (OR 3.9, 95% CI 1.5–10.5), direct contact with wild birds (OR 7.4, 95% CI 2.5–22), and mowing lawns without a grass catcher (OR 3.2, 95% CI 1.3–8.0). Protective equipment is recommended for residents in areas frequented by free-ranging birds if contact with birds and their droppings is likely when performing outdoor activities such as lawn mowing.

Psittacosis is a human disease caused by infection with the bacterium Chlamydophila psittaci. The bacterium also causes avian chlamydiosis, a disease reported in psittacine birds such as parrots, cockatiels, and parakeets. Chlamydophila psittaci can be present in large numbers in the droppings of sick birds and in dust contaminated by infected droppings. The organism can remain infectious in the environment for months. Human infection usually occurs when a person inhales the bacterium shed in feces and secretions of infected birds. Sheep, goats, cattle, and reptiles can also be infected, but these animals have rarely been linked to human cases.

Psittacosis has an incubation period of 1 to 4 weeks, and manifestations of disease can range from asymptomatic infection to systemic illness with severe pneumonia. Untreated psittacosis has a reported case-fatality rate of 15% to 20%. Psittacosis is most commonly reported among people in close contact with domestic birds, such as bird owners, poultry farmers, veterinarians, and workers within pet shops and poultry-processing plants. Sporadic cases and an outbreak in Australia linked to contact with free-ranging (wild) birds have been reported; however, little information is available on the role of wild birds in the transmission of Chlamydophila psittaci to humans.

Psittacosis became a notifiable disease in New South Wales (NSW), Australia, in 2001, and 38 laboratory notifications were received by the state health department that year, an incidence of 5.7 cases per 1,000,000 population for NSW. In May 2002, clinicians at the Blue Mountains Hospital (BMH), in the Wentworth Area Health Service, NSW, a 1-hour drive west of Sydney’s central business district, reported an increase in adult admissions for severe community-acquired pneumonia. From March to May 2002, a total of 160 persons with pneumonia were seen at the BMH emergency department, compared with 82 from March to May 2001. The population of the Blue Mountains is ˜80,000 persons, and the area includes a large national park. The lower Blue Mountains (altitude ˜160 m) is on the western outskirts of Sydney, and residences tend to have suburban-style yards. The upper Blue Mountains district (altitude ˜1,044 m) lies further west, receives more rain, and has more bush land; its residential areas have larger yards and are closer to bush land. Reports that patients had found increased numbers of dead free-ranging birds in their yards, handled dead birds, and occasionally mowed over dead bird carcasses prompted clinicians to suspect psittacosis, although no case had been confirmed by laboratory testing. We report on our investigation into the extent and most likely cause of this outbreak.

Emerging Infectious Diseases
March 29, 2005

Original web page at Emerging Infectious Diseases

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New York high-rise hawks have egg in nest

Pale Male and his mate, Lola, who live on the ledge of a Fifth Avenue apartment building overlooking Central Park, have at least one egg in their nest, according to the Pale Male.com Web site run by Lincoln Karim, a video engineer with Associated Press Television News who devotes most of his spare time to monitoring the birds.

In December, the board of the co-op apartment building, whose tenants include actress Mary Tyler Moore and CNN anchor Paula Zahn, removed the hawks’ huge nest on a 12th-story ledge, calling it a hazard. The board later bowed to public outrage and pressure from the city and environmentalists, and restored a row of anti-pigeon spikes that the hawks had used to anchor their nest. Pale Male and Lola immediately rebuilt their nest.

The male hawk has sired 23 chicks with four mates since he first set up housekeeping at 927 Fifth Ave. in 1993. “Lola appears to be turning the eggs every half hour or so. Pale Male had two sittings today between noon and sunset,” said an entry posted Sunday.

Yahoo
March 29, 2005

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‘Symptomless’ bird flu cases raise concerns

The H5N1 bird flu virus might be acquiring a greater ability to spread from human to human, recent cases in Vietnam suggest. But as two elderly relatives of patients killed by the bird flu test positive for the virus and yet have no symptoms, there are also indications that it may not be as lethal as currently thought.

The 2004 outbreak of H5N1 in Vietnam stopped in spring after the country killed millions of infected and exposed poultry. But outbreaks resumed in December, probably because the virus persisted in ducks showing no symptoms, say flu experts. Since December, 22 people have tested positive for H5N1 in Vietnam, of whom 14 have died, including one woman from Cambodia. Five of the cases occurred in clusters that suggest the virus passed from person to person. In the most recent, a 14-year-old girl fell ill on 14 February, her 21-year-old brother on 21 February, and a 26-year-old male nurse who cared for the brother, on 26 February.

Spread of the virus to health care workers would be worrying, says leading flu expert Robert Webster at the St. Jude Children’s Research Hospital in Memphis, US. Attending a conference on microbial threats in Lyon, France, last week, he told New Scientist: “That’s where we’d expect to see the first cluster if this virus starts spreading among humans.” This is what happened in 2003 with the previously unknown respiratory virus SARS – Sudden Acute Respiratory Syndrome. The Vietnamese cases might have acquired the virus from poultry, especially from raw duck products eaten during the recent Tet New Year’s festival. But because they each developed symptoms several days apart, investigators from the World Health Organization suspect human to human transmission.

The investigation has uncovered other surprises. The WHO found antibodies to H5N1 in the 81-year-old grandfather of the brother and sister, meaning he has been infected but survived. And the healthy wife of a 69-year-old man who died from H5N1 on 24 February has also been found to have the antibodies. It is unclear if the people with antibodies were infected with H5N1 at the same time as their relatives, but did not get sick. This would suggest that many infections have been going undetected, as the healthy contacts of people who get H5N1 have not been widely tested. That in turn would mean that the virus might not be as lethal as it appears from the confirmed cases, of whom nearly three-quarters have died. But it also means that many more people than suspected have harboured H5N1, and each of them is an opportunity for the virus to adapt further to humans.

H5N1 flu is thought to have been circulating in Vietnamese poultry for several years, however. The people with antibodies might have fallen ill and recovered some time ago, before anyone tested for H5N1. Or low-level exposure to the virus in poultry might have immunised them without significant illness.

New Scientist
March 29, 2005

Original web page at New Scientist