After a poor year for Sooty Terns in 2015, possibly connected with the unusually warm surface water of the western tropical Indian Ocean at the time, 2016 is currently looking more promising. The earlier advent of the south-east trade winds, accompanied by a cooling of the sea surface, has led Sooty Terns to return and begin their nesting activities much earlier than in 2015. In these early June evenings the air is full of birds, many undertaking their rapid high flying courtship rituals, while those on the ground are displaying, copulating, making their shallow nest scrapes in the ground, and some females already laying their single eggs.
An approach via the inland path up the west coast exposes a walker to ever increasing noise of hundreds of thousands of birds, both in the air and on the ground. Those of us working in the colony have to wear ear protection as the noise level exceeds by a long way the EU’s safety limits.
Despite the number of birds already present, the colony is still in the very early stages of the annual breeding ritual and many birds have yet to arrive. But the number of eggs we find is increasing daily and within a few days the density of nests in many parts of the colony will exceed six per square metre. Incubating birds are as close together as they can be without infringing their neighbours’ space, and any birds that dare to attempt to enter another’s territory are viciously attacked.
The breeding season is prolonged as the parents incubate the egg for 28 days. After hatching, the chicks take a further 60 or so days before they flex their wings and fly. During this long period catastrophes can happen, as they did in both 2014 and 2015, with periods of food shortage leading adults to desert their eggs and chicks to die as the
parents failed to find food.
At its peak in late June and early July the Sooty Tern colony is one of the most spectacular sights the bird world can provide, and the Bird Island colony is the largest in the world that is easily accessible to tourists.