Fróðskaparrit - 01.01.2001, Blaðsíða 124

128
BREEDING DISTRIBUTION AND NUMBERS
OF WREN (TROGLODYTES TROGLODYTES) IN THE FAROE ISLANDS
places where there were no rats and there-
fore no need to keep cats. Since then rnany
authors have emphasised the negative ef-
fects the presence of cats have on the abun-
dance of wrens in the islands (e.g. Miiller,
1862; Feilden, 1872; Andersen, 1898;
Klinckowstrom, 1911; Ferdinand, 1947;
Patursson, 1948; Williamson, 1948).
Besides scattered, short references to lo-
cal concentrations of breeding wrens no
quantitative studies have been made until
1981, when a census of the landbirds of the
entire Faroes, involving a large amount of
field-work, was conducted (Bloch, 1981).
With reference to the wren this census
yielded a total of 250 singing males and the
breeding population was estimated at 250-
500 pairs (Bloch and Sørensen, 1984); lat-
er this estimate was revised to 500 pairs, no
explanation given (Bloch et al., 1996).
During the past 20 years I have intermit-
tently been studying wrens in the Faroes.
The primary aim of the present account is
to estimate the size of the total breeding
population during this period (i.e. an over-
all average for the 1980s and 1990s) as well
as to describe the geographic distribution
and habitat-use. In addition, data on the
magnitude of annual fluctuations in num-
bers are given but will not be elaborated on
in this paper. Finally, possible long-term
changes are discussed.
The islands
The Faroe Islands, situated in the North At-
lantic between Shetland and Iceland, con-
sist of 18 islands (and some srnall islets),
separated by narrow sounds and short
stretches of water; the maximum W-E and
S-N distances are about 75 km and 115 km,
respectively (Fig. 1); the total land area is
1401 km2. The islands range in size frorn
0.7 (Lítla Dínrun) to 374 km2 (Streymoy)
and with the highest peak at 882 m a.s.l.
(about 2% of total area > 600 m), the north-
em parts of the archipelago being the most
mountainous. The coasts are rugged with
high, vertical sea cliffs on the W and N
sides of many islands, whereas on the E
sides the coastal cliffs are usually lower,
with sloping grasslands. Typical features of
the landscape are: the many small to large
crevices and gullies (gjáir, singul. gjógv)
that cut deep into the coastal and inland
cliffs and mountains, the ledges or ”steps”
(hamrar) caused by differences in the prop-
erties of the tuff and basalt series giving the
mountain sides a stratified appearance, and
the infields or "home fields” (bøur) with
their settlements. The infields encompass
the cultivated land surrounding the individ-
ual farmstead or larger settlements and are
usually encirclød by stone walls or modern
wire fences. The settleinents are almost in-
variably located by the sea, and the infields
stand out as habitat-islands covering a total
of about 7% of the Faroes (see Enckell et
al., 1987:Fig. 1). Within the infields the
vegetation is often relatively lush, as it is in
some sheltered sites such as in gjáir , on
cliff-shelves or in seabird colonies. Natural
shrubs or birch woods are absent, but on
some islands there are small plantations of
introduced coniferous and deciduous spe-
cies of trees; total area is about 100 ha. The
rest of the land consists of outfields (hagi)
extending from the shores to the mountain