Avian Flu Mutation Threatens Thousands of Seabirds in Scotland – National Geographic UK

“What we’ve seen with this particular strain of virus is that it seems much easier to transmit,” says Ruth Cromie, Adviser for Wildlife Health at the Convention on the Conservation of Migratory Species of Wild Animals. It is not yet clear how this new form of the virus has been transmitted from winter to spring, but it puts seabird populations at especially high risk as they congregate in dense breeding colonies. Scotland is home to around half the world’s breeding population of gannets, the largest seabird in the North Atlantic and close relatives of tropical boobies. The Shetlands have traditionally been a stronghold for them, in part because being close to the edge of the European continental shelf, the surrounding seas, which surge, are very productive and full of food. In mid-July, visitors traveling by boat from the Shetland capital of Lerwick to the nearby island of Noss are met by the sight of thousands of gannets nesting on the narrow ledges of the sheer sandstone cliffs of 182 meters. The air is filled with birds, soaring like arrows from all directions, making their way to the din of the shrill calls of the kraak kraak. From time to time, the wind emits gusts of fish guano, coming from the solid spots that hang like stalactites from the ledges. However, a closer look at the gannets through binoculars reveals dead bodies slumped between the nests. At the base of the cliffs, the water currents have dragged a raft of white lumps formed by the recently fallen corpses. A short distance away, a large skua – a species of bird – feasts on one of the floating gannets. During this spring and summer, the devastation was even harder to ignore at times. Phil Harris, a tour guide who takes visitors to the Noss seabird colonies, describes how his boat navigates the floating bodies of 50 or 60 gannets. “On three occasions we had dead adult birds come from somewhere on the cliff and drop dead alongside the boat,” he says. (Related: How Many Birds Are There in the World?) Infecting the Food Chain In addition, other worrying changes in bird behavior are taking place. Scotland is home to around 70 percent of the world’s breeding population of large skuas, notoriously aggressive birds that swoop down on anyone who dares to approach their nests and harass other birds for free food. On Noss, Harris regularly sees flocks of great skuas chasing gannets, forcing them to regurgitate their catch. “You don’t see that now, probably because there are so many dead gannets to feed on,” he says. In some cases, within hours, birds begin to show neurological signs of infection, becoming disoriented as the virus replicates in their brains and causes multi-organ failure. Gannets have been observed sitting helplessly on beaches in Shetland, apparently unable to see. After the great skuas scramble their carcasses, their infection is evident, as some circle themselves in the air. “It’s heartbreaking to watch when they’re normally so full of attitude,” says Kevin Kelly. “These are huge birds that can’t hold their own heads up. It affects them tremendously neurologically.” At the population level, the situation is even more worrying. Skua numbers on Shetland have been reduced by at least half compared to last year. In some places, only one in ten birds survives. James Pearce-Higgins has received similar reports of mass skua mortality on other Scottish islands. If the current trajectory continues, the species could be a year or two away from extinction. So far, reports of gannets are not that serious, but in some colonies up to a quarter of the adults have already died this breeding season. Elsewhere, entire colonies of young are being wiped out, including terns on the island of Texel in the Netherlands. Hundreds of roseate terns have died on Coquet Island, the UK’s most unique seabird colony. “You can quickly see how this can translate into a really big global impact for these species,” says Pearce-Higgins. Added stressors Many of the seabirds that are contracting the virus are long-lived and reproduce slowly. Skuas take about seven years to reach maturity and lay two eggs a year. Gannets only lay one. This means that any recovery of populations will be innately slow. “This is an impact that will be seen for decades,” says Pearce-Higgins. Pearce-Higgins compares this outbreak of avian flu in seabirds to the devastating decline in populations of bald eagles, peregrine falcons, and many other birds of prey due to DDT poisoning, which American author Rachel Carson brought to the public’s attention. in his 1962 book Silent Spring. The ubiquitous pesticide contaminated food webs, thinned the shells of birds and killed their embryos. “The priority is to understand what’s left,” says Pearce-Higgins. Seabird populations now being reduced by bird flu are already at risk from many other threats. More than half of seabird species are thought to be in decline, with the combined threat of climate change, overfishing of their prey, bycatch in fisheries, and non-native predatory mammals eating their eggs and chicks. like rats and cats. In addition to being sentinels for the health of the oceans, seabirds also play vital roles in marine and terrestrial ecosystems. They carry essential nutrients in their faeces, and as top predators in the ocean, many species of seabirds help regulate the rest of the food web. Just as the ocean misses sharks when they are overfished, the decline of seabirds could also have major repercussions and likely upset the balance of ecosystems, including those that support major fisheries. “We have been talking for a long time, as have many conservationists, about the decline of seabirds and the pressures they face,” says Kevin Kelly of the RSPB. “This is something new that was not on the radar.” A response strategy The big question, unanswered at the moment, is what is going to happen. So far, there is only one asymptotic report of this avian flu strain jumping to humans, although future zoonotic outbreaks remain a possibility. As for wildlife, a worrying prospect is that migratory seabirds will transfer this transmissible new form of the virus to more populations, particularly in the southern hemisphere, which has so far been largely unaffected. It is not yet clear which species can carry the virus asymptomatically. James Pearce-Higgins believes that one group of birds in the UK that could be acting as a vector for the virus is seagulls. “They occupy a lot of the wetland areas where some of these waterfowl will have been and then potentially go to seabird colonies to breed,” he says. The last time a winter census of gull populations was carried out in the UK was in 2006, and Pearce-Higgins hopes this emergency will help raise funds to repeat the surveys this year. In the meantime, what he urges, according to Ruth Cromie, is to put national and regional response plans in place before more outbreaks occur in wild birds. Possible strategies she suggests include not building poultry farms near wild bird colonies, keeping dog walkers out of important areas, and creating no-fly zones to prevent bird stress while nesting. Authorities also need to know if it’s a good idea to pick up bird carcasses, a question that has remained unclear throughout the current outbreak. “These are not the last crises that are going to happen on our increasingly polluted planet with all these different interfaces between wildlife and people,” he says. Until now, most attention has focused on monitoring the virus among domestic birds. Many conservationists and scientists advocate much greater funding to study the spread of the virus among wild birds. Kelly hopes the avian flu crisis will help convince governments to put more money into conservation programs that help reduce obvious and pre-existing threats to seabirds so they have the best possible chance of recovering. On Shetland, locals nervously wait for the breeding season to end and for the seabirds to abandon their nesting sites and disperse, hoping this will bring temporary relief this year. “I want this season to be over and the birds gone, to try and get this over with,” says Shetland Seabird Tours Manager Phil Harris. “Then we’ll see what comes next year.”