Fróðskaparrit - 01.01.2004, Page 261

HVUSSU MÚSABRÓÐIR (TROGLODYTES TROGLODYTES) YVIRLIVIR,
SPJAÐIR SEG OG HVUSSU STAÐBUNDIN HANN ER í FØROYUM
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Table 2. Number of individual wrens re-sighted in the same area for one or several years following year of
rínging.
Age and sex at time Number of Number of individuals and years of
of ringing (year n) individuals re-sightings
re-sighted n+1 n+2 n+3 n+4
Breeding males 16 9 4 1 2
Breeding females 3 1 2
Fledged males 8 5 2 1
Fledged female 1 1
ringed on Mykines and re-sighted on Nól-
soy must have passed over two or more is-
lands and made at least three sea-crossings
C’hard edges” sensu Wiens et al., 1985),
each 2-7 km wide. Thus, in the present
study 24 (27.3%, n=88) of the fledglings
were re-sighted in autumn close to their
natal site (Tab. 1). This is a high figure
compared to a Dutch study where 5.1%
(n=195) of nestlings ringed were seen in
the following winter (Kluijvercra/., 1940),
and English studies (few nestlings ringed)
where none was seen again (Armstrong
and Whitehouse, 1977). Hence, the Faroese
wrens seem more strongly attached to their
natal areas than than mainland ones.
A significant result is that male breeders
are considerably more philopatric than fe-
males; whether this also holds for yearlings
as the male-biased return rates suggest (Tab.
1) depends on the validity of the assumed
equal sex ratio in fledglings. As the degree
of philopatry is a function of annual survival
rate it is markedly higher than the observed
return rates. Analyses of English ringing re-
coveries show that overall annual survival
rate is approx. 37% (Hawthorn and Mead,
1975) and for adults 42% (Innis, cited by
Cramp, 1988). This is almost identical with
the 41% overall minimum survival of adult
(both sexes combined) Faroese wrens. Al-
though breeding females invest more ener-
gy in the breeding efforts and therefore may
have a lower rate of survival than males, the
high overall frequency (61.5%) of marked
breeding males re-sighted in the following
year suggests that the annual survival rate
is significantly higher in the Faroes than in
England. This, of course, has implications
for the actual degree of philopatry (i.e. per-
centage returning of those alive), which
among Faroese breeding males might be
well over 90%. As to breeding females,
the degree of actual philopatry is undoubt-
edly considerably higher than the observed
return rate, but not high enough to invali-
date the significant difference between the
sexes. Other studies have demonstrated
much lower degrees of site fidelity, though
in a study in England at least 40% of the
birds returned to the same winter quarters
in successive years (Hawthorn et al., 1971).