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The Greenland White-fronted Goose Anser albifrons flavirostris

The Greenland White-fronted Goose Anser albifrons flavirostris

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more direct measures of 'body condition' in determining<br />

factors affecting individual performance.<br />

1.5 <strong>The</strong> flyway concept as related to<br />

<strong>Greenland</strong> <strong>White</strong>-<strong>fronted</strong> Geese and<br />

the format of this thesis<br />

<strong>The</strong> study of the <strong>Greenland</strong> <strong>White</strong>-<strong>fronted</strong> <strong>Goose</strong><br />

has never been a full time project for any of the<br />

characters involved. In Ireland, the National Parks<br />

& Wildlife Service has made a substantial annual<br />

commitment to research and survey of <strong>Greenland</strong><br />

<strong>White</strong>-<strong>fronted</strong> Geese since the 1960s, when counts<br />

and age ratio assessments were made at Wexford.<br />

In more recent years, the regular marking of a<br />

sample of individuals captured at Wexford and<br />

substantial effort invested in the resighting of<br />

these individuals has generated an impressive<br />

database of knowledge to support the international<br />

research and survey effort. However, elsewhere,<br />

the work has been carried out on an ad<br />

hoc basis, gathering data for differing purposes<br />

at different stages of the life cycle. <strong>The</strong> result is<br />

something of a ragbag of information, not always<br />

well inter-linked, and certainly never based upon<br />

a single research plan with well-defined targets<br />

and objectives. <strong>The</strong> available information is therefore<br />

scattered, and one purpose of this thesis is to<br />

draw together the disparate strands in order to<br />

determine what information is available and identify<br />

the gaps in the existing knowledge.<br />

Much of the reference material relating to <strong>Greenland</strong><br />

<strong>White</strong>-<strong>fronted</strong> Geese has been gathered in a<br />

recent review and need not be repeated here<br />

(MS24). This forms the background to the thesis,<br />

in the sense that many of the results of studies<br />

are summarised there. Chapter 1 establishes the<br />

setting for the thesis. <strong>The</strong>re follows a review of<br />

taxonomic relationships and the recent history of<br />

the <strong>Greenland</strong> <strong>White</strong>-<strong>fronted</strong> <strong>Goose</strong> that attempts<br />

to conclude something about the potential limits<br />

to this population (chapter 2). <strong>The</strong> following chapters<br />

explore the elements of the life cycle where<br />

critical factors may operate with respect to fecundity<br />

or survival. Outside the breeding areas, there<br />

are four periods of the annual life cycle when<br />

<strong>Greenland</strong> <strong>White</strong>-<strong>fronted</strong> Geese must accumulate<br />

stores in anticipation of long migratory flights.<br />

<strong>The</strong> population stops off in Iceland in spring and<br />

autumn en route to and from <strong>Greenland</strong>. <strong>The</strong> geese<br />

must accumulate energy stores enough to travel<br />

to and from Iceland and <strong>Greenland</strong>. Since spring<br />

acquisition of stores in anticipation of the spring<br />

flight to Iceland, and thence onward to <strong>Greenland</strong><br />

will also have consequences for reproduction,<br />

these two events in the annual life cycle have<br />

attracted considerable interest, and have separate<br />

chapters to themselves (chapters 3 and 4).<br />

On arrival in west <strong>Greenland</strong> after traversing the<br />

<strong>Greenland</strong> Ice Cap, the geese must again replenish<br />

depleted stores in preparation for the reproductive<br />

period. Geese were once thought to be<br />

largely capital breeders, investing stored nutrients<br />

in clutches and their incubation, although<br />

this view is increasingly challenged (see review<br />

in Meijer & Drent 1999). In the case of the <strong>White</strong><strong>fronted</strong><br />

<strong>Goose</strong>, it is now well demonstrated that<br />

females indulge in extended periods of pre-nesting<br />

feeding when birds can add substantially to<br />

their store of nutrients in readiness for egg-laying<br />

and incubation (chapter 5). For a population<br />

in which the reproductive success is well below<br />

the average for other populations of the same<br />

species, it is important to explore factors that may<br />

limit recruitment and reproductive output (chapter<br />

6). <strong>The</strong> period of flight feather moult represents<br />

a potentially critical period in annual cycle,<br />

since birds become flightless for several weeks,<br />

making them more vulnerable to predation and<br />

the depletion of local food resources until they<br />

regain the power of flight. <strong>The</strong> duration of moult<br />

and the period of pre-migration accumulation of<br />

stores in autumn are key elements in the annual<br />

cycle of the population (chapter 7).<br />

<strong>The</strong> return flight from <strong>Greenland</strong>, again stopping<br />

off in Iceland, has been little studied, although<br />

there remains the potential for occasional mass<br />

mortality associated with this migration episode<br />

(as well demonstrated for other goose populations,<br />

e.g. Owen & Black 1989, Boyd & Sigfusson<br />

in press). In comparison with high arctic forms,<br />

late summer and autumn are periods of plenty<br />

for <strong>Greenland</strong> <strong>White</strong>fronts, when food in <strong>Greenland</strong><br />

and Iceland is not especially limiting and<br />

the weather is rarely sufficiently severe to cause<br />

between year variation in adult annual survival.<br />

That said, there remains an autumn hunt of this<br />

population, involving some 2,900-3,200 birds shot<br />

every year in Iceland. This period remains a priority<br />

for future research.<br />

Having reached the overwintering habitat, it is<br />

important that this habitat is sufficient in quantity<br />

and quality to ensure survival. <strong>The</strong>re was<br />

considerable evidence that in the 1950s, habitat<br />

15

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