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

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growth rate. Perhaps this can be more intuitively understood with a human example. The average age of parents in Sweden, a population which is declining slightly, is much older than the average age of parents in Mexico, a population growing at a rapid rate. The distribution of generation times (using equation 5) for the declining YKD population (Figure 111-7) averages 7.61 (s = 1.68). Generation time is often used as a unit of time in calculating probability of extinction (Appendix I). .1 L’ er 2 1=0 .z—1 ~ 1 rIp .2 I—i ~ e -ri if rip 1=0 .20 .2 Another way to view the broad combinations of demographic parameters possible given our current knowledge is by looking at a scatter plot of estimates of the parameters against growth rate (Figure 111-8). We expect an increase in survival and/or birth rates with increasing growth rates. We observed that although expectations are met, there is a large scatter of possible values for any given growth rate. The large scatter in the range of clutch size as well as the greater amount of increase as growth rate increases is further evidence that this parameter has less of an effect on growth rates than do the other parameters. ~06 4 ~O.4 Figure 111-8. Survival rates and mean clutch size plotted against the resulting growth rate (r). Symbols for the parameters are: adult survival--open square, clutch size--triangle, first-year survival--filled square. (5) 1 4 0.8 3w N V ~, V V V ~ V V V ~ V V CLUTCH SIZE 0.2 V JUVENILE SURVIVAL 10 V • ~ m sm..~2’I’~-~j’ ~ — — 0 —— 0 -0.2 -0 15 -o i -0.05 POPULATION GROWTH RATE (r) Appendix m - Page 10 I-. -J
How do the large number of demographic possibilities affect our ability to test hypotheses about the cause(s) of the decline? As mentioned, the proportion of new nesters could be used to determine whether adult survival or lack of recruitment was the primary cause ofdecline. Incorporating the uncertainty in parameters reduces our ability to detect differences between these alternatives (Figure 111-9). Clearly, if the proportion new nesters/total nesters is greater than 0.22, then reduced adult survival is likely whereas if this proportion is less than 0.12, then reduced recruitment (either reduced fertility or reduced first-year survival) is the likely cause. Although there is some overlap between the distribution for reduction in adult survival and the distributions for reduced recruitment, it is anticipated that actual estimates from Spectacled Eiders will reduce the range for demographic parameters and tighten these distributions. Thus, it is still possible that the proportion of first-time nesters could be a useful diagnostic statistic. Ci~ 0.4 ‘U 1— 0.35 (0 ‘U z 0.3 -J ~0. 25 0 ~0.2 (0 ~0. 15 I- 0.1 ~0. 05 ‘U z 0 PERCENTILES OF 95% THE DISTRIBUTION 50% Figure ~-9. The proportion of nesters which are first-time nesters, assuming the decline was caused by a reduction in: first-year survival only, adult survival only, and fertility only. The squares represent the following percentiles of the distributions: 5%, 50%, 95%. The percentiles are the same for first-year survival and fertility because both have the same effect on recmitment into the breeding population. 5% FIRST-YEAR SURVIVAL ADULT SURVIVAL FERTILiTY PARAMETERS OF CHANGE Despite large uncertainty in demographic parameters, the basic life history strategy of eiders is still quite clear (Figure 111-10). Population growth is most sensitive to changes in adult survival, followed distantly by fertility and juvenile survival. Regardless of the cause of the Appendix m - Page 11
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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
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. AlS. Produce a handbook summarizi
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. Bl.4. 1.3. Develop visibility cor
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B2. 1.1. Implement YKD satellite tr
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. Appendix Ill). Since epidermal ag
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. feasible if post-fledging staging
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presumed that their activities have
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contaminants within Spectacled Eide
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limited ability to withstand additi
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surface after a year and is no long
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. The reproductive stages (eggs, yo
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is inadequate to sustain “normal
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___________ 1967. The geese of the
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Dementev, G.P., and N.A. Gladkov (e
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___________ 1 964a. Observations on
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Nelson, E.W: 1887. Report upon natu
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________ P.R. Wade, R.A. Stehn, and
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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 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 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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