Náttúrufræðingurinn - 1999, Side 12

occupied territory, was used for calculations in
subsequent years.
Several people have hunted Ravens systeni-
atically in the study area. We have the total catch
of one of these hunters, Mr. Ingi Yngvason for
1981-1998 (in litt.). For other hunters we have
information for the period 1981-1991 (Kristinn
H. Skarphéðinsson etal. 1990, Wildlife Manage-
ment Institute, in iitt.).
The estimated size of the territorial popula-
tion was 88 pairs in 1981 (60% occupancy), but
only 58 pairs in 1998 (40% occupancy). Regres-
sion of territorial population over years gave a
highly significant negative trend (Fll7=24.5;
P<0.001, Fig. 3). The decrease in the size of the
territorial population amounts to 31% for 1981-
1998, or 2.1 % per annum.
A number of territories are now deserted, i.e.
have not been occupied for 5+ years. Deserted
territories are found all over the study area, but
are most common in the Mývatn area and the
highlands east of Lake Mývatn (Fig. 2) where
Ravens have been persecuted relentlessly during
the past two decades.
The percentage of occupied territories con-
taining breeding pairs was on the average 85%
(range 74-100%). Regression of this parameter
over years gave no significant trend (Ft n=0.14;
P=0.8). Nest success, i.e. the proportion of
pairs breeding and fledging at least one young,
was only measured in 1981-1985. On the aver-
age 20% of all nesting attempts failed, the main
cause being human interference. The estimated
total production of lledglings in study area fell
from 200 in 1981 to 120 in 1998, or40% (Table
1).
A minimum of 100-200 Ravens were killed
annually in the study area in 1981-1987, 200-
400 birds in 1988-1991, and c. 200 birds since
1992 (Table 2). The Raven catch increased c.
14% per annum in 1981-1991. From 1992 we
only have data available from Mr. Ingi
Yngvason, and his catch has been relatively con-
stant during this period. This data shows clearly
that for many years the Raven catch in the study
area has been greater than the estimated young
production of the local Raven population (Ta-
bles 1 & 2).
No studies have been done on whether the
Raven hunt has benefited the waterfowl
populations being protected with this action.
On the other hand, a decrease in the Raven popu-
lation could have negative effects on other organ-
isms. The Gyrfalcon Falco rusticolus popula-
tion in the study area uses mainly old Raven
stick nests for breeding (52% of all nest sites,
Cade et al. 1998). Some Gyrfalcon pairs now
have problcms finding suitablc nest sites on their
territories.
All wild birds in Iceland are protected by law
(Act no. 64/1994). According to the law the min-
ister of environment can allow hunting birds for
food or to prevent depredation, but this can only
be done on a sustainable basis. The Raven has
been regarded as a pest species, and there is no
closed season. Our studies show that Raven
hunting in Iceland is at present not in the spirit
of the law; it is not a sustainable harvest. In our
opinion this practise has to be terminated. One
possibility would be to restrict hunting to areas
where the Ravens cause damage, as at Eider colo-
nies and other waterfowl colonies like at Lake
Mývatn. Also, killing of Ravens should only be
allowed during the time of year when the birds
cause damage, e.g. the breeding season of the
waterfowl. At other times the Raven should be
protected.
PÓST- OG NETFÖNG HÖFUNDA/AuTHORs'
ADDRESS & E-MAIL
María Harðardóttir
ÓlafurK. Nielsen
Náttúrufræðistofnun íslands / Institute of
Natural History
Hlemmur3
P.O. Box 5320
lS-125Reykjavík
maria@ni.is
okn@ni.is
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