The Mediterranean's least known seabird - Lesser Crested Tern Sterna (Thallaseus) bengalensis
The Lesser Crested Tern with a total body length of about 37cm is a medium sized tern. It has a fast, graceful elegant flight. The mantle, rump and tail are of a pale blue-grey colour, contrasting with pale silvery-white primaries. The bill is slightly drooping, rather long, slender and orange in colour. This bird is very vociferous in the breeding colonies. Like most tern species the Lesser Crested frequents sea coasts and hardly ever ventures over land except in extreme cases such as when blown in by strong winds. This tern also avoids crossing open bodies of water and moves by hugging the coastline of different countries along its route to and from the breeding grounds.
The migratory routes and wintering zones of this unique Mediterranean population are still relatively unknown. A regular spring migration of adults (early May to mid June) takes places along the Moroccan, Algerian and Tunisian coast in an easterly direction, reversing to the west in the autumn (mid September to October), when presumed family groups of two to four individuals are recorded. Subsequently, movements occur along the Atlantic coasts in a southerly direction towards the wintering sites in Senegal and Gambia, peaking between November and mid April (Cramp 1985).
Repeated winter observations in Nigeria in January 1982, both at the mouth of and along the last 10 km of the Niger River reported the existence of wintering zones farther south than earlier believed. As well as frequent summering Lesser Crested Terns, a few wintering ones are occasionally observed on the Mediterranean coasts of Morocco and Libya.
Status and Distribution -
The Lesser Crested Tern is distributed unevenly from Australia to the Persian Gulf and the Red Sea. According to a report by Wetlands International (2000) it has a large global population estimated to be 180,000-210,000 individuals. Global population trends have not been quantified, but the species is not believed to approach the thresholds for the population decline criterion of the IUCN Red List (i.e. declining more than 30% in ten years or three generations). For these reasons, the species is evaluated as Least Concern.
Historical aspects of the Libyan colonies -
In the early 1930s the Italian hydrologist Giorgio Bini and his team paid four visits in two successive years to two offshore islands in the Gulf of Sirte, Libya; Legarah (Garah Island) and Hericha. Bini was of the opinion that it was Greek sponge divers or Arab fishermen who named Garah Island as Bird Island.
Bini’s first visit was reported as having taken place a couple of months prior to his December visit. Bini reports that during his second visit, in December he noted several hundred adult birds on the island. This is rather confusing as all adults are known to migrate west and out of the Mediterranean. In his third visit in July of the following year he found adults incubating eggs, while young chicks were present during his last visit in the following month (Bini 1935). The article was illustrated with six photographs showing adult birds in flight and on the island as well as groups of young birds (crèches). Bini erroneously recorded these terns as Caspian Terns Sterna caspia. Having read Bini’s report, the Italian ornithologist Edgardo Moltoni visited the island on 21 August 1937 and found a large colony of terns, but these were not Caspian Terns but the smaller Lesser Crested Tern, he estimated the colony in excess of 2000 birds, including adults and chicks.
In Birds of Libya, Bundy (1976) records the Lesser Crested Tern as common along the coast of Tripoli from west to east in June and less numerous, but not scarce from July to November. For Cyrenaica Bundy makes reference to Moltoni’s records. For over fifty years the island was forgotten by western ornithologists and it was fifty-six years after Moltoni’s visit that a team from the Working Group International Wader and Waterfowl Research (WIWO) and the Libyan Marine Biology Research Centre visited two islands reported in literature as hosting breeding Lesser Crested Terns. The colony on Geziret Garah was found to hold 1700 pairs and Geziret Al Elba, east of Garah island holding 40 pairs.
In August 2006 breeding was confirmed on the two known islands and a smaller colony on a man-made island in Lake Juliana, inside Benghazi lagoon, was discovered holding about 50 pairs in 2007.
Census of the breeding population
The first complete census of breeding Lesser Crested Terns was carried out from the 1st to the 7th August 2006. The second was carried out between in the first week of August 2007, and again in 2008. The team was made up of members from the Libyan Environment General Agency (EGA), University of Tripoli, Libya, RAC-SPA, Tunis, Istituto Nazzionale per la Fauna Selvatica (INFS), Italy, Tour du Valat (France), BirdLife Malta (BLM) and the National Museum of Natural History (NMNH) Malta. This year's mission will continue monitoring the populations as well as evaluating the possibilities of fitting geo-locators on adult birds to find out where they spend the winter months.