The Greenland White-fronted Goose Anser albifrons flavirostris

9 Synthesis
9.1 Anticipatory acquisition of nutrients,
density dependence and constraints
upon fitness
In spring, every female Greenland White-fronted
Goose of breeding age must clear three nutritional
hurdles in order to breed successfully. The annual
cycle involves completion of two spring migration
episodes. Both require the bird to make the
necessary physiological and anatomical modifications
and lay down fuel reserves to sustain two
flights of 1,500 km, one over the sea to Iceland,
and the second crossing the sea and the Greenland
Ice Cap. The ease with which an individual
can clear these hurdles has various fitness consequences.
Failure to construct large enough flight
muscles or energy stores to sustain the flight will
result in death en route – this much natural selection
will ensure. However, the ability to accumulate
the necessary resources to only just complete
the two flights leaves no stores for investment in
reproduction. Slow accumulation of adequate
stores will delay departure from staging areas and
Lipid costs of egg laying and incubation
Costs � body
mass (kg)
BMR
(kJ)
Lipid equivalent
of 1xBMR
(g/day)
DEE
(xBMR)
time of arrival to the nesting grounds, so condition
mediated timing of breeding may also affect
reproductive output in this way. To complete the
journey to the breeding grounds early enough
with some extra stores remaining is likely to contribute
to the investment in reproduction, and
this, together with efficiency in finding food during
the pre-nesting period, is likely to determine,
to a major extent, the reproductive success of that
individual.
On the other hand, there must be some upper
limit on the amount of energy or other nutrient
stores, set by the cost of carrying such excess body
mass (e.g. predation risk and enhanced energy
use induced by heavier flying weight, see review
in Witter & Cuthill 1993). Nevertheless, the ability
to acquire specific nutrients to store for use at
key points in the winter and spring has consequences
for the ability of a bird to reproduce, or,
in the extreme, to survive each migration. The
efficiency (and therefore the rate) of accumulation
of such 'capital' through a series of acquisi-
Table 9.1. Protein and lipid energy requirements for a laying Greenland White-fronted Goose, her clutch of
3 or 6 eggs and subsequent incubation. Analysis follows methods of Meijer & Drent (1999), using Basal
Metabolic Rate estimated from the relationships for non-passerines derived by Aschoff & Pohl (1970), i.e.
BMR = 330.W 0.722 (where W = body weight in kg.) and based on the assumption that daily energy expenditure
(DEE) during laying is equivalent to 1.7 x BMR. Protein costs were calculated using the modified
formula of Robbins (1981) related to body weight according to the formula 2.68.W 0.75 g protein day -1 (see
Meijer & Drent 1999 for full explanation).
Laying/
incubation
period
(days)
Lipid used in
laying/
incubation
period
(g)
Lipid
used in
clutch
(g)
Total
minimum
and
minimum
lipid
investment
(g)
Laying 2.78 690 18.2 1.7 4-8 123.5-247.1 49-98 172.5-345.1
Incubation 2.78 690 18.2 1.1 26 519.6 519,6
Protein costs of egg-laying and incubation
Costs � body Maintenance Laying/ Protein used in Protein used in Total
mass (kg) protein incubation period laying/incubation clutch minimum
(g/day)
(days)
period (g)
(g)
and
minimum
protein
investment
(g)
Laying 2.78 5.7 4-8 23.1-46.2 56-112 79.1-158.2
Incubation 2.78 5.7 26 165.0 165.0
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