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

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The final risk factor is the effect of genetic changes, such as loss of heterozygosity and inbreeding depression, upon population fitness (translated as population growth rates). Mating among closely related individuals can expose lethal recessive alleles, which can compromise either survival or fecundity of the individual. Loss of heterozygosity has been linked to reduced fitness and can lead to a reduced ability of the species to adapt to new circumstances. As with demographic stochasticity, inbreeding depression is important only for small population sizes. Not only must these factors be integrated into a single model, but the model must be stochastic in nature. Deterministic models, such as the Leslie model for demographic projections, are inadequate for two reasons. First, deterministic models usually cannot incorporate changes in demographic parameters that are caused by low population size, such as demographic stochasticity and density decompensatory mechanisms (mechanisms that reduce birth and survival rates at low density such as reduced ability to defend against predators, difficulty in finding a mate, etc.). Second, deterministic models have difficulty incorporating variations in birth and survival rates and synergistic effects between risk factors. Synergistic effects are expected in small populations and are referred to as extinction vortices (Gilpin & Soul~ 1986). An example would be a decreased population size that is initially caused by environmental variation that then leads to loss of genetic variability, which further leads to a reduction in population growth rate and a further population decline. Although there are benefits to using more detailed models to model extinction, these stochastic models require the estimation of many parameters and, hence, require many data. For this reason, analytical models that allow the calculation of extinction statistics from data on the population’s mean growth rate and the variance in that rate have been developed. One group of models allows the calculation of expected (mean) extinction time (Leigh 1981; Richter-Dyn and Goel 1972; Goodman 1987). These models solve for the mean extinction time and are analytical models. Unfortunately, because population growth is a multiplicative process, extinction distributions tend to be log-normally distributed. A log-normal distribution of extinction probabilities peaks on the left side and has a long tail on the right. This results in the median probabilities of extinction (the time with a 50% chance ofgoing extinct) that is much less than the mean extinction time. The probability of extinction which corresponds to the mean extinction time (the statistic given by the aforementioned analytical models) is unknown. The mean actually corresponds to the balance point in the lop-sided log-normal distribution: a point of questionable relevance to managers. Managers are usually interested in low probabilities of extinction, such as a 5% or 20% chance of going extinct. Another analytical model that avoids the need for detailed demographic data and yet gives an analytical means of calculating an entire extinction distribution from a time series of abundances was developed by Dennis et al. (1991). The accuracy of this technique depends on two critical assumptions: (1) abundance estimates are for the entire population; and (2) abundance estimates are very accurate, so that interannual variance reflects actual population fluctuations and not imprecision of abundance estimates. Unfortunately, as populations Appendix I - Page 2
decrease, so does the precision of estimating abundance (Taylor and Gerrodette 1993). The result is that for most endangered or threatened populations (including the Spectacled Eider) this analytical technique cannot be used. The common solution for uncertainty in parameter estimation in PVA models is to model a series of possible scenarios that use a different set of parameters. Each scenario yields a distribution of extinction times. Each distribution will give a different MVP, each of which could be possible. It then becomes a management problem to decide which is the most prudent value for MYP. The strategy followed in this PVA is to incorporate the uncertainty in parameter estimation into a single extinction probability distribution. Instead of modeling extreme values for each unknown parameter, parameters are given a probability distribution between minimum and maximum values, and these distributions ofpossible values determine the distribution of population responses. Thus, the distribution reflects two types of uncertainty: (1) uncertainty because of the stochastic nature of population dynamics; and (2) uncertainty because of our ignorance about the population dynamics as reflected in the uncertainty in estimating parameters used in the model. Background on Spectacled Eiders Details on the biology of Spectacled Eiders are presented in the introduction to this recovery plan. The object of this section is to highlight points relevant to the PVA. Because population sizes are still much larger than those in which inbreeding becomes a problem, genetic factors are unlikely to contribute to a diminished growth rate. Further, the effect of inbreeding or loss of heterozygosity on sea ducks is unknown. Therefore, a genetic component will be omitted from the PVA with the knowledge that extinction times will possibly be biased positively (i.e., toward longer times) because of this omission. This plan divides the species into three geographically defined populations. Even if these populations do not prove to be genetically distinct, this division is wise as a tactic for reducing extinction risk. It is a general tenet of conservation biology that more than one population should be maintained; single populations are susceptible to local catastrophes such as severe weather and oil or chemical spills. Spectacled Eiders are perhaps more susceptible to loss of populations than many species because: (1) they are an arctic species and may have naturally variable population sizes because of large interannual variations in weather and resources; (2) the distribution of this species is highly concentrated at times; and (3) this species probably has a low recolonization rate. Female eiders are known for having high site fidelity (Cooch 1965; Wakely 1973; Milne 1974; Dau 1974; Reed 1975; Swennen 1976; Wakely and Mendall 1976). Scientists have argued that areas that have been locally depleted may take many years to be recolonized, if indeed recolonization occurs at all (Cooch 1986). In addition, the distribution of Spectacled Eiders at sea can be very clumped (W. Lamed, pers. comm.). Appendix I - Page 3
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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
Page 8 and 9:
TABLE OF CONTENTS DISCLAIMER PAGE 1
Page 10 and 11:
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
Page 62 and 63: . 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 114 and 115: This PVA will treat two population
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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