Fróðskaparrit - 01.01.2001, Blaðsíða 126

130
BREEDING DISTRIBUTION AND NUMBERS
OF WREN (TROGLODYTES TROGLODYTES) IN THE FAROEISLANDS
sea cliffs that are several hundred meters
high can usually be heard from a boat be-
low or from the top of the cliff, but the ex-
act positions of the individual males are of-
ten difficult to pinpoint. While the counts
from the infields, provided the circum-
stances {e.g. season, time of day, number of
visits, weather) during census-taking were
favourable, are considered reasonably ac-
curate, those from cliffs and some other
outfield sites are of unknown accuracy.
In addition to the plotting of singing
males, observations of fledged young (es-
pecially in July when the family still keeps
together and the food-begging youngs are
easily located) and single birds were also
noted.
In calculating the total numbers I have
simply added the estimates for each unit of
area. For places visited in two or more
years the estimate was given as the lowest
and highest numbers. A field-note saying
”at least 2 males” or 2+ was in the end put
down as 2-3 males. The final totals for the
islands and the Faroes are thus based on ob-
servations from different years and can be
seen as a sort of overall average for the past
20 years. The estimates are given as num-
ber of pairs, although the censuses mostly
refer to singing males and no corrections
for unpaired males (not uncommon) or
polygamous males (rarely found in the
Faroes; pers.obs.) have been made. All es-
timates are considered conservative.
Each plotted pair was assigned to one of
four habitats; viz. settlements, infields, out-
fields, and sea cliffs. The settlements, lo-
cated within the infields, may consist of
anything from a single farmstead or small
cluster of houses to a small village (< 50
houses) or a town (the largest, the capital
Tórshavn, has about 15000 inhabitants)
with gardens, sometimes small plantations,
a church and graveyard, patches of grass-
land, often a small stream coming down
from the hills, houses for stores, boats etc.
In this context the settlement habitat is re-
stricted to the built-up area. The infield
habitat is here defined as the cultivated land
surrounding the settlement often with some
solitary, old, sometimes delapidate houses
for sheep and cattle, barns and crofts made
of stones, or modem buildings made of
wood or concrete. The perimeter, and
boundary between infield and outfield, is
often a stone wall or modem sheep fence.
Parts of the infield are often intersected
with dykes. The outfields as a habitat cate-
gory are here defined as all areas outside
the infields, with vertical cliffs, gjáir,
mountain sides with ledges and screes and
often boulder-fields further down, steep
grassland slopes intersected with ravines
and small brooks, and some scattered hous-
es like those in the infield. The fourth habi-
tat, the sea cliffs, is defined as the more or
less vertical, in some places several hun-
dred meters high, cliffs facing the sea, with
ledges and crevices (incl. gjáir) and often
with numerous rocks and boulders above
the high-water mark. The habitat classifica-
tion adopted is based on the geographical
position of the birds rather than characteris-
tics assumed to fulfil the requirements of
the wrens. This was out of necessity since
time did not permit me to follow individu-
als long enough to assess the limits of their
territories.Thus, a number of border-cases