The Greenland White-fronted Goose Anser albifrons flavirostris

7 Moult of flight feathers
7.1 Introduction
Considering the annual cycle of birds in the context
of periods of nutritional stress, the period of
replacement of the body plumage represents one
such stage. The maintenance of plumage has considerable
consequences for the individual, not just
in terms of flight and aerodynamic efficiency, but
also because feathers provide effective thermal
insulation and, in the case of waterbirds, buoyancy.
The Anatidae have evolved a pattern of replacement
of feathers throughout the annual cycle,
and indeed, ducks may have multiple
plumages and moult throughout the year. In
northern geese, replacement of feathers occurs
throughout the annual cycle, except during the
breeding period (e.g. Gates et al. 1993), although
it is the period of flightlessness during the postbreeding
phase which has attracted most research
attention (Hohman et al. 1992).
In common with most of the Anatidae, and all
northern-nesting geese, Greenland White-fronted
Geese shed their flight feathers simultaneously
and become flightless for a period of 3-4 weeks
(Belman 1981). Flightlessness constrains feeding
opportunities and denies flying as a means of
predator escape, hence it seems highly likely that
selection will have reduced the flightless period
as much as food resources and predation risk
would permit. Whether the flightless period represents
a period of stress (i.e. where the nutrient
demands of a bird exceed the supply derived from
ingestion, resulting in catabolism of body tissue
to meet that demand, sensu Ankney 1979) has
been the subject of considerable debate (see
Hohman et al. 1992). Hanson (1962) demonstrated
that captive Canada Geese, fed ad libidum throughout
wing moult, lost weight. Ankney (1979)
pointed out that goslings increase their body
weight 20 fold, grow leg and breast muscles and
ossify a skeleton to almost adult size and grow a
full set of body tail and flight feathers. Hence, he
considered that it would be surprising if adult
Lesser Snow Geese could not meet the nutrient
demands of wing moult over the same time period.
Nevertheless, Owen & Ogilvie (1979)
showed significant declines in body mass with
moult stage in Barnacle Geese in Svalbard
amongst adult males and yearling females. Gates
et al. (1993) demonstrated significant declines in
lipid reserves during wing moult in breeding females
and non-breeding Canada Geese, suggesting
that energy stores (i.e. nutrients accumulated
in advance of periods of demand, sensu van der
Meer & Piersma 1994) may be built up in advance
of wing moult. Non-breeding Greylag Geese
Anser anser moulting on the Danish island of
Saltholm selected the most protein rich food available
(Fox et al. 1998) and showed modifications
to their nitrogen metabolism (Fox & Kahlert 1999),
yet still lost 12-26% of their body weight (MS17).
Subsequent dissection of birds obtained at this
site throughout wing moult has shown that most
of this involves use of extensive abdominal, mesenteric
and sub-cutaneous fat deposits which are
completely depleted by the time flight feathers
are regrown (unpublished data). The study of van
Eerden et al. (1998) also demonstrated that Greylag
Geese moulting in the Netherlands could not
meet their daily energetic requirements during
moult. In combination with use of field scores of
abdominal profiles to assess declines in fat stores
(Owen 1981, Loonen et al. 1991), these authors
concluded that geese relied upon fat deposits to
meet their energy requirements during moult.
Analysis of stable isotope ratios in the new grown
feathers of the geese from Saltholm also suggest
strongly that some of the protein involved in
growth of feather tissue must originate from body
stores accumulated prior to the moult period (unpublished
data). Greylag Geese moulting in Iceland
do not show significant changes in body
mass during moult (A. Sigfusson & C. Mitchell
in litt.), hence, it seems that this species shows a
flexible response to nutrient acquisition and wing
moult, depending on local conditions.
Is wing moult a period of energetic stress (sensu
Ankney 1979) for the Greenland White-fronted
Goose? What do the geese do during moult? What
habitats are utilised? Are there any indications
that the nutrient requirements of the period and
finite habitat availability during this stage of the
annual cycle could create density dependent limitations
on the population in the future?
7.2Moulting distribution and habitat
The non-breeding element of the Greenland
White-fronted Goose population moults in close
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