A. Status of the Spectacled Eider - U.S. Fish and Wildlife Service

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This PVA will treat two population types: (1) the Yukon-Kuskokwim Delta (YKD) population (for which good information on population trends is available); and (2) an “unknown” population, which describes the North Slope (NS) population and the Arctic Russian (AR) population. The YKD population type will provide specific estimates of extinction probabilities, whereas the “unknown” type will provide guidance for choosing criteria for classification decisions. Finally, estimates ofMVP sizes and expected time to go from various population sizes to a critical size (i.e., 125 pairs) are made to provide additional quantitative guidance for selecting criteria used for classification decisions. M~LbQd~ The preferred method for conducting an accurate PVA is to develop a demographic model that includes information on age-specific birth and survival rates, the way in which those rates vary through time, and the way in which those rates change with population density. Not only are these data unavailable for Spectacled Eiders, but crucial elements are missing from detailed studies of Common Eiders (Mime 1974, Swennen 1983, Coulson 1984) which might otherwise serve as an adequate surrogate for modelling purposes. Perhaps the most important missing data are estimates of first-year survival rates and the variability in those rates. It is theoretically possible to calculate those rates given information on adult survival rates, birth rates, and rates of survival to fledging. Unfortunately, using the estimates provided in published accounts of the Common Eider, studies to derive juvenile survival rate often resulted in nonsensical values, such as survival with a probability > 1. For this reason, a detailed demographic model for the PVA was not possible (although a separate Appendix (III) on eider demography is included). Instead, a simple model of exponential growth was used. This model uses a mean growth rate and a variance in growth rate to project population sizes through time. Variance in growth rate for Spectacled Eiders is unknown. Figure I-i shows the influence of variability in population growth rate on the distributions of extinction times. The example considers the case where the average growth rate is a 5%/year decline (r = -0.05) and the initial population size is 5,000 pairs. Three curves are shown for increasing variability in population growth rate (small--coefficient of variation (CV) = 0.05; medium--CV = 0.15; and large--CV = 0.25). Clearly, the more variable the growth rate of a population, the higher are its chances of experiencing a string of years of bad luck that could• lead to extinction. Indeed, high variability in population growth rates has been correlated with increased probabilities of population extinction in wild populations of lagomorphs (Souls 1987). There are two studies on Common Eider~s from which estimates of population growth variability can be made. In Scotland, wintering eiders can be counted with high accuracy (Milne 1974). A 10-year time series ofpopulation estimates (which included a year of high adult mortality from an oil spill) yielded a standard deviation (s) for r of 0.21. At about the same time, a nesting population in the Netherlands had an s = 0.07 (Swennen 1983). For the Appendix I - Page 4
PVA we chose randomly from a uniform distribution of variability in growth rates, between 0.07 and 0.21. I ~O.8 ~0.6 0. w ~0.4 I- -J 0.2 C.) 0 Figure I-i. Cumulative probability of extinction for populations initially numbering 5,000 pairs, with a mean (geometric) growth rate of -0.05. The figure shows that not only does the median time to extinction decrease as growth rate becomes more variable, but that the variance in extinction tame increases. Yukon-Kuskokwim Delta PVA CV= 0.15 CV = 0.05 CV = 0.25 —*‘. 0 50 100 150 200 YEARS A dramatic decline has been documented for Spectacled Eiders on the YKD (Stehn et al. 1993) (see Figure 2 in the Introduction). Time series from three surveys were available: the North American Breeding Pair Survey (YKD segments), the random ground plot survey, and the aerial survey of coastal YKD. For clarity these will be referred to as the breeding pair survey (an aerial survey), the ground plot survey and the coastal aerial survey. These data on trends should provide the basis for • estimating the population growth rate and the uncertainty in that rate. The population growth rate is the primary parameter determining the probability of extinction. Statistically-based abundance estimates can be used in classical Bayesian analyses to yield a probability distribution for population growth rates. The estimates ofabsolute abundance with associated estimates of precision are used to calculate the statistical likelihood of hypotheses ofpopulation growth rate. Appendix I - Page 5 4
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SPECTACLED EIDER RECOVERY PLAN Team
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LITERATURE CITATION U.S. Fish and W
