Fróðskaparrit - 01.01.2004, Side 260

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PHILOPATRY, DISPERSAL, AND SURVIVAL OF WREN
(TROGLODYTES TROGLODYTES) IN THE FAROE ISLANDS
the difference not being statistically signifi-
cant (Chi square = 2.38, df = 1, p>0.1). No
breeders were re-sighted > 1 km from the
ringing site.
Philopatry
The return rate of breeding males in the
year subsequent to ringing was higher than
for females (61.5% and 15.0%, respective-
ly) and all the re-sightings were made at the
place of ringing, or within a few hundred
metres. Besides, 8 of 9 fledglings (return
rate 10.2%) that were re-sighted in their
fírst breeding year were males returning to
their natal area, and assuming an equal sex-
ratio at fledging, the difference between
sexes was consistent with expectations
and statistically signifícant (Fisher's exact
test, 1-tail, z=1.81, p<0.05). Among these
one-year old males 5 were definitely paired
and the others were, with a high degree of
probability, not (two on Mykines and one
in Tjornuvík), whereas 15 of those that
were more than one year old were paired,
the difference being statistically significant
(Fisher's exact test, 2-tail, p<0.05).
Survival
Individuals not re-sighted in the following
year had either died or emigrated; hence
the return rates (Tab. 1) are equivalent to
minimum survival rates and when it is as
high as in the breeding males it is probably
close to the actual survival rate. Out of 16
breeding males being at least two years old
(i.e. ringed as breeders) 7 returned to breed
in the following year (i.e. 43.8%) and 3 out
of 7 (42.9%) being at least 3 years of age
returned, and 2 males were still alive at the
age of at least 5; thus 3 of 16 males were
faithful to the same area for at least 3 con-
secutive years (Tab. 2). Three of 5 males
known to be one year old (i.e. ringed as
fledlings) returned in the following year.
Thus, for males there is no clear indication
of minimum survival rate changing with
age after the fírst year, though the samples
are small and individuals ringed as breeders
form a heterogeneous group with respect
to age. For breeding males the calculated
mean life expectancy (using a maximum
annual mortality rate of 38.5% as suggested
by the return rate across years and study ar-
eas) is 2.1 years. As the wrens breed at the
age of one the mean longevity is 3.1 years.
The return rates for breeding females and
fledglings are far too low to reflect actual
survival rates.
Comparison between study areas
There are no discernible patterns or statis-
tically signifícant differences between Ihe
study areas with regard to return rates.
Discussion
The present study shows that most of the
autumn observations (45 of 134 marked in-
dividuals, i.e. 34%) were made within < 2
km of the breeding site which, of course,
was to be expected as sightings of marked
individuals beyond this distance were due
to mere chance and not the result of a sys-
tematic search. However, 4 yearlings (of
24 re-sighted in autumn) dispersed > 2 km
from their natal site during the autumn, but
all within the island. In one instance inter-
island movements occurred as a fledgling
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