Do migrating birds spread Bird Flu?

It’s the bird migratory season again. With the start of the season, another threat comes. The Bird Flu.

In 2005 an outbreak of the H5N1 'bird flu' virus in South East Asia led to widespread fear with predictions that the intercontinental migration of wild birds could lead to global pandemic. Such fears were never realised, and now research published in the Journal of Applied Ecology reveals why the global spread of bird flu by direct migration of wildfowl is unlikely.

The highly pathogenic H5N1 virus is primarily a disease of poultry, often resulting in mass mortality. However, the virus can also infect other species, including wild birds and humans. Some wild ducks, geese and swans can carry the virus asymptomatically, (without showing any symptoms) meaning that they have the potential to spread the virus as they migrate.

"The actual risk of H5N1 spread through migratory birds depended on whether infected individuals were capable of migratory movements while shedding virus, and the distance over which such individuals could travel. Our research has answered these questions using analysis of infection and migratory routes and timings for many bird species" says Dr Nicolas Gaidet.

His team analysed 228 birds from 19 species using satellite telemetry from 2006 to 2009 over the bird flu affected areas of Asia, Europe and Africa. The results indicated that migrating wildfowl are capable of dispersing the virus over extensive distances as much as 2900km before symptoms become apparent.

However, while this is theoretically possible the team found that direct virus dispersal by migrating birds would require asymptomatic infection to coincide precisely with the migration season. The results revealed a very small 'window' of between 5 to 15 days when dispersal of the virus over 500 km could occur.

It is crucial to the spread of disease over such a distance that an infected bird must not be showing the symptoms of infection. If the symptoms are evident then it is highly likely that the individual may not migrate, or at least they will be unable to cover the distance as well as a healthy bird.

Read the research paper here

Bar-Tailed Godwit Sets Record for Long-Distance Flight

How is it possible to fly 11,000 kilometers without a single break? The record holder for long distance flight outdoes all human-made aircraft. Every year the Bar-tailed godwit undertakes an eight-day journey of 11,000 km between Alaska and New Zealand twice. The bird flies non-stop, without once breaking the journey to rest or eat.

Professor of Ecology Anders Hedenström from Lund University has pondered over how this species of bird can fly so far without stopping. The distance is twice as far as previously known non-stop distances for migratory birds.

Professor Hedenström emphasises that the bar-tailed godwit is far superior to all aircraft constructed by humans when it comes to the art of flying for a long time without a break. The best man-made flying machine with a record closer to that of Bar-tailed Godwit is QiniteQ's Zephyr, an unmanned solar-powered craft which remained in the air for 82 hours, (around 3.5 days), compared with the Bar-tailed Godwit's eight-day flight.

But what is it that makes the bar-tailed godwit able to fly 11 000 kilometres without a single break? How can these birds manage without sleep or food for eight whole days? One explanation is that they consume unusually little energy compared with other species of bird. Anders Hedenström has calculated that the bar-tailed godwit consumes 0.41 per cent of its body weight each hour during its long flight. "This figure is extremely low compared with other migratory birds," he says.

There are still pieces of the jigsaw missing that could explain the bar-tailed godwit's record non-stop flight. Could the bird's success be due to a particularly good ability to navigate with the help of an inner compass that makes use of the earth's magnetic field, for example? Anders Hedenström notes that there are a number of exciting questions surrounding the bar-tailed godwit's ability not to get lost up in the air.


Read the full story here.

Read the journal article “Extreme Endurance Migration: What Is the Limit to Non-Stop Flight?”
Photo: Lars Hedenström (www.sciencedaily.com)

Red List Indices to measure the sustainability of species use and impacts of invasive alien species

After habitat loss and degradation, the leading threats to biodiversity are over-exploitation and invasive alien species. For birds, newly synthesised data using the standard classification schemes for utilisation and threat types for the IUCN Red List allow novel analyses on the importance of these threats and permit the calculation of Red List Indices (RLIs) to show trends in the status of birds driven by these factors.

Evidence of utilisation by humans was found for a total of 4,561 bird species, representing 45.7% of the world’s 9,990 extant and extinct bird species. Among these, two purposes of use dominate:

· 3,649 species (37.0% of extant species, 87.4% of utilised species) were recorded as being used as pets, and

· 1,398 species (14.2% of extant species; 33.5% of utilised species) were recorded as being hunted for food.

Less significant uses include sport hunting, wearing apparel or ornamentation and traditional medicine , with small numbers of species being recorded as used for handicrafts, fuel (from oil or fat, principally from seabirds) and household goods (e.g. down for mattresses), etc. Many species are used in more than one way; for example, 68.9% of species that are hunted for food are also kept as pets.

Much of this use drives trade at an international scale, involving at least 3,337 species, mostly for the pet trade. RLIs show that although successful control and management of use and trade have led to some species improving in status, this has been outweighed by the number of species deteriorating in status owing to unsustainable exploitation. Overall, the RLI showing trends in extinction risk driven by issues related to use shows a negative slope: human use of birds is currently unsustainable. Similarly, and of relevance to the Convention on the International Trade in Endangered Species (CITES), the RLI for internationally traded bird species showing trends in extinction risk driven by issues related to international trade is also declining: international trade remains a threat to the world’s birds.

Invasive species impact at least one third of the world’s threatened bird species (398 species, 32.6%), with mammals being the most important (impacting 81.1%), particularly through predation by carnivores and rodents. The RLI illustrating impacts of invasive species shows that they are driving deterioration in the status of the world’s birds. RLIs for the impacts of use and invasive species will be important indicators to help track progress towards the target of significantly reducing biodiversity loss by 2010.

This article is written by Stuart H.M Butchrtfull and published by the Bird Conservation International.