The Greenland White-fronted Goose Anser albifrons flavirostris

limitation which operates during another stage of
the life cycle, until now relatively little studied.
9.4 Overview and future research
The freedom to fly gives long distance migratory
birds the opportunity to exploit distant nutrient
and energy sources in the course of their annual
cycle. In particular, given endogenous sources of
energy to sustain periods of flight, it enables organisms
to move between islands of abundant
food resources across large expanses of wholly
unsuitable habitat. At the same time, this very
mobility creates patterns of energy and nutrient
demands in the form of expensive migratory
costs, met from storage accumulated during times
of resource abundance. The synthesis presented
here is helpful in conceptualising the annual cycle
of the Greenland White-fronted Goose as a sequence
of discrete periods according to energy/
nutrient acquisition or demand. Typically, this relates
to periods of storage of energy and/or nutrients
followed by short bursts of use of accu-
Winter maintenance
Autumn migration to wintering grounds
Accumulation of stores in Iceland
Autumn migration to Iceland
Accumulationof stores in Greenland
Wing moult
Brood rearing
Incubation
Egg laying
Accumulation of stores in Greenland
Spring migration to Greenland
Accumulation of stores in Iceland
Spring migration to Iceland
Winter accumulation of stores
mulated stores (generally breeding events or migration
episodes). However, there are also periods
in the life cycle where extra demands (such
as wing moult, or defence of body condition in
early to mid-winter) can be met by exogenous
supply (Figure 9.4).
It has frequently been asserted that evolution has
minimised the overlap of energy- and nutrientdemanding
periods of the life cycle of birds (the
“staggered costs” hypothesis coined by Lovvorn
& Barzen 1988). In the Greenland White-fronted
Goose, this separation in time and space offers
the possibility to specifically identify critical periods
in the annual cycle. In this way, it is possible
to assess the ability of individuals to reach
critical condition thresholds in order to meet each
of the specific demands they face in discrete periods
within the annual cycle.
From the nature conservation and research standpoint,
such an opportunity is fortunate in offering
a framework by which to concentrate future
study efforts. For each period of accumulation of
J F M A M J J A S O N D
Figure 9.4. The annual cycle of an adult breeding female Greenland White-fronted Goose represented as a
sequence of discrete calendar events, categorised as a series of periods of energy/nutrient acquisition or demand.
These generally fall into three categories: (i) Periods of storage of energy and/or nutrients (shown crosshatched
in the bars above). (ii) Use of accumulated stores (generally breeding events or migration episodes,
shown as dark bars). (iii) Periods in the life cycle where extra demands can apparently be met by exogenous
supply (such as during wing moult, brood rearing or the defence of body condition in early to mid-winter,
shown as shaded bars). Note that the period of brood rearing also represents a critical period for the female,
during which she must recoup depleted stores and potentially reserves utilised during brood laying and incubation.
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