Fróðskaparrit - 01.01.2004, Page 247

EIN SØGULIG LÝSING AV BÚSETINGINI HJÁ GRÁSPURVANUM í FØROYUM
OG STØÐU HANSARA í DAG
245
Fig. 2. Cumulative
number of settlements
colonized (not
necessarily
permanently) by the
house sparrow in tlte
Faroe lslands.
est were found in Tórshavn (90 pairs/ km2),
Vágur (79), Runavík (78), Kollafjørður
(69), and Fuglafjørður (67). On Vágar,
Sandoy, and Borðoy (Klaksvík) the larger
settlements did not have densities exceed-
ing 50 pairs/ km2.
Discussion
The irregular pattern and spottiness of
first records cannot be easily recognized
as an expanding wave of invasion sweep-
ing over the Faroes but rather as a series
of forward leaps, a “jump-dispersal” gov-
erned by local conditions. Already within
a few years of its first landfall (1935-36)
the house sparrow had become established
on Suðuroy (early I940s) and soon there-
after also in several other far apart places
and islands: Tórshavn (1946), Svínoy and
Klaksvík (1944-46), and Fuglafjørður and
Norðragøta (1948-49). Morphometric stud-
ies of house sparrows from different parts of
the Faroes indicating differences in origin
lead Jensen and Kampp (1997) to suggest
that the colonization of the Faroes was the
result of two or three (and by implication
possibly more) immigrations. They also ar-
gue that the house sparrow seems reluctant
to cross even short stretches of water; e.g.
18 years elapsed between the colonization
of Tórshavn and Nólsoy separated by 6 km
of water and only one individual of more
than 800 house sparrows ringed on Nólsoy
has been recovered outside this island; fur-
thermore they referred to other factors de-
laying dispersal such as high mountains on
Suðuroy (Jensen and Kampp, 1997).
The first 4 birds that arrived on Suðuroy
in 1935-36 are reported to have come on-
board a ship (Williamson, 1945). Such un-
intentional human transportation of house
sparrows has previously been known to oc-
cur, e.g. in the colonization of northern Nor-
way (Lund, 1956) and as a case in point the
observation of a house sparrow on board a
ship in the North Sea (Reinsch, 1971). Such
dispersal could explain the relatively early
appearance of house sparrows in larger
harbours such as Tórshavn, Klaksvík, Fug-
lafjørður, and perhaps also Sørvágur. Be-