In the United Kingdom, the North Sea saw an apian breeding collapse in the year 2004. The direct cause for this crash was a shortage of sandeels, a small fish essential to the diet of many birds, including the Hercules of all apian migrators: the Arctic Tern. This shortage of food was related to global warming, and according to the World Wildlife Fund Global Climate Change Program, “Warming ocean waters and major shifts in species that underpin the ocean food web are thought to be behind the major sandeel decline.”
The Arctic Terns (see figure 2) demonstrate perfectly how susceptible migratory birds are to climate disruptions, especially since this is a bird whose annual journey round-trip totals between 22,000 and 30,000 miles. Since Arctic terns live up to 30 years, a single one of these 14-17 inches long, two-pound birds may travel during its lifetime more than 650,000 miles. Interestingly enough, Arctic terns see more daylight than any other creature on the planet, “since they are in both the Arctic and Antarctic during the periods of longest days.”
Arctic Terns rely on the North Sea (see the map on figure 7) as a source of food in their long journeys. In the year 2004, the terns saw their habitual feeding stop unable to supply them with enough food. In fact, “no Arctic tern chicks were reared in the south of Shetland [archipelago in Northern Scotland] in 2004. And although hundreds of Arctic Terns arrived at the RSPB’s [a wildlife reserve owned by BirdLife International, UK] Mousa reserve this spring, no young were fledged. All the large Arctic Tern colonies in Orkney [Northern Scotland] failed, and for the first time in living memory, none nested at the RSPB reserve on Papa Westray [also in Scotland].” The Terns were not alone in their plight: “The nearly 7,000 pairs of Great Skuas in the Shetlands [another species dependent on the North Sea for food] produced only a handful of chicks and starving adult birds ate their own young.”
Figure5: An Arctic Tern, and its migration route, from the National Wildlife Federation website.
The collapse of fish productivity in the North Sea in the year 2004 has been called by scientists “a regime shift” because “rising sea temperatures have fundamentally changed the plankton mix to the detriment of sandeels,” the fishes that are essential as part of the diet of the many birds that stop in the North Sea to feed, as reported by BirdLife International in a press release entitled “Seabirds in the North Sea: victims of climate change?” Sandeels also are essential to other links of the marine food chain, which means that other fish and bird species have started to see their numbers drop as well, such as mackerels, cod, or kittiwakes (a seabird). The 2004 collapse “was so severe that fishermen voluntarily shut down the fishery in the worst affected area” of the United Kingdom’s North Sea. The Marine Policy Head of BirdLife International concluded that “We could be witnessing the single biggest change in the North Sea since it was formed 10,000 years ago.”
