This year on Bird Island everything seems to be late! We visited for ten days in mid-June, having heard that Sooty Terns had not begun laying when I first arrived in Seychelles at the end of May. During our stay on the island laying was in full swing, but we also found that many Sooty Terns were still arriving and laying their eggs.
The island’s largest birds were also conspicuous by their virtual absence. The tall Casuarina trees within and adjacent to the Sooty Tern nesting area have normally provided a roosting site for hundreds of frigatebirds and, in recent years, Red-footed Boobies. Roosting birds have normally been present throughout the day, but numbers are much higher in the evenings and overnight. This year, however, the Casuarinas had empty branches. The evening arrival of Red-footed Boobies from the northwest did not materialise, and few frigatebirds soared over the island in the evenings. The lack of these magnificent birds was doubtless a relief for returning Sooty Terns, and also Brown and Lesser Noddies, which in previous years have been harassed by frigatebirds in order to make the terns and noddies regurgitate their recent meals, providing the frigates with easy dinners.
Besides the Sooty Terns, the island’s other most common terns, the two noddy species, were also behind their normal schedule this year. Lesser Noddies were busy collecting nesting material (dead leaves normally collected from the ground) and building their nests in trees, whereas in most recent years by mid-June many have laid their single eggs, and a few even have chicks. And by the time we left Bird Island on 23 June, we had not seen a single egg in the nests of Brown Noddies, most of which were still gathering nesting material and indulging in courtship behaviours.
The late laying of Sooty Terns and Brown Noddies, and the lack of Frigatebirds and Red-footed Boobies, suggest that something is amiss at sea.
Since our last visit to Bird Island in 2022, the island’s coasts have undergone dramatic changes. The east coast has suffered extensive erosion, such that an area of bush and open ground on the north-east coast, formerly occupied by large numbers of nesting Sooty Terns was washed away. Further south on that coast the beach has vanished, exposing beach sandstone rocks that I have not seen since the early 1970s, although Christine saw them to a much lesser extent in the 1980s. Other than those times, that area has been an extensive sandy beach for the last 40 years.
The sand promontory at the north of the island is huge this year. In 2022 it was less extensive and just before we left the entire sand bank was awash with sea surges during high spring tides, washing away most of the Sooty Tern nests, eggs and chicks that had been established on the sand bank close to the main colony area. Even the island’s west coast is showing signs of erosion, especially towards the north along the seaward edge of the Sooty Tern colony. However, the main part of the colony away from the beaches is in good shape, occupied by huge numbers of nesting birds.
After three years of La Niña climate conditions, a new and severe El Niño event is predicted to be brewing in the central Pacific Ocean, bringing more extremes of weather globally. Whether the erosion of Bird Island’s beaches over the last year is associated with this climate anomaly is probably too early to say. However, the erosion illustrates the vulnerability of low-lying islands, and to their wildlife and human activities, to ocean warming, sea-level rise and potential storm damage.
Despite the lateness of this year’s breeding season, Bird Island’s Sooty Terns had arrived in good and typically spectacular numbers, with high densities of nests in the main part of the breeding colony. In addition, birds had begun nesting among flotsam, mainly the dead remains of beach-crest vegetation killed by earlier high tides and erosion. And the northern beach, where seedlings of typical beach crest plant species had germinated, had also attracted large numbers of nesting birds. The future of these nests, and their eggs and chicks, is uncertain however, as they could be vulnerable to sea surges over the northern sand bank during high tides as the south-east trade winds intensify towards their peak in July-August.
Wild Bird Conservation 