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

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thresholds are not “magic numbers” that guarantee extinction or recovery. Instead, these thresholds serve as mileposts that identify populations at high risk and measure progress at reducing that risk. For example, the World Conservation Union (International Union for the Conservation of Nature [IUGNI)has suggested risk levels (i.e., thresholds) for classifying species (see Appendix I). The Service considered the IUCN criteria as guidelines in developing the reclassification criteria for Spectacled Eiders. Specificafly, the IUCN has identified a population level of 125 pairs as critically endangered, and the population models in Appendix I of this plan use 125 pairs as a benchmark for assessing the risk of extinction. There is no particular biological significance to the exact number chosen for the “critical” population size. The value could just have easily been 150 or 100. Despite the somewhat arbitrary nature of the number, however, such a figure has both heuristic and practical applications. Consider a population of 2,000 pairs (roughly the size ofthe Spectacled Eider population on the YKD in 1994). If the population declines at a rate of 5%/year, extinction is over a century away, but the population will spend nearly half of the next 100 years at numbers less than 125 pairs (Figure 11). Thus, the extinction time gives an overly optimistic picture of how much time remains for conservation action to be implemented effectively. In other words, in most cases, once a population falls below abQut 125 pairs, only the most radical conservation efforts will result in its full recovery. The critical population size, therefore, is used as a practical baseline to estimate the time remaining for constructive research and recovery actions. The reclassification criteria presented below should be viewed in the same light. Passing a specific population threshold defined in this plan neither seals the fate ofdeclining populations nor secures the future for increasing populations. Rather than defining biological failsafe points, the criteria identify thresholds at which the Service’s level ofconcern about a population changes. The calculations in the appendices provide a quantitative framework of objectivity for what are, ultimately, subjective decisions. By indicating when different levels of protection are required, the criteria represent the Service’s most prudent assessment of a population’s risk. 34
(I) 0 IL 0 Co 0~ 2000 1750 1500 1250 1000 750 500 250 0 1 POPULATION Critical level TRAJECTORY WITH A 5%/YEAR DECUNE 0 10 20 30 40 50 YEARS 60 70 80 90 100 Figure 11. A population of 2,000 pairs, declining at 5%/year. will reach the IUCN critical level of 125 pairs in just 55 years. Although extinction does not occur within the first 100 years, 94% of the population has been lost by the time it reaches the critical level. (Figure by D.Burn) 35
Page 2 and 3: SPECTACLED EIDER RECOVERY PLAN Team
Page 4 and 5: LITERATURE CITATION U.S. Fish and W
Page 6 and 7: 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
Page 12 and 13: A. Status of the Spectacled Eider R
Page 14 and 15: ) a) j~ 25000 0 2 220000 C ~15000 ~
Page 16 and 17: B. Causes for Decline and Obstacles
Page 18 and 19: Increasing interest in avicultural
Page 20 and 21: Other conservation measures include
Page 22 and 23: D. Natural History of the Spectacle
Page 24 and 25: Figure 4. Yukon-Kuskokwim Delta loc
Page 26 and 27: DEL?A RUSSIA SPECTACLED EIDER RANGE
Page 28 and 29: helicopter surveys in the Prudhoe B
Page 30 and 31: geographic populations, because imm
Page 32 and 33: Figure 8. Study sites and land stat
Page 34 and 35: their diseases (e.g., Schiller 1954
Page 36 and 37: E. Distinct Population Segments The
Page 38 and 39: A final consideration involves info
Page 40 and 41: Trend data are analyzed to inform w
Page 42 and 43: Figure 10. A hypothetical posterior
Page 46 and 47: Criteria for Reclassifying from Thr
Page 48 and 49: Criteria for Delisting from Threate
Page 50 and 51: The final aspect ofSpectacled Eider
Page 52 and 53: concordance in their descriptions o
Page 54 and 55: data on both levels and effects oft
Page 56 and 57: implicated. In the absence of histo
Page 58 and 59: . - currently small size of the YKD
Page 60 and 61: 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
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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
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TASK 324.2 I 12.4.1 .2 PRIOR- — 2
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TASK I — [37 E12 EI.3 fTYU —PRI
Page 104 and 105:
TASK PRIOR- Dj ITYU — — A12.3 2
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— 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
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0.2 0.15 -j i 4 0.1 0 -I 0.05 0.08
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emaining before the population reac
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) critical population size; and (2)
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40%. The population growth rate cri
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Table 1-2. Results of simulation wh
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Hilborn, R. and C.J. Walters. 1992.
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APPENDIX II TECHNICAL DETAILS OF TH
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The likelihood function for the par
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initial sample. Then the O~ were re
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LU ~0.8 z -J ~0.6 I-ET1 w107 480 m1
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LITERATURE CITED APPENDIX LI De la
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where x = age. The fertility rate i
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of older females: (1) older females
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RESULTS Solutions for single cause
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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
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decline, by far the fastest way to
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LITERATURE CITED APPENDIX In Bailli
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APPENDIX IV SPECTACLED EIDER RECOVE
Page 156 and 157:
APPENDIX V COMMENTS RECEIVED ON DRA
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