Survival and dispersal in a new Barnacle Goose population 73
©Wildfowl & Wetlands Trust
Wildfowl
(2013) 63: 72–89
capture-recapture framework, where the
probability of survival can be estimated
separately from the probability of re-sighting
in series of repeated observations of
individuals (Lebreton
et al
. 1992; White &
Burnham 1999). However, survival studies
are particularly sensitive to biases in re-
sighting probabilities. For example, survival
estimates from pure re-sighting studies may
be substantially negatively biased because of
permanent emigration of individuals outside
the study area. Using both capture–recapture
and mark–recovery data in the same multi-
state models allows a more efficient use of
all available data and reduces this bias
(Duriez
et al
. 2009; le Gouar
et al
. 2011).
Dispersal is often difficult to study
because dispersing individuals potentially
can settle anywhere outside the study area
where suitable habitat exists (van Noordwijk
1995). Most dispersal studies therefore
focus on local movements between study
plots, and ignore longer distance dispersal.
Colonial-breeding birds such as Barnacle
Geese
Branta leucopsis
are highly suitable for
the study of dispersal, because their
colonies are discrete, often conspicuous, and
comparatively easy to monitor, so dispersers
can be clearly identified (Pradel 1996).
Another way of quantifying dispersal in
colonial birds is to assume, for individuals
known to be alive and at breeding age, yet
known not to be in a colony in the study
area, that those birds have dispersed (van
der Jeugd 2001).
Here we study survival and dispersal in a
recently-established temperate Barnacle
Goose population, which breeds in the
southwest of the Netherlands. Reliable
estimates of important population
parameters and their variation are needed to
predict the future development of this
population, to explore the potential effects
of various management scenarios, and to
evaluate the effects of measures that are
taken to mitigate conflicts. The Barnacle
Goose has long been considered a high-
Arctic breeding species, benefiting from the
short but productive Arctic summer at
the cost of a long migration and
potentially severe environmental conditions
encountered particularly at the start and end
of the breeding season. However, during the
last decades, it has rapidly adapted to a wide
range of habitats in the temperate zone,
thereby considerably shortening the
migration route, or even giving up migration
altogether (van der Jeugd
et al
. 2009).
Methods
Ringing, resighting and recovery data
Ringing and ring re-sightings data for 804
Barnacle Geese caught and colour-marked
as breeding birds in the Netherlands from
2004–2010 inclusive were used in the
analyses. Birds were rounded up during the
annual moult in July at Hellegatsplaten (at
the east end of Goeree-Overflakkee Island,
Delta area; 51°42’N, 4°22’E) in 2004 and
2005, at Krammerse Slikken (in the
southeast of Goeree-Overflakkee Island,
Delta area; 51°40’N, 4°14’E) in 2007, 2008
and 2010 and at Jan Durkspolder (Alde
Feanen, Fryslân; 53°07’N, 5°57’E) in 2009.
In total, 804 individuals were colour-ringed
(Table 1). Most of the birds were ringed in
the northern part of the Dutch delta area,
where most of the colonies of Barnacle
Geese breeding in the Netherlands are
