After beginnings in the late 19th and early 20th centuries, bird ringing (“bird banding” in the Americas and Australia) has become a major tool in the study of the lives of birds worldwide, enabling investigators to discover if birds remain in one place or, if not, where they travel, what routes they take and when they move. Long term studies can discover how long birds live, at what age they start breeding and if they nest in the same place each year or move somewhere else. With birds that defend territories, we can discover the boundaries of a territory by watching where ringed birds interact with unringed neighbours (or the neighbour might be ringed with a different colour).
The use of rings for bird study came relatively late to Seychelles, but in the 1960s the acquisition of Cousin Island, by the International Council for Bird Preservation (now called BirdLife International), led to the initiation of ringing programmes on some endemic land birds and seabirds. This led to some findings that were remarkable at the time. For example, Tony Diamond discovered that Bridled Terns on Cousin Island bred every 8.5 months, rather than annually – we still don’t know why.
My own studies on Bird Island began in 1972 and involved ringing small numbers of both adults and chicks of Sooty Terns. These birds nest during the south-east trade wind period from roughly May to October. Towards the end of the breeding season of 1973 we ringed several thousand chicks. I returned to UK in November 1973 and during the depths of winter in Aberdeen in February 1974 I received a remarkable note from the British Trust for Ornithology (BTO), who run the British ringing scheme. A Sooty Tern that I had ringed as a chick on Bird Island on 17 July 1973 had been found alive, floating in the Edith River near Katherine, Northern Territory of Australia, on 13 January 1974; it died soon after its discovery. This is about 8,800 km from its birthplace!
We have subsequently had only a few more distant recoveries of Sooty Terns, three in southern India and Sri Lanka, and one on a Royal Navy ship off Somalia. Within Seychelles, however, recaptures of ringed Sooty Terns have shown that breeding adults sometimes switch nesting colonies, most likely due to human disturbance (especially collecting of their eggs for human consumption) in the colonies where they were first ringed. We have also discovered that most young birds do not breed until they are five years old, and that many Sooty Terns live for over 30 years.
In 1976, I had the opportunity to visit many of Seychelles’ southern islands during a cruise, funded by the National Geographic Society, in a yacht “Fandango”. During the cruise we ringed Sooty Terns on several islands where they were completing their breeding season. In the Amirantes island group we visited a small sand cay, Boudeuse, which housed a large colony of around 3000 pairs of nesting Masked Boobies, large members of the Gannet family. We camped overnight and caught and ringed 400 birds during darkness by dazzling them with torches. Over the following years two recoveries were reported through the BTO. One was found sick near Porbandar, Gujarat Province in northern India, abut 7,500 km north-east of Boudeuse. The other was recovered off D’Arros Island, only about 85 km north-east of Boudeuse, but the circumstances were amazing – the intact bird, complete with ring, was found in the stomach of a large fish, a Potato Grouper, which can grow to about 2.5 metres long and weigh up to 110 kg. We have no idea whether the bird was eaten alive during one of its deep dives, or whether it was already dead and had been scavenged by the fish.
Although there are now other ways of tracking bird movements and behaviour, using miniature electronic devices such as geolocators, GPS loggers and satellite-based tracking tags, bird ringing continues to generate valuable information for conservation and other scientific research, and represents a popular pastime for appropriately trained amateur bird enthusiasts who devote many hours to catching wild birds, and recording a wide variety of data on the birds that they ring.
And like me, for these dedicated people there is always the chance of receiving notification of an exciting new discovery!