Fróðskaparrit - 01.01.1998, Síða 162

168
CHANGES IN FAROESE SEABIRD POPULATIONS AND HUMAN IMPACT
In 1768 the brown rat arrived to the
Faroes. This indirect effect of man has cer-
tainly affected the bird populations in a neg-
ative way, especially the hole nesting speci-
es, storm petrels, manx shearwaters and
puffins. Storm petrels are now only found
on not rat-infested islands. The shearwaters
and puffms have now only small isolated
colonies on islands with rats while their
main colonies are on the rat free islands. It is
only a question of time when rats will be in-
troduced to other islands and this is now the
most serious manmade threat for the sea-
birds as the traffic between the islands is
increasing and so the risk of transferring the
rats. The most popular tourist boat trip is to
the bird cliffs of Vestmanna where the pop-
ulations of guillemots and kittiwakes have
shown a dramatic decline during the last 40
years and they have probably been negative-
ly affected by the tourist traffic during the
last 15 years. Therefore it is highly recom-
mended that the tourism planning take the
vulnerability of the seabirds into account.
A major change in the seabird history
was the settlement of the fulmar, which
started to breed here about 1816. Since then
the fulmar has gradually increased in num-
ber and is now the most common bird on
the islands, composing 50% of the total
Faroese seabird biomass followed by
puffins (23%), guillemots (16%) and kitti-
wakes (7%). The increase of the fulmar in
the North Atlantic has partly been sustained
by the offal from the increasing fishing
fleet. As the hunting of guillemots and
puffins has been restricted the fulmar has
become the most important fowl. About
50,000 to 100,000 youngs are taken for
food each year but the population seems
still to increase.
Data for the guillemot suggest that there
was a very sudden decline of immature
birds late in the 1950s, probably caused by
food shortage, which may even have result-
ed in a reduction of the time immature birds
spent in the colony. The breeding popula-
tion showed a more gradual decline. Since
1980 the guillemot has been legally protect-
ed during the breeding season and this was
followed by some stable years. But in the
late 1980s, there was a drastic decline in the
number of guillemots. The production of
young guillemots and puffms almost com-
pletely failed, while the production of gan-
nets and kittiwakes were probably unaffect-
ed. The most negatively affected seabird
during the last two decades is the common
tern, which experienced an 11 -year period
of breeding failure. During the same period,
late in the 1980s, the plankton productivity
and the recruitment of the major food
species for the guillemots and puffins de-
creased dramatically. Also the recruitment
and individual growth of other fish stocks
were reduced during these years. This situ-
ation is now improving. The guillemot
numbers are increasing as well as the breed-
ing success and the growth of the young
puffms. Concurrently, the plankton produc-
tivity and the recruitment and growth of
many fish stocks has increased substantial-
ly. The main reason for these changes is nat-
ural, and therefore quantitative studies of
the interrelation between seabirds, their
prey, and oceanographical changes are re-
quired as a basis for identifying the effect of
other factors, such as human influence.