Fróðskaparrit - 01.01.2004, Page 264

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PHILOPATRY, DISPERSAL, AND SURVIVAL OF WREN
(TROGLODYTES TROGLODYTES) 1N THE FAROE ISLANDS
exhibit breeding site fidelity, a majority
disperse at the end of the breeding season
and spend the non-breeding season in, or
moving between, any places where condi-
tions are favourable and in the spring mate
some distance from natal areas. The islands
appear to be saturated with suitable breed-
ing habitats and territorial wrens (Bengt-
son, 2001 and unpubl.), which may result
in a lower site attachment in the females.
Ecological constraints on dispersal and the
benefits of philopatry may interact (Koenig
et al., 1992; Ernlen, 1994) and variation in
quality between territories may promote
variability in dispersing behaviour (Kokko
and Lundberg, 2001). Hence a justification
for comparing study areas, though the fail-
ure to detect any differences between them
with respect to dispersal patterns was not
surprising considering the small sample
sizes.
Conclusions
In the Faroes, wrens disperse in autumn and
during the non-breeding season they occur
in habitats not suitable for breeding, for in-
stance the littoral zone. However, the post-
breeding movements seem mostly confined
to the natal island, though at least one of the
colour-marked fledglings dispersed at least
50 km and passed several islands and open
water crossings. Dispersal is sex-biased
and relatively few adult females returned to
the areas where they had bred in the previ-
ous year, while the males, which are ter-
ritorial through most of the year, showed a
high degree of philopatry. Males breeding
for the first time also show a stronger at-
tachment to their nalal areas than females,
but appeared to be less successful in obtain-
ing mates than older males were. Mean an-
nual survival rate, and thus length of life
span, appears to be higher than in mainland
wrens. Evolutionary explanations for the
patterns observed require larger samples,
extended study areas, more behavioural ob-
servations during critical periods of time,
and experimental approaches.
Acknowledgements
Funding was received from the Swedish Natural Science
Research Council, Dansk-svensk samfunds fond for
kulturoch vetenskap, Copenhagen, Kungl. Fysiografiska
Sallskapet i Lund, and Letterstedska foreningen,
Stockholm. Among many local people and others who
provided valuable assistance the following deserve
special mentioning: Professor Dorete Bloch and her late
husband Hans Ólavus Danielsen, Mr Søren Sørensen,
Professor Arne Nørrevang, Ms Herdis Joensen, Dr. Pehr
H. Enckell, and the ringing-team in 1984, viz. Andrew
Berry, Tim Anderson, and Chris Dee.
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