Fróðskaparrit - 01.07.2004, Síða 115

KYKSILVUR f FØROYUM - EIN GJØGNUMGONGD AV TØKUM DÁTUM
113
Species Hg Reference
Black guillemot, 15 ind., Jun.-Aug.1996, dorsal contours 3,4 ± 0,9* Olsen et al., 2003
Black guillemot, 5 ind., shaft, fifth primary, left wing 1974 2,8± 0,5 Appelquist et al., 1985
Black guillemot, 9 ind., 1909- 1949 1,8 Somer and Appelquist, 1974
Common guillemot, 12 ind., shaft, fifth primary, left wing 1973 1,21 ±0,07 Appelquist et al., 1985
*Exluded in this mean is one individual with mercury concentration above 20 mg/kg, while the concentration in all the others was below 5 mg/kg. The mean value including this outlier was 4,7 mg/kg. Table 12 Mercury in seabirds' feathers, in mg/kg.
mercury concentration in guillemots at ca
1900 were approx. 0,6 mg/kg and in 1973
approx. 1,1 mg/kg. In Table 12 summary
results of mercury in feather analyses are
presented, including those on black guille-
mot feathers samples from the summer of
1996 (adapted from Olsen et al., 2003). The
analyses of thel996 samples were done on
dorsal (from the back between the wings)
and ventral (from the body under the wing)
body contour feathers and with some down
in-between. Turning from analyses of in-
testinal organs to feathers (or hair) may
warrant access to samples even from pro-
tected birds because the sampling in itself
may be done without inflicting harm to the
bird, it is however essential to be able to
correlate the feather mercury concentration
to some concentration in the bird and there-
fore the livers were analysed in the same
birds (Olsen et al., 2003). The aim of the
study was thus to compare mercury in
feather sampled under the wings as is re-
garded as the place where some loss of cov-
er is presumed to inflict the least harm to a
living bird, to mercury in feather sampled
at the back, and to relate these to the liver
concentrations. Testing showed, that there
was no significant difference between the
median mercury concentrations in the dor-
sal feathers to the ventral ones2, but also
that the feather mercury concentration may
not be used to extrapolate to a liver mercury
concentration.
Comparisons with earlier analyses (So-
mer and Appelquist, 1974; Appelquist et
ai, 1985) are complicated by he fact that
the earlier analyses are done on primaries
i.e. the principal quills of a bird’s wing, and
even though the variability of mercury con-
centration among primaries are known for
black guillemot (Appelquist et al., 1984) it
still remains to describe the concentration
in primaries to that in body feathers. In
analyses on Bonaparte's gull a marked dif-
ference was found between mercury con-
centrations both within one individual
feather, but also among the various feather
types (Braune and Gaskin, 1987). In the
Bonaparte's gulls, the mercury concentra-
tion in body feathers were higher than in
primaries, but in a similar study then on
herring gulls (Larus argentatus) the oppo-
site was found (Lewis et al., 1993). Thus, a