Fróðskaparrit - 01.07.2004, Blaðsíða 84

82
MERCURY IN LIVER, EGGS AND FEATHER OF BLACK GUILLEMOT
CEPPHUS GRYLLE FAEROENSISIN THE FAROE ISLANDS
mercury concentration in going from 1,8
mg/kg in the first half of the twentieth cen-
tury, to approx. 2,77 mg/kg in 1974. One of
these studies showed that the mercury con-
centration in black guillemot primaries was
lowest in the first primary on the right wing
and that the fifth and tenth primaries on
both wings were higher and rather similar
in mercury concentration (Appelquist et
al., 1984), and that similar results were
seen for guillemots in the North Baltic.
Findings of consistent high mercury con-
centration in the first primaries moulted
were reported for a number of seabird
species with different migratory habits
(Furness et al., 1986), and in the same
study, as well as in one by Lewis et al.
(1993), it was found that the mercury con-
centration in body feathers was consistent-
ly lower, of varying degree, and with less
variability than that of the primaries. In the
present study mercury was analysed in
body feathers, and even though it was
found that the mercury concentration in
body feathers at two different sites was
equal, it is reasonable to assume that the
difference observed in several other seabird
species between mercury in primaries and
body feathers, may also be found in black
guillemots. Given that in black guillemots
in the Faroes primaries are the first feathers
to moult after the fish-season (Asbirk,
1977; Dam, 1998b), it is plausible that also
the primaries in this bird will be higher than
in the body feathers sampled in the summer
months which had grown during late win-
ter, at a time when the diet mainly has been
dominated by crustacean and molluscs
(Dam, 2000). It could be tempting to per-
form a direct extrapolation of the results of
other seabirds to black guillemots, but it is
hardly worthwhile because the details in
moulting and foraging area as well as diet
choice, all factors which are known to in-
fluence the body mercury pool, would have
to be taken into consideration for such ex-
trapolation. Thus it is recommended that
comparative analyses of mercury are un-
dertaken on primaries and body feathers
from black guillemots in the Faroe Islands
for the purpose of continuing the time-trend
established by Appelquist et al. (1985). But
prior to this, however, one should deter-
mine whether there are differences in the
primary mercury concentration among the
sexes as was found to be the case for her-
ring gulls (Lewis et al., 1993), in which
case it will only be possible to track histor-
ical changes if details of specimen sex are
known.
Acknowledgement
Funding provided by the Nordic Council of
Ministers through the Working group of
Environmental monitoring and data and
from the Danish Ministry of Environment
through the DANCEA fund, The Arctic En-
vironmental Programme, is gratefully ac-
knowledged.
Several people have been involved in the
project, we would especially like to thank
those who did the field sampling; Marnar
Gaard, Eyðfinnur Stefansson, Bjørn Paturs-
son and Jóannes Mikkelsen.
The project had shooting permission
from the Faroese authorities