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EXECUTIVE SUMMARY OF THE RECOVERY P
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TABLE OF CONTENTS DISCLAIMER PAGE 1
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LIST OF FIGURES Figure 1. Breeding
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A. Status of the Spectacled Eider R
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) a) j~ 25000 0 2 220000 C ~15000 ~
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B. Causes for Decline and Obstacles
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Increasing interest in avicultural
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Other conservation measures include
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D. Natural History of the Spectacle
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Figure 4. Yukon-Kuskokwim Delta loc
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DEL?A RUSSIA SPECTACLED EIDER RANGE
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helicopter surveys in the Prudhoe B
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geographic populations, because imm
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Figure 8. Study sites and land stat
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their diseases (e.g., Schiller 1954
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E. Distinct Population Segments The
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A final consideration involves info
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Trend data are analyzed to inform w
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Figure 10. A hypothetical posterior
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thresholds are not “magic numbers
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Criteria for Reclassifying from Thr
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Criteria for Delisting from Threate
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The final aspect ofSpectacled Eider
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concordance in their descriptions o
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data on both levels and effects oft
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implicated. In the absence of histo
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. - currently small size of the YKD
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implementation of the Memoranda ofA
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. take of Spectacled Eiders. In add
Page 64 and 65: . AlS. Produce a handbook summarizi
Page 66 and 67: . Bl.4. 1.3. Develop visibility cor
Page 68 and 69: B2. 1.1. Implement YKD satellite tr
Page 70 and 71: . Appendix Ill). Since epidermal ag
Page 72 and 73: . feasible if post-fledging staging
Page 74 and 75: presumed that their activities have
Page 76 and 77: contaminants within Spectacled Eide
Page 78 and 79: limited ability to withstand additi
Page 80 and 81: surface after a year and is no long
Page 82 and 83: . The reproductive stages (eggs, yo
Page 84 and 85: is inadequate to sustain “normal
Page 86 and 87: ___________ 1967. The geese of the
Page 88 and 89: Dementev, G.P., and N.A. Gladkov (e
Page 90 and 91: ___________ 1 964a. Observations on
Page 92 and 93: Nelson, E.W: 1887. Report upon natu
Page 94 and 95: ________ P.R. Wade, R.A. Stehn, and
Page 96 and 97: Robert M. Platte, Migratory Bird Ma
Page 98 and 99: KEY Task Duration and Costs TBD - T
Page 100 and 101: TASK 324.2 I 12.4.1 .2 PRIOR- — 2
Page 102 and 103: TASK I — [37 E12 EI.3 fTYU —PRI
Page 104 and 105: TASK PRIOR- Dj ITYU — — A12.3 2
Page 106 and 107: — TASK U — 135.2 PRIOR- TASK DE
Page 108 and 109: TASK U PRIOR- ITY U TASK DESCRIPTIO
Page 110 and 111: TASK PRIOR. U — DS.3 3 TASK DESCR
Page 112 and 113: The final risk factor is the effect
Page 116 and 117: Both aerial surveys are conducted a
Page 118 and 119: 0.2 0.15 -j i 4 0.1 0 -I 0.05 0.08
Page 120 and 121: emaining before the population reac
Page 122 and 123: ) critical population size; and (2)
Page 124 and 125: 40%. The population growth rate cri
Page 126 and 127: Table 1-2. Results of simulation wh
Page 128 and 129: Hilborn, R. and C.J. Walters. 1992.
Page 130 and 131: APPENDIX II TECHNICAL DETAILS OF TH
Page 132 and 133: The likelihood function for the par
Page 134 and 135: initial sample. Then the O~ were re
Page 136 and 137: LU ~0.8 z -J ~0.6 I-ET1 w107 480 m1
Page 138 and 139: LITERATURE CITED APPENDIX LI De la
Page 140 and 141: where x = age. The fertility rate i
Page 142 and 143: of older females: (1) older females
Page 144 and 145: RESULTS Solutions for single cause
Page 146 and 147: 0.1 0.08 ~0.06 4 0 0.04 0. 0.02 0 0
Page 148 and 149: growth rate. Perhaps this can be mo
Page 150 and 151: decline, by far the fastest way to
Page 152 and 153: LITERATURE CITED APPENDIX In Bailli
Page 154 and 155: APPENDIX IV SPECTACLED EIDER RECOVE
Page 156 and 157: APPENDIX V COMMENTS RECEIVED ON DRA
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A. Status of the Spectacled Eider - U.S. Fish and Wildlife Service

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