The Greenland White-fronted Goose Anser albifrons flavirostris

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7.4 Limits to suitable moulting habitat and potential inter-specific competition in the future Since the mid-1980s, Greenland White-fronted Geese have faced a major change at their moulting sites. Canada Geese Branta canadensis interior have become established as a common breeding bird in areas of west Greenland previously only exploited by Greenland White-fronted Geese (MS13). Resightings and recoveries from ringed birds have shown that these geese winter in the eastern United States, from Massachusetts and Connecticut south to Delaware and probably originated from the Ungava Bay population of Canada Geese that breed in northern Quebec (MS22). The Canada Geese arrive in late May and commence nesting in habitats close to open water, so that there appears little competition in time and space for breeding habitat between this species and the Whitefront. However, during the moult, White-fronted and Canada Geese use the same habitats and areas to regrow flight feathers. At this time, both species are largely confined to areas within 50 m of open water. During this phase in the life cycle, increased nutrient demands and enhanced predation risk means there is an increased potential for direct competitive effects. In sympatric situations, the diet of White-fronted Geese showed high niche overlap with the colonising species and included higher levels of poor quality bryophytes than at moult sites from which Canadas were absent (Jarrett 1999, Kristiansen & Jarrett in Kristiansen 2001). Faecal analysis suggested that Canada Geese had a broad dietary range which changed little between sympatric and allopatric sites; in contrast, allopatric Whitefronts showed very narrow niche breadth scores based on faecal content, suggesting this species is a specialist grazer (Kristiansen 1997, Jarrett 1999, Kristiansen & Jarrett in Kristiansen 2001). It would therefore appear that Whitefronts coexisting with Canadas switched to a more generalised diet, perhaps in response to competition from Canada Geese for favoured food items. The two species appeared to segregate where they occurred together. In 45 agonistic interactions between the species, Canada Geese won on every occasion, even when outnumbered. As a consequence, Whitefronts would stop feeding and adopt alert postures when Canada Geese approached to within 3 metres (Jarrett 1999). In a study area in Isunngua, numbers of both Whitefronted and Canada Geese increased from 1988, but in the mid 1990s, Greenland Whitefronts be- 62 gan to decline, and have disappeared as moulting birds from many lakes favoured in this area where Canada now predominate. The results from extensive studies are about to be published (Kristiansen & Jarrett in Kristiansen 2001). However, the implication from this study of a small area was that Whitefronts forced to moult with Canada Geese may be subject to exploitative competition as favoured plants are eaten out and interference competition when the dominant species physically prevent them from accessing potential feeding areas. Data from the 1999 aerial survey suggest that although both species showed highest densities in the same Kangerlussuaq region, at a local scale the two species were less likely to occur together than would be expected by chance (MS23). Whether this is a consequence of 'avoidance' competition or active exclusion remains conjecture. 7.5 Conclusions and discussion The few studies of moulting Greenland Whitefronted Geese suggest that these birds show no anticipatory accumulation of fat stores in preparation for moult. Rather, they shed and regrow flight feathers at their lowest level of annual body mass (equivalent to mid-winter minimum body mass). Since most studied northern and arctic geese show similar patterns, it is inferred that Greenland Whitefronts can derive all the necessary energy and protein required to complete the moult from exogenous sources. This suggests that under studied circumstances, moult habitat was not then limiting. On the other hand, the confinement of moulting birds to the proximity of open water from which they can escape terrestrial predators inevitably constrains the amount of exploitable habitat available to flightless geese. This has been found to equate to a potential feeding zone of at most 150 m from water in other species (e.g. Madsen & Mortensen 1987, Kahlert et al. 1996) and possibly less than 50 m in Greenland Whitefronts (Kristiansen & Jarrett in Kristiansen 2001). This particular spatial limitation on foraging at this stage of the annual cycle suggests that this is a potential limitation on habitat availability on the summering areas. In July, the moulting geese are confined to parts of the landscape adjacent to water bodies to which they can escape to evade predators. The amount
of available fresh green growth of graminoid plants with high protein at this time is limited in the landscape as a whole and dependent upon patterns of thaw. Global climate change could potentially interfere with the complex thaw gradients that ensure a sequence of protein rich food is available. Increases in White-fronted and Canada Goose numbers could also reduce available food resources to a level where nutrient availability could limit the numbers of moulting geese able to replace flight feathers on individual sites. Studies of moult, it’s precise physiology, the interplay between diet and behaviour need to be carried out in different parts of the range if we are to determine whether these various factors may limit nutrient acquisition and affect the population in due course. 63
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Contents Summary ..................
