Yesterday evening we undertook our first search for Sooty Terns that we have ringed in the past, on Bird Island and in other colonies in Seychelles, beginning in 1972. Searching for ringed birds involves walking very slowly among the nesting birds, looking for birds with small metal rings that are individually numbered. By catching these birds in small nets we can record the numbers and look at the birds’ histories in a database. The search is very demanding and tiring but the results make it all worthwhile. Past work has shown that Bird Island’s Sooty Terns do not begin breeding until they are five years old and that adults live a long time. One exceptional bird was 38 years old but several have been recorded at over 30 years old. We have ringed Sooty Terns on many of Seychelles’ islands and this ringing has shown that some birds do move between islands. Such moves are stimulated by disturbance, especially the collection of their eggs, which are regarded as a delicacy by Seychellois.
During this evening’s search we found that while many birds already have eggs, most have not yet laid. These birds are currently displaying, especially using a “parade” display in which birds walk parallel to each other, or in opposite directions in a circle, with their necks extended and turned slightly away from each other. Most eggs are laid in the afternoon, between 1 and 4 pm, and we found many birds that had just laid, with both members of the pair together at the nest for some times before one of them would depart to feed while the other, usually the male, remains to incubate the egg.
In addition, we have marked 20 nest sites and caught and ringed one of the birds at each site to see for how long each member of the pair incubates while its mate lives at seas searching for food.
This will give us some idea how abundant their food supplies are this year.
So, we have made a start and look forward to discovering more about the lives of these fascinating birds as the this year’s breeding season progresses.