The 22 July new moon generated high spring tides, which is normal. The return of strong south-east trade winds, however, generated roughening seas with heavy ocean swells. This combination led, during the evening of 24 July, to large waves crashing on to Bird Island’s western beach, sending massive surges of water over the beach crest and into nearby parts of the Sooty Tern colony. Large pools of sea water accumulated, full of swirling debris of floating driftwood and settling sand that had been washed inshore. In the part of the Sooty Tern colony affected, eggs that had not yet hatched were washed away and the pools of sea water were full of desperately struggling chicks and even some adults that had become waterlogged.
All of the chicks were very young and mostly still covered with fluffy down. This had become soaked, a situation made even worse by some chicks being coated with wet sand that hampered their struggling to reach floating wood or dry land on which they could stand clear of the water. Many were trapped within driftwood and even more were likely buried in the sand brought in by the surges. The spectacle of these bedraggled chicks suggested that thousands would perish as the temperature dropped overnight.
We visited the site following morning and, remarkably, found dry chicks in creches huddled within and close to driftwood, apparently none the worse for the previous evening’s traumas. Large numbers of adults had returned and some of these had relocated their chicks, presumably by their voices, and we saw some chicks being fed or given drinks. But washed eggs, many broken, and the corpses of hundreds of chicks were scattered among the deposited driftwood. We estimated that a few thousand must have been killed by the previous night’s events.
The following evening wave surges again reached the beach crest but did not extend into the colony.
While these events have been recorded before on Bird Island, the 24 July ingress of sea water into the edge of the Sooty Tern colony illustrated the vulnerability of the birds in this part of the colony, and of the island itself, to extreme climatic events. And before the strong winds of this south-east season wane there will be more spring tides around new and full moons (including a total lunar eclipse in Seychelles on 7 August), raising the possibility of more sea water incursions into the colony. The longer-term prospects of sea level rise and more violent storms are of huge concern to low lying islands like this corner of paradise and to the wildlife that inhabits them.