BirdLife: The Magazine Jan-Mar 2018 - Page 21

attract seabirds; caught petrels, fulmars and shearwaters to sample their diets and take biometric measurements – and then, of course, released them; and spent hours up on deck on watch in the hopes of spotting whale blow and deciphering shadowy shapes below the surface. as a treasure trove of marine biodiversity in the high seas following analysis by a collaboration of over 60 seabird scientists. Rigorous seabird data-tracking analysis revealed the site to be an important seabird hotspot in the North East Atlantic with a very high number of individual birds – potentially as many as five million throughout different seasons, with the highest use in winter. The site also supports a high number of different bird species. It is an Important Bird & Biodiversity Area (IBA) for 23 species, including Atlantic Puffin Fratercula arctica (Vulnerable), Black-legged Kittiwake Rissa tridactyla (now also assessed as Vulnerable), Bermuda Petrel Pterodroma cahow, and Northern Fulmar Fulmarus glacialis, as well as long-distance migrants such as the indefatigable Arctic Tern Sterna paradisaea. Even species from the other end of the Atlantic, such as South Polar Skua Catharacta maccormicki and So oty Shearwater Ardenna grisea, join the feast. Seabirds are an intrinsic part of marine food chains. More easily monitored than their underwater counterparts, seabirds can act as a ‘homing beacon’ to identify marine biodiversity hotspots. The crew embarked on their voyage hoping to witness high numbers of seabirds, and find out about the hotspot’s use by other marine animals including cetaceans, turtles and sharks. During Discovery’s month-long journey, the seabird and cetacean teams brewed up huge vats of fish ‘chum’ (a foul-smelling concoction of fish bone, guts and oil) used to Jan-Mar 2018 • birdlife Marguerite Tarzia releasing a Leach’s Storm-petrel Hydrobates leucorhous Photo Julie Miller 0 7 Great Shearwater Ardenna gravis Photo Simon Pinder the site was identified by birdlife as a treasure trove of marine diversity in the high seas Claire Lacey, a marine-biologist with over 35,000 nautical miles of marine mammal survey experience, explained, in a blog post written during the journey, how the cetacean team were using both visual and acoustic survey methods to assess the distribution of whales and dolphins. An underwater ‘recording studio’ called a hydrophone array, capable of withstanding tough weather conditions, was towed 200 m astern of the ship, continuously recording sounds beneath the waves. This allowed the team to detect and localise certain species of marine mammals, such as the deep-diving Sperm whale, while in deep fog or low light. The seabird catching team, as PhD researcher Julie Miller explains, was quite the spectacle to behold, with various nets and poles as they trialled innovative techniques to safely catch seabirds in tough conditions. A cast net was ultimately found to be the most effective for catching birds, although carrying this off successfully when poised at the end of the ship, three metres off the water, was no mean feat. After a month out in the expansive – sometimes inhospitable – ocean, land finally came into sight as the ship crossed the fabled Grand Banks of Newfoundland, on its way to St Johns, Canada. The Discovery’s wild, Atlantic journey had been accompanied by a dazzlingly rich panoply of marine life: shearwaters, fulmars, storm-petrels and more; common short-beaked, striped, bottlenose and Atlantic white-sided dolphins; pilot, humpback, minke, sperm, fin, sei and – incredibly – blue whales. Yet, as Tarzia laments: “There have also been the tell-tale signs of humans, and the impact we are having on the planet.” In several cases, sampling revealed “bird stomachs full of plastic”, and the oceanographic work found water from the cold 21