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The record of one breeding pair of Lesser Crested Terns
Sterna bengalensis in the Valli di Comacchio, on the southern Po
delta, Italy, during June 1985 stimulated us to investigate the status of the
species in the Western Mediterranean (Brichetti & Foschi 1985). Recent
sightings in the British Isles led Grant (1984) and Smart (1984) to write in British
Birds about the complex problem of the identification of the species.
The Lesser Crested Tern is distributed
unevenly from Australia to the Persian Gulfand the Red Sea. In the Mediterranean,
one colony was found in 1937 on a small island in the Gulf of Sirte off the
Libyan coast (Moltoni 1938) and, although it presumably stili exists (Bundy
1976), it has not been rechecked. In 1895, one breeding pair was noted on Nakle
Lake in the Lebanon (Benson 1970), while there were significant breeding
sightings in Tunisia in the first half of this century (Heim de Balsac &
Mayaud 1962).
In the Mediterranean during the past
five or six years, several instances of pure or mixed (with Sandwich Tern Sterna
sandvicensis breeding
pairs bave been recorded: Camargue, France, in 1971, an adult in nuptial plumage
was noted in a colony of Sandwich Terns (Isenmann 1972); Banc d’Arguin, France,
in 1974-75, one mixed breeding pair, and, from 1976 to 1983, one adult among a
colony of Sandwich Terns (Petit 1976; Campredon 1976; Dubois 1983); Ebro delta,
Spain, one breeding pair in 1979 (M. Chokomian, Ardeola 28: 159), a
territorial pair in 1981 (J. Liovera & M. A. Bieilsa) and, in 1985, two
breeding pairs (Ferrer 1986).
In Europe, in addition to the cases of
certain or probable breeding, there are other reports, both coastal (about 14,
in Great Britain, France, Italy, and Spain) and inland (Switzerland 1946 and
1977, and Austria 1980 and 1983). The July 1971 record in the Republic of
Ireland is still awaiting verification (P.J. Grant in
litt.).
In Italy, the presence of the species
was considered accidental until recently, with only two sightings, both in the
nineteenth century, in Sicily in 1833 and 1839 (Moiloni & Brichetti 1978).
Since 1982, however, observations have become more frequent in the Northern
Tyrrhenian Sea, in the Adriatic and in eastern Sicily. A pair incubated one egg
in Valli di Comacchio in June 1985 (plates 137 & 138) and again in May 1986.
Migration
and wintering
The migratory routes and wintering
zones of the Mediterranean population were little known until recently. The
autumn migration (August to October) occurs along the North African coast (Libya
to Morocco) in an east-west
direction towards the Strait of Gibraltar. Jacob (1983) observed a regular spring migration ofadults
(early May
to mid June) along the Algerian coast in an easterly direction, reversing to
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 The Gambia, peaking between November and mid April (Cramp 1985).
Recent and repeated winter observations
in Nigeria, in january 1982, both at the mouth of and along the last 10 km of
the Niger river, denote the existence of wintering zones farther south than
earlier believed (Frugis in Brichetti & Foschi 1985). As well as frequent
summering Lesser Crested Terns, a few wintering ones are occasionally observed
on the Mediterranean coasts of Morocco and Libya.
Two Lesser Crested Terns Sterna bengalensis with
Sandwich Terns S. sandvicensis, and Lesser Crested Tern Sterna bengalensis with Sandwich
Terns S. sandvicensis, Italy, June 1985(P.
Brichetti)
Identification
In addition to the problems of
identification discussed by Grant (1984) and the morphological characteristics
reported by Cramp (1985), out findings indicate that the combination of the
colour and shape of the bill and the grey tail and rump exclude the possibility
of confusion with other species, including Sandwich Tern with an anomalous bill
colour. Other distinguishing characteristics include the white area between the
base of the bill and the lower margin of the crown, this white area being larger
and less pointed than that of Sandwich Tern.
In the field, dimensions appear almost
identical to those of Sandwich Tern. The flight action resembles that of a small
tern, and the dark edges of the first four or five outer primaries are evident.
The voice is less harsh than that of Sandwich Tern.
The identification of this species is
covered more fully in the paper by S. J. M. Gantlett, illustrated by Alan Harris
(Brit. Birds 80: 257-276).
Status of Lesser Crested Tern Sterna bengalensis
in the Western Mediterranean and in Europe. Large dot breeding colony; small dots
single breeding
pairs; circle confirmed
or presumed mixed pairs Lesser Crested Tern-Sandwich Tern S. sandvicensis;
triangles accepted records; squares records still under
consideration; dotted line regular migration route, with numbers
indicating main passage months.
Acknowledgments
We
should like to thank P.J. Grant for his help and for information concerning
claims of Lesser Crested Tern in the British Isles; and also S. Frugis, C.
Iapichino, P. Isenmann, R. Pardo Gutierrez and G. Tsunis for supplying useful
information.
References
BENSON,
S. V. 1970. Birds of Lebanon and the Jordan Area. London.
BRICHETTI, P., & FOSCHI, U. F. 1985. Prima nidificazione di Sterna
del Ruppell (Sterna bengalensis) in Italia e attuale frequenza nel
Mediterraneo occidentale. Riv. Ital. Orn. 55:16 1-170.
BUNDY, G. 1976. The Birds of Libya. London.
CAMPREDON, P. 1976. Observations ornithologiques sur le Banc d’Arguin (Gironde).
Alauda 44: 441-455.
CRAMP, S. (ed.) 1985. The Birds of the Western Palearctic. vol. 4. Oxford.
DUBOIS, P. J. 1983. ‘European news’. Brit. Birds 76::568.
FERRER, X. 1986. Fluctuations of the gull and tern populations in the Ebro
Delta, NE Spain (1960-85). Summaries of Conference Papers First Mediterranean
Seabird Syrnposium Alghero. Medmaravis.
GRANT, P. J. 1984. Orange-billed large terns. Brit. Birds 77: 372-377.
HEIM DE BALSAC, H., & MAYAUD, N. 1962. Les Oiseaux de Nord-Ouest de I’Afrique.
Paris.
ISENMANN, P. 1972. Bemerkungen zur Beobachtung einer Sterna bengalensis
in der Camargue (Sudfrankreich). Ardea 60: 226-228.
JACOB, J. P. 1983. Oiseaux de mer de la cote centrale d’Algérie. Alauda
51: 48-63.
MOLTONI, E. 1938. Escursione ornitologica all’Isola degli Uccelli (Golfo della
Gran Sirte, Cirenaica). Riv. Ital. Orn. 8:1-16.
MOLTONI, E. & BRICHETTI, P. 1978. Elenco degli Uccelli italiani. Riv.
Ital.. Orn. 48: 65-142.
PETIT, P. 1976. Présence et nidification d’une Sterne voyageuse (Sterna
bengalensis) dans une colonie de Sterne caugek (Sterna sandvicensis)
sur le Banc d’Arguin (France). Ardea 64: 81.
SMART, M. 1984. Identification of Lesser Crested Tern and its status in the
western Mediterranean. Brit. Birds 77: 371-372.
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