The Greenland White-fronted Goose Anser albifrons flavirostris

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Estimated annual juvenile survival rate niles marked in the previous winter were ever reported again, a remarkably low annual return rate (21%). One of them was reported from Pennsylvania, in the eastern United States in December 1990. It may be that the low survival rate that season was due to geese encountering severe weather (for example a storm in autumn 1990 that blew them westwards off track). The Lamb daily classification of weather systems over the British Isles for that period shows no obvious anomalies that could account for this extraordinary loss (H. Boyd. in litt.) Based on these two years, there is no evidence from the probability of birds shifting from Wex- 70 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 1982 1984 1986 1988 1990 1992 1994 1996 1998 Figure 8.4. Annual juvenile survival rate (± 95% CL) for Greenland White-fronted Geese caught at Wexford, 1983/84-1997/98 based on observations and recoveries of neck-collared individuals using the MARK suite of programs (see text and Appendix 1 for details) 12 . Open symbols indicate those seasons when the hunting season was opened at Wexford for a limited shoot. Note the unusually low survival rate of geese marked as goslings in 1988/89 that was not linked to hunting kill in that season. Probability of moving between sites 0.5 0.4 0.3 0.2 0.1 Wexford to Islay Islay to Wexford 0 1980 1985 1990 1995 2000 Figure 8.5. Transition probabilities for Greenland White-fronted Geese moving between Wexford and Islay and vice versa for each year from 1983/84-1997/ 98. There are no significant trends in the movement of individually marked birds over the period based on observations of neck-collared birds 12 . ford to Islay (e.g. Figure 8.5) or elsewhere, that Greenland White-fronted Geese were more likely to emigrate from Wexford in winters following those with an open shooting season. Hence, there is no evidence to suggest that the opening of the season in very recent years has had a demonstrable additive effect on annual adult survival rate or has enhanced emigration rate. 8.5 Conclusions and discussion Ruttledge & Ogilvie (1979) suggested that the loss of peatland habitat might have concentrated Greenland White-fronted Geese into areas where they were easier to shoot. Not only would this have had an adverse effect on survival rates, but it would also have made them more sensitive to hunting disturbance. Human disturbance in general has since been shown to have a major influence on the size and trends in numbers of several flocks (Norriss & Wilson 1988, 1993, MS14). In former times, the bogs and moorlands they exploited would have provided food, daytime resting areas and nighttime roosts all with very little disturbance. It would therefore seem likely that the extensive historical loss of such feeding sites for wintering flocks and increasing levels of disturbance, reduced their ability to acquire necessary stores to survive and reproduce at that time. It does seem likely that habitat loss in such a sitefaithful population made it more vulnerable to hunting and disturbance. Since hunting does appear to have a direct depressing effect on overall survival rate, it seems more likely that increased susceptibility to hunting (prior to the 1980s) caused the declines and extinctions that occurred then. Nevertheless, reduction in breeding output through failure to accumulate sufficient body stores could also have resulted from the increased disturbance experienced at unfamiliar wintering sites. However, we shall never know precisely how changes in habitat availability affected the demography of the population and caused the changes in local wintering numbers at specific sites. There is no doubt, however, that despite continued loss of traditional peatland feeding areas during the latter part of the 20 th Century, the Greenland White-fronted Goose proved itself as able as other grey geese to exploit new and novel agricultural habitats. Flocks initially moved to rough pastures and flooded grassland, but latterly have also exploited intensively managed grass-
lands. This process was certainly underway when the geese began to exploit the newly created Sloblands in Wexford Harbour (probably at or around 1910, Ruttledge & Ogilvie 1979), despite the complete absence of boglands in the vicinity. Despite their traditional habitat and high winter site fidelity, these geese have shown an ability to exploit new habitat opportunities. That said, only one flock of White-fronted Geese is known to have colonised and established an entirely new wintering site since 1982. The process of exploiting grassland habitats, either those that are seminatural or of low intensity agriculture, has continued to the present day. Although many flocks still resort to peatland habitats to feed and sleep at night, there are few flocks remaining that exploit bogs by day (MS14, MS24). Norriss & Wilson (1993) argued that this transition to more agricultural grassland was not forced upon the geese by habitat loss in very recent times, but that the geese responded to the creation of more profitable