The Greenland White-fronted Goose Anser albifrons flavirostris

eeding geographical locations respectively.
Critical elements in the annual cycle can occur at
different places in time and space, and accordingly
factors that regulate the rate of change or
limit population size can affect population dynamics
in different places at different times. In
the case of the Greenland White-fronted Goose,
we begin to see that different mechanisms have
limited the size of the population in the very recent
past. This has either been through the maintenance
of low (relative to potential) annual survival
rates through hunting on the wintering
grounds, or through recent declines in fecundity
due to apparent restrictions of entry to breeding
age class (potentially through restrictions on prebreeding
condition of females). Hence, we have
seen a population that was maintained at a level
below its potential by hunting kill expand in response
to protection from winter hunting. The
present rate of population increase shows signs
of slowing in the last few years, despite no decrease
in annual adult survival, showing that
some other mechanism is responsible. This is due
to falling fecundity, with a stable number of breeding
pairs returning to wintering grounds with
young despite increasing population size. At one
wintering site, Wexford, this trend has ultimately
resulted in a decline in wintering numbers. This
may to some extent be the result of a run of summers
with low June temperatures. This may in
turn be a consequence of global climate change
that has made, and is predicted to continue to
make, summers in northern west Greenland
cooler in coming years. Hence this trend may become
manifest elsewhere if patterns of climate
change continue as predicted.
The conservation message from this type of study
is clear. We need to be able to understand the role
of different processes throughout the annual cycle
of such populations and we need to be able to
monitor these processes and their effects. It is
important to be able to establish which factors
affect a population in which ways and at which
periods in the annual life cycle. It is not enough
to establish patterns in survival and reproduction
at one wintering site and expect to be able to understand
the processes that shape the changes in
total numbers from year to year. Although it is
possible to make some inferences about the patterns
of population change, as is evident here, it
is not yet possible to demonstrate causal relationships.
Conservation needs more examples of
experimental manipulation of legislation and their
demographic repercussions on population change,
in order to be more confident in predicting the
effects of change. In fact, there exist very few good
examples of this (see Nelson & Bartonek 1990).
In North America, the implementation of adaptive
waterfowl management strategies ('wildlife
management by experimentation', MacNab 1983)
has met with mixed success (Johnson & Williams
1999). One major problem with, for example, attaining
the objective of determining the effects of
hunting harvest on annual survival has been the
conflict between maximising the hunt harvest and
maximising the knowledge derived from experimental
manipulation of the hunting bag. Nevertheless,
it is essential to understand the strength
of such processes, including, for example, the
strength of density dependence and the extent to
which differences in individual behaviour determines
the access of individuals to necessary nutrients.
It is also necessary to demonstrate the
extent to which hunting mortality is additive. If
it can be demonstrated that hunting mortality is
partially compensatory, sustainable hunting can
be maintained below a critical threshold without
seriously reducing total population size.
All these effects require monitoring of change in
numbers in the population as a whole, whether
this is achieved through annual winter census (including
proportions of young present to establish
breeding success and, by difference, survival),
or surveys of the pre-breeding, nesting or moulting
areas. It is essential that at least winter inventories
and measures of breeding success are maintained,
as these remain the only practicable means
of monitoring the numbers and breeding/survival
processes in the population. Although it is
difficult to maintain count coverage by observers
in remote areas (where conditions may be logistically
difficult), this remains the absolute priority
to extend the present time series. At the moment,
there are no attempts to carry out regular
aerial survey of spring staging, nesting and moulting
areas in Greenland, although all have been
carried out on a limited basis in the past. These
three periods are, as we have seen, critical ones
in the annual life cycle and regular (e.g. every five
years) survey of these would be highly desirable.
Such information might provide great insights
into the way local conditions (including local
goose densities) may affect dispersal, survival and
reproduction.
Nevertheless, if we are ever to be in a position to
interpret the reasons behind observed changes in
population changes, we must continue with the
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