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

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where x = age. The fertility rate is therefore: f= p m~ 1 (2) where p represents the survival rate. The proportion surviving (survivorship) to each age (li) is: X CC.) x=O The intrinsic rate of growth of the population (r) is then calculated iteratively from Lotka’s equation: Before introducing uncertainty in the estimation of birth and survival rates, it is instructive to use a simple example to examine the magnitude of differences expected in demographic statistics. The example is based on Coulson’s (1984) Common Eider data. No estimate is given for juvenile survival rate. Juvenile survival rate is, therefore, initially solved for by assuming r = 0 and solving equation 4. If a population were to grow at the same rate for a long period of time, eventually the proportion ofanimals in each age would remain the same from year to year. This is called stable age distribution. The proportion of first-time nesters (recruits) to the total number of nesters can also be calculated. The proportion first-time nesters can be estimated from banding data (Coulson 1984). This proportion can potentially serve as a diagnostic to tell whether the nesting population is primarily old birds (a sign of low recruitment) or young birds (a sign of lowered adult survival). If we assume that a population decline can be attributed to change in a single parameter, we can calculate the stable age distribution and the proportion ofrecruits. The results of assuming a 15%/year decline (the estimate from the YKD ground plot data; Stehn et al. 1993), are presented in Figure Ill-la. Most of the population is 0-year-olds (eggs) which makes detecting differences in older categories difficult to see. A more informative depiction of age structure includes only ages older than two (Figure llI-lb). If we assume that the current rate of decline is the point estimate from the ground plot survey (r = -0.15), we can ask what proportion of nesting females would be first-time nesters if the decline was solely because of decreases in various parameters. If the decline was due entirely to reduced juvenile (first-year) survival rate, the proportion of first-time nesters is much less (6.3%) than if the decline was due to a reduction in adult survival rates (21 %). Two factors suggest that the age structure may have changed towards a higher proportion Appendix III- Page 2
z o 0.8 a- 0 a- 06 ~0.4 z 0 p0.2 0 a- 00 a- 0 5 10 15 20 25 —u—R=O + REDUCEJUVSURV -+-REDUCEALLSURV - ~.. REDUCE ADLT SURV ~ REDUCE FERTILITY Zoo5 0~ F ~004 a- 0 0. 0.03 U- 0 ~0.02 F o 0.01 0. 0 0.0 0 AGE —m—RuO ~- REDUCEJUVSURV -+-REDUCEALLSURV - ~. REDUCE ADLT SURV -K REDUCE FERTILITY PROPORTION RECRU~5 IN BOXES 5 10 15 20 25 AGE Figure 111-i. Stable age distribution for Common Eiders based on Coulson’s (1984) data. All ages are shown in a. The key below the figure indicates the type of model. The initial model (r = 0) is shown for purposes of comparison. The models for reduced survival (r = -0.15) are: reduction in juvenile (first-year) survival rate, reduction in all survival rates, reduction in adult survival rate, and reduction in fertility. Only ages >2 are shown in b”. The proportion of the total nesting population that is first-time nesters is shown in boxes for the different models. Appendix rn -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
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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
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 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 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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