feeding habitats without loss of traditional ones. This change has been occurring gradually since the 1950s, and therefore does not coincide with the dramatic increase in numbers that has occurred since protection from hunting. Hence, while it is possible to argue that increases in total numbers since the 1970s have been associated with increasing use made by the population of more intensively managed farmland, this cannot be anything more than a contributory factor enabling contemporary increase, rather than the specific cause. This is further supported by the fact that the population range has effectively remained the same in the last 20 years, although several winter flocks have disappeared. This ability to adapt to the exploitation of new habitats may be linked to the availability of such habitats in the neighbourhood of traditional flock ranges. In areas of Scotland where extensive areas of intensively managed grassland are available (e.g. Islay, Kintyre, Stranraer), Greenland White-fronted Geese have switched to these whilst retaining traditional roosts. This process has presumably run in parallel with improving grassland management practices since the early 1960s. In areas with little intensive grassland management and no tillage (e.g. many of the Hebridean islands such as Jura, Mull, Skye and Lewis) flocks remain small (see land use classification maps in Mackey et al. 1998). Equally, in areas with suitable extensive arable and managed grassland but no traditionally used roosts, the species is totally absent (e.g. in Ayrshire and large areas of Dumfries). However, flocks with wintering areas with the greatest area of improved grassland within traditionally used areas have tended to show increases in their number. This is in contrast to those flocks where land use has changed little, or agricultural land has been abandoned. In this way, there appears some fitness consequences to the availability of managed grassland which affects the rate of change in local wintering numbers, although it is far from clear if these relate to annual adult survival, reproduction or rates of immigration/emigration. Investigations of these parameters in relation to habitat and individual quality remain a priority for future research. In contrast, it would appear from the evidence presented here and in MS14 that, prior to protection, the numbers of birds wintering at Wexford and Islay were limited prior to protection by the numbers shot. These two sites have held some 60% of the population since protection, hence this limitation was a significant one. There are no accurate collated hunting statistics for Islay. Since protection on the wintering grounds in 1982, the return rate of birds to Wexford and Islay has been more or less constant. At Wexford, incorporating the numbers killed into a simple model suggests that the return rate has not changed since the late 1960s. Hence the product of annual survival and emigration/immigration balance has remained constant at around 88.4% over 3 decades of largescale land-use change. The relative stable numbers during 1968-1982 seem to have been due to the balance between hunting off-take and changes in annual breeding success. Immediately after protection, numbers increased consistent with the same probability of annual return rate. In the absence of the hunt, this resulted in the increased numbers. The increase has continued at rates regulated by the potential of reproduction to replace lost individuals. Since the start of the 1990s, the numbers wintering at Wexford have shown signs of decline due to falling fecundity (chapter 6) and to catastrophic losses of young and their parents in 1990, hence declines in reproduction appear now to be limiting the numbers at Wexford. Since the reduction in fecundity is mirrored amongst the wintering numbers on Islay and perhaps other wintering areas as well, this seems to be a general phenomenon in the population as whole in recent years. On Islay, the reduction in reproduction rate has 71
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Contents Summary ..................
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Summary The Greenland White-fronted
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Greenland White-fronted Geese are u
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Dansk resumé Den grønlandske blis
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1 Introduction 1.1 Why Greenland Wh
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The Greenland White-fronted Goose i
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more direct measures of 'body condi
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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 and 64: mass at different stages of regrowt
Page 65 and 66: of available fresh green growth of
Page 67 and 68: 8 Survival 8.1 Introduction Almost
Page 69 and 70: the hunting mortality rate K t for
Page 71: during the period when the populati
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.
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The Greenland White-fronted Goose Anser albifrons flavirostris

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