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

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of older females: (1) older females in Common Eiders have larger mean clutch sizes (Baille and Mime 1982); and (2) mean clutch size has increased significantly on the YKD (Stehn et al. 1993). Although this increase in clutch size could be a density dependent response to reduced population size (Hario and Selin 1988), we would be encouraged to gather evidence on the proportion of new nesters if we had survival data of the quality of Coulson‘s. Of course, we do not currently have sufficient data on Spectacled Eiders to estimate survival rates. It is therefore reasonable to ask whether, given the range of survival rates for Common Eiders, we expect to see differences in values (e.g., the proportion of first-time nesters), that would allow hypothesis testing with a high probability of correctly detecting a difference. The approach taken is similar to the exercise presented above. Parameter values for the first four parameters listed above are chosen from plausible distributions for those values based on Common Eider data where the population growth rate was thought to be near stable (r = 0). Because the null hypothesis is that the population is stable (r = 0), the final parameter, firstyear survival rate, is solved to yield this growth rate. The alternate hypothesis is that one of the parameters decreased to give a plausible rate of decline for the YKD (chosen from the post-model distribution for the ground plot surveys in Appendix I). By decreasing adult survival, first-year survival and fertility separately, we can calculate distributions of what values these parameters would need to be to have been the sole cause of the decline. Comparison of these distributions then helps us assess whether demographic research will be likely to be able to eliminate hypotheses concerning the proximate cause of decline. For example, if we knew thatjuvenile survival was the primary cause of the decline, research priorities would be shifted to finding the cause for the reduction in juvenile survival. To incorporate uncertainty in the four demographic parameters, each is drawn randomly from distributions intended to cover the possible range of values for that parameter when r = 0. For Common Eiders, demographic parameters each have quite large ranges. Because our understanding of how these parameters might represent Spectacled Eiders is rudimentary, we chose to represent most probability distributions with a triangular distribution. The triangular distributions are defined by the minimum and maximum values for the parameter found in the literature and have a maximum probability at the mean between the extreme values. Estimates of mean clutch size from Spectacled Eiders in Alaska are used for the premodel distribution (minimum = 4.05, maximum = 5.92, maximum probability of triangular distribution = [minimum+ maximum]/2 = 4.985). This minimum is the 1965-1976 mean (4.688) less 2 standard deviations (0.3176). The maximum is the 1986-1992 mean (5.104) plus 2 standard deviations (0.406) (Stehn et al. 1993). Data for the proportion of adult females nesting are: mean = 0.753 (Milne 1974), mean = 0.78 (Coulson 1984), 0.78-0.90 (Baillie and Milne 1982). Based on these values we used a triangular distribution: minimum = 0.5; maximum = 1.0; maximum probability = 0.75. Estimates of age-specific proportion mature are scarce but support a gradual onset of maturity between the ages of two and five (Reed 1983; Baille and Milne 1982). Estimates from Common Eider populations that do not show evidence of a decline (some were increasing at low rates usually
for the pre-model distribution ofadult survival (minimum = 0.75; maximum = 0.95 based on Table rn-i; maximum probability = 0.85) (Table 111-2). Juvenile survival was calculated as that value that given the other parameter values chosen would yield a population with no growth (r = 0, equation 4). Table rn-i. Adult survival rates for Common Eider novulations not noted as declininf. ADULT SURVIVAL RATE I SOURCE LOCATIONI 0.93-0.96 BAILLE AND MILNE 1982 SCOTLAND > 0.9 SWENNEN 1972 NETHERLANDS 0.75-1.00, COULSON 1984 mean = 0.895 0.85 (AVERAGE OF REED AND ERSKINE VARIOUS STUDIES) 1986 GREAT BRITAIN CANADA 0.83 HARIO AND SELIN 1988 FINLAND 0.826 + 0.099 REED 1983 CANADA 0.77 OR 0.81 WAKELY AND MENDALL 1976 MAINE 0.76, 0.78 WAKELY 1973 MAINE Table 111-2. Parameter ranges used in demographic analysis. PARAMETER MINIMUM MAXIMUM ADULT SURVIVAL 0.75 0.95 CLUTCH SIZE 4.05 5.92 PROPORTION NESTING 0.753 1.000 MAXIMUM AGE 3.5 IMMATURE Appendix rn -Page S 5.0
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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
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 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 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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