#sternidae

First evidence of the impact of climate change on Arctic Terns

Data collected from electronic tags retrieved from 47 journeys made by the Farne Island Arctic Terns, has revealed for the first time how climate change might affect their behaviour.

Arctic Terns spend their breeding and non-breeding seasons in polar environments at opposite ends of the world and are our longest-migrating seabird.

Spending their non-breeding season in the Antarctic, the remoteness of this part of the world means that until now we have had a very limited understanding of their behaviour and distribution while they are there.

Analysing the data from 47 migrations over two study years, 2015 and 2017, the team found:

• Arctic Terns live on the Antarctic ice for one third of their annual lifecycle.

• Analysis of their feathers shows their main food source is krill or similar crustaceans.

• There were marked differences in the bird's behaviour and distribution between those tagged in 2015 compared with those tagged in 2017. This coincided with a substantial change in ice conditions, with high ice cover in 2015 followed by unusually warm conditions which led to the break-up of the ice in late 2016 and lower ice cover than normal throughout the following year.

Dr. Chris Redfern, of Newcastle University, UK, who has led the study explained:

"Sea ice is an important habitat for juvenile krill as it provides protection from predators and from the intense light of the Antarctic summer.

"We now know that krill are the main food source for the Terns so it seems likely the warmer weather during 2016/2017 led to reduced krill abundance and so the birds were forced to forage in different areas.

"And in fact, in that second year, the birds converged on the Shackleton Ice Shelf rather than being spread out along the East Antarctica coastline.

"Polar regions are particularly sensitive to climate change and even small shifts can have major implications throughout the entire food web.

Royal Tern Thalasseus maximus

Asia’s rarest seabird could be easier to spot in the future | BirdLife

You see it’s tough being naturally sociable when there’s no-one left to hang around with. The Chinese Crested Tern is a very gregarious species, relying on the presence of a large colony to feel comfortable enough to breed successfully. Late-breeders will even desert their nests if the colony starts to disperse, according to close observation by BirdLife’s Simba Chan, Senior Conservation Officer of BirdLife Asia Division and National Geographic Explorer, when he dedicated two breeding seasons in 2014 and 2015 carefully camped out (relying on shipment of food and water, and braving a typhoon) on the Jiushan Islands (off the coast of Zhejiang, southeast China [see map below]) in order to protect newly-found Chinese Crested Terns there (amongst Greater Crested) from disturbance. The 2016 discovery in South Korea also indicates that Chinese Crested Terns there are breeding earlier than normal in order to match the breeding times of the Black-tailed Gulls.

The key, therefore, to the conservation of Chinese Crested Terns is increasing nesting success by making the birds feel safe. This is achieved through preventing disturbance and by using social attraction techniques, such as using model decoy birds and call-playback systems to bolster the colony. Almost three years later, this kind of direct conservation effort is paying off in South Korea: this breeding season seven Chinese Crested Terns were monitored at the South Korean island, with at least one chick fledged.

Social attraction techniques were developed by Dr. Stephen Kress (Vice President for Bird Conservation, National Audubon Society [BirdLife USA]) for the restoration of Puffin colonies in the USA in 1970s, and has proven to be effective in restoring colonial seabird breeding sites. Since 2013, the adaptation of these techniques by Chan and colleagues has successfully restored the deserted Chinese Crested Tern breeding colony of the Jiushan Islands, leading to a record-breaking number of Chinese Crested Terns being found there (over 50!) during Chan’s protective stake-out seasons, doubling the known population at the time. This shows that the islands along the eastern China coast were highly disturbed (and perhaps even exploited) and so the terns congregated on the one island that had been made safe. Chan then recommended the use of social attraction to help the South Korean birds.

“I am pleased that social attraction methods have helped Chinese Crested Terns establish new colonies” said Dr. Kress. “This is good news for the species. Multiple nesting colonies within an expanded range reduces the risk of having most of the population in one location. Because each site brings its own risk to the species, multiple sites help to assure that some of the population will survive regardless of what happens at other colonies.”

Black Tern flying (via U.S. Fish and Wildlife Service Northeast Region)

Black tern photographed at Missisquoi National Wildlife Refuge

White Tern (Manu o Ku, Gygis alba) (via USFWS - Pacific Region)

Photo Credit: Brian Peck/USFWS

Rose Atoll is located approximately 130 nautical miles east-southeast of Pago Pago Harbor, American Samoa, and is the easternmost Samoan island and the only atoll in the Samoan Archipelago. It is the southernmost unit of the National Wildlife Refuge System and shares the distinction with Jarvis Island of being the only National Wildlife Refuges located south of the equator.

Rose Atoll is nearly square, with the ocean-side slopes about 1 mile in length. It is one of the smallest atolls in the world, consisting of two low sandy islets, Rose and Sand. Each is located on a coralline algal reef rim enclosing a lagoon. A single, natural pass with a minimum depth of 8 to 48 feet deep links the lagoon to the sea. The lagoon is a maximum of 1.2 miles wide and up to about 65 feet deep, and includes 1,575 acres. Rose and Sand Islands cover areas of about 14 and 7 acres respectively.

Migratory seabird deaths linked to hurricanes

Stronger and more frequent hurricanes may pose a new threat to the sooty tern, an iconic species of migratory seabird found throughout the Caribbean and Mid-Atlantic, a new Duke University-led study reveals. The study, published this week in the peer-reviewed open-access journal PeerJ, is the first to map the birds' annual migratory path and demonstrate how its timing and trajectory place them in the direct path of hurricanes moving into the Caribbean after forming over the Atlantic.

"The route the birds take and that most Atlantic-forming hurricanes take is basically the same, only in reverse," said Ryan Huang, a doctoral student at Duke's Nicholas School of the Environment, who led the study. "That means these birds, who are usually very tired from traveling long distances over water without rest, are flying head-on into some of the strongest winds on the planet."

"This is worrying because we know that as Earth's climate changes, we expect to see more frequent and powerful hurricanes in the future—meaning that the chances of sooty terns being hit by storms will likely go up," Huang said.

Hurricane season typically lasts from June to November, with peak activity occurring in August and September. A new map produced by the research shows that sooty terns leave their breeding colony at Dry Tortugas National Park in the Florida Keys each June as hurricane season starts. They migrate southward and eastward across the Caribbean through summer and early fall, before skirting the northern coast of South America and arriving at their winter habitat off the Atlantic coast of Brazil in November.

Huang and his colleagues charted the migratory path by recording and mapping the dates and locations of all sooty terns banded for study at the Dry Tortugas since the 1950s but found dead elsewhere. They also mapped locational data retrieved from birds that were fitted with satellite-telemetry tracking tags. When they overlaid all this data with maps of hurricane paths from the same period, they discovered a striking correlation.

"While it's impossible to say just how many of the birds died as a direct result of the hurricanes, we saw a strong relationship between the numbers and locations of bird deaths and the numbers and locations of hurricanes," said Stuart L. Pimm, the Doris Duke Professor of Conservation Ecology at Duke's Nicholas School. "What's really interesting is that it's not just the big category 4 and 5 storms that can kill large numbers of birds. A series of smaller, weaker storms may have the same impact as that of a single large, strong storm," Pimm noted. "In September 1973, Tropical Storm Delia, a small storm in the Gulf of Mexico, killed a lot of birds because they were in the wrong place at the wrong time."

Although sooty terns are neither rare nor endangered—80,000 or more of them are estimated to breed in the Dry Tortugas each year—they have long been used by scientists as an indicator species to determine the health of the region's marine environment.