Sternula albifrons
Sternula albifrons
The little tern (Sternula albifrons, Pallas, 1764) is a bird belonging to the Laridae family.
Systematics –
From the systematic point of view it belongs to the Eukaryota Domain, Animalia Kingdom, Phylum Chordata, Subphylum Vertebrata, Superclasse Tetrapoda, Aves Class, Neornithes Subclass, Charadriiformes Order, Lari Suborder, Laridae Family, Sterninae Subfamily and therefore to the Sternula Genus and to the S. albifrons Species .
The term is synonymous:
– Sterna albifrons (Pallas, 1764).
Within this species, three subspecies with different geographical distribution are recognized:
– Sternula albifrons albifrons; nominal subspecies, present in Europe, North Africa and the Middle East;
– Sternula albifrons guineae; with populations present in central and western Africa;
– Sternula albifrons sinensis; present in an area ranging from eastern Asia to the western coasts of Australia.
Geographic Distribution and Habitat –
The little tern is a bird which, excluding the American continent, is widespread throughout the rest of the world.
It is present in Italy where it nests in brackish water marshes, salt marshes and lagoons, but always near the water.
Description –
The Sternula albifrons is a bird that is recognized for having a length: 21-24 cm, with a wingspan of 48-52 cm, without sexual dimorphism; in fact both males and females, in addition to having the same characteristics, weigh between 50 and 65 grams.
The adults, in the summer period, have the upper parts, wings included, of a light gray color, with a blackish area restricted to the wing tips. The rump is whitish. The vertex is black up to the nape, while the forehead is white.
A thin black line then starts from the beak which reaches the eye and joins the black vertex. The cheeks, throat, chest and abdomen, including the lower parts of the wings, are white in color. The beak is yellow with a black tip and the legs are yellow tending to orange.
In the winter period the livery changes appearance and in this period the white area on the forehead extends more towards the apex and the black line starting from the beak disappears. The black part of the vertex also extends a little towards the ears. The beak is black and the legs tend to vary in color from yellowish to light brown.
The young resemble the adults in winter dress, however, having gray upper parts with evident brown and blackish stripes. The beak also has a little yellow-green at the base.
Biology –
The Sternula albifrons is a bird that nests on the coasts and in the inland wetlands of temperate and tropical Eurasia.
The mating phase is also preceded by the offering of fish by the male to the female, which is part of their courtship ritual.
The nesting takes place in small colonies present on the sandy beaches.
Both the male and the female hatch the eggs which are laid for a variable number from 1 to 4 per litter. The hatching period varies from 17 to 22 days.
Like other birds of the same genus, it is aggressive in defending the nest and chicks and attacks intruders who approach them.
Ecological Role –
The little tern is a species, which with its subspecies, migrates to spend the winter in the tropical and subtropical oceans, reaching South Africa and Australia
Its usual habitat is in open areas, on coastal or continental sandy beaches.
Its diet is based on fish, crustaceans and insects that it fishes by diving into the water, generally in saline environments.
The population of this bird is in decline although still, according to the IUCN, of minimal concern.
The main threats are related to the transformation of the nesting and feeding habitat and to anthropic disturbance in the nesting sites.
Sternula albifrons is one of the species to which the Afro-Eurasian Migratory Birds Conservation Treaty (AEWA) applies.
It is also listed in Annex I of the Birds Directive (79/409 / EEC).
Guido Bissanti
Sources
– Wikipedia, the free encyclopedia.
– C. Battisti, D. Taffon, F. Giucca, 2008. Atlas of nesting birds, Gangemi Editore, Rome.
– L. Svensson, K. Mullarney, D. Zetterstrom, 1999. Guide to the birds of Europe, North Africa and the Near East, Harper Collins Publisher, UK.