Page 7 and 8:
Summary The Greenland White-fronted
Page 9 and 10:
Greenland White-fronted Geese are u
Page 11 and 12:
Dansk resumé Den grønlandske blis
Page 13 and 14: 1 Introduction 1.1 Why Greenland Wh
Page 15 and 16: The Greenland White-fronted Goose i
Page 17 and 18: more direct measures of 'body condi
Page 19 and 20: 2Limits to population size in recen
Page 21 and 22: Despite the morphological similarit
Page 23 and 24: Scotland, the wettest peat soils we
Page 25 and 26: of this goose population. At the sa
Page 27 and 28: Spring count 16000 12000 8000 4000
Page 29 and 30: 3 Accumulation of body stores and t
Page 31 and 32: Body mass (g) 3500 3000 2500 adult
Page 33 and 34: h -1 and none showed any sign of re
Page 35 and 36: labelled water), the precise extent
Page 37 and 38: 4 Spring staging in Iceland and the
Page 39 and 40: Body mass (g) Body mass (g) 4000 35
Page 41 and 42: Goose droppings/m 2 6 5 4 3 2 1 0 P
Page 43 and 44: er 3KJ was a behaviourally dominant
Page 45 and 46: 5 Pre-nesting feeding 5.1 Introduct
Page 47 and 48: imagery and searches in helicopters
Page 49 and 50: 6 Reproduction 6.1 Breeding distrib
Page 51 and 52: predicted that at the end of this p
Page 53 and 54: Percentage of juveniles Figure 6.1.
Page 55 and 56: Mean age of first breeding 8 7 6 5
Page 57 and 58: periods in each winter as the exten
Page 59 and 60: Geese, it might be expected that in
Page 61 and 62: 7 Moult of flight feathers 7.1 Intr
Page 63: mass at different stages of regrowt
Page 67 and 68: 8 Survival 8.1 Introduction Almost
Page 69 and 70: the hunting mortality rate K t for
Page 71 and 72: during the period when the populati
Page 73 and 74: lands. This process was certainly u
Page 75 and 76: 9 Synthesis 9.1 Anticipatory acquis
Page 77 and 78: Mass based on API scores 3600 3200
Page 79 and 80: social system has traditionally reg
Page 81 and 82: ers (J. Madsen unpubl. data). In th
Page 83 and 84: limitation which operates during an
Page 85 and 86: NUTRIENT & ENERGY ACCUMULATION RATE
Page 87 and 88: eeding geographical locations respe
Page 89 and 90: 10 Acknowledgements A thesis is sup
Page 91 and 92: mark and to Ebbe Bøgebjerg for the
Page 93 and 94: L. Kramer, J.N. Kristiansen, T. Lai
Page 95 and 96: Marked Individuals in the Study of
Page 97 and 98: mussels, Mytilus edulis. Journal of
Page 99 and 100: Nichols, J.D. (1991) Extensive moni
Page 101 and 102: Thompson, S.C. & Raveling, D.G. (19
Page 103 and 104: 12Appended manuscripts 1: Fox, A.D.
Page 105: National Environmental Research Ins
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The Greenland White-fronted Goose Anser albifrons flavirostris

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