Funding from French Guiana’s Regional Department of the Environment enabled a team of research scientists from the CNRS (French National Centre for Scientific Research) to study the flight techniques of magnificent frigatebirds on the islet of Grand Connétable*. To measure their movements, the frigatebirds were equipped with Argos tracking beacons and altimeters. Recordings showed that they could cover distances of over 200 kilometres and reach a height of 2,500 metres.

* research published in Nature, 421, 333-334, 23rd January 2003.

To achieve these results, the magnificent frigatebirds use rising air currents to save as much energy as possible as they fly.

Because their weight (between 1.2 and 1.5 kilos) is very low in relation to their wing surface (a wingspan of up to 2.4 metres), they can rise on these thermals while circling in the air. Then they glide down again until they reach the following air “lift”.

This flight technique limiting the physical efforts of the bird is like the one migratory birds use on their long trips over land. The difference is that migratory birds avoid flying over the sea because there are no thermals over the water in their latitudes.

However, in tropical regions, the sea is hot enough to produce thermals all the time. Living in these regions, frigatebirds take advantage of the thermals to fly day and night for several weeks.

Since its feathers are not waterproof, its legs too short and its feet not webbed (meaning it cannot take off from the sea), the frigatebird is unable to land on water or even dive to catch fish, so it has developed an original hunting technique. From the air, it identifies the turbulence produced by shoals of tuna or dolphins that are following fish or squid. To escape their undersea predators, the latter jump from the water. The frigatebird (which has approached the surface) catches them in flight. The method is well-known to fishermen: when they see frigatebirds flying low, they know that there are shoals of fish nearby.

The diet of magnificent frigatebirds has an effect on their young. Since they live in tropical regions where food is scarcer than in temperate zones, the parents bring a relatively small amount of food back to their chick (only one chick because they only lay one egg at a time). This means that the chick takes about a year to grow, longer than any other seabird. It is usual for the female to feed her chick for about ten months, although the father stops after a month.