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

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data on both levels and effects ofthis contamination, efforts to assess contamination should be strongly encouraged. e. EQQdllabijs--The habitats used and prey items selected by foraging Spectacled Eiders away from the breeding grounds remain largely unknown. This absence of data prevents an evaluation of hypotheses attributing the decline in eiders to either natural or anthropogenic changes in the trophic structure of Bering Sea food webs. Similarly, without knowing where and what eiders eat, researchers will be unable to determine the pathways by which birds might accumulate contaminants. f. Han~sLLcy.els--Even if available data do not indicate that human harvest triggered or contributed markedly to the decline ofSpectacled Eiders, harvest is still an obstacle to recovery. Despite the small absolute numbers reported in recent harvest surveys, a low but constant harvest level will have an increasing impact as population size declines. Of all known sources of mortality, however, the human harvest of Spectacled Eiders is potentially the most manageable. Increasing adult survival is probably the most effective means to improve population growth (see Appendix III). To assess both the contribution of harvest to population trends and the efficacy of specific management actions, a statistically robust estimate of harvest is necessary. In theory, the magnitude of mortality by intentional and incidental harvest can be estimated more rigorously and can be reduced more rapidly than can any other source of mortality. It will be necessary to evaluate, refine, and expand current harvest monitoring efforts to include all geographic areas and seasons in which harvest occurs. As with population monitoring, the power of both ongoing and developing harvest surveys needs to be determined. Current survey design was not intended and is inadequate for documenting either annual variation or trends in harvest levels. For example, although the current harvest survey on the YKD is statistically valid, it is not powerful: the annual 95% CI for 1985-1992 averages ±80%ofthe harvest estimate. In other words, the survey is insensitive to all but extreme changes in harvest levels. Greater precision could be achieved by restratifying and restricting the analysis to those communities known to harvest Spectacled Eiders or by increasing the sample size. All avenues of survey improvement should be explored promptly, for both managers and modelers will require estimates of harvest that are as accurate and precise as possible. g. Er~d~ljnn--On the breeding grounds, eggs, ducklings, and (to a lesser extent) adults are susceptible to predation. Foxes, jaegers, and large gulls are probably the most serious threats during nesting and brood-rearing. Because detailed studies of the Spectacled Eider were not initiated until the population decline was already underway, it is not known if predation rates in the last few decades have been higher than historical levels. Several lines of evidence suggest that predation rates have increased, perhaps as a result of declines in the abundance ofalternative prey resources or ofputative increases in predator numbers. 44
Whether such changes in predator-prey relationships can account for the eiders’ decline has not been determined. Like human harvest, predation is a known source of Spectacled Eider mortality and may prove amenable to active management efforts at a local level. The effectiveness of fox control as a management tool for enhancing eider production needs to be evaluated more thoroughly. Similarly, the efficacy and limitations of gull control for improving eider production need to be assessed. h. n~jg~s--In Section ll.A, several reasons are provided for managing and assessing the status of Spectacled Eiders at the population level. Although studies of nuclear DNA indicate a single panmictic population of spectacled eiders (K. Scribner, pers. comm.), it has not yet been determined whether these populations can be identified by distinctive mitochondrial DNA markers or if they differ in behavioral or ecological characteristics that reflect heritable differences. If there are consistent genetic differences among breeding areas, the need to maintain genetic diversity in the species will provide additional impetus for management at the population level. The degree of population-level distinctiveness also may affect efforts to define viable population sizes for future recovery planning. Finally, using genetic markers to link eiders sampled during the non-breeding season to specific breeding populations with differing growth rates may provide a context for evaluating hypotheses concerning the cause(s) of the decline and obstacles to recovery. Therefore, it is important to determine the genetic profile and identify potentially heritable traits of birds breeding in each of the three major populations. i. Diseases and Parasites--Few data have been collected on the impacts of diseases and parasites on Spectacled Eiders. Both factors, however, are known to contribute to mortality in the more-thoroughly-studied Common Eider. Although these phenomena are a natural aspect of waterfowl ecology, other debilitating factors (e.g., food limitation, contaminant loads) may be acting synergistically to increase the susceptibility of Spectacled Eiders to disease and parasites. Physiological Condition--Waterfowl frequently exhibit significant intrapopulational variation in body condition (e.g., fat level, body mass). Recent investigations support the hypotheses that mortality is high or productivity is low among individuals with poor body condition (Esler and Grand 1994). An analysis of the body condition of Spectacled Eiders might indicate which group of mortality factors is contributing significantly to the decline and/or preventing recovery. Specific physiological or histopathological markers also can serve as indicators of specific disease or stress conditions, including environmental contaminants. Poor body condition could be a symptom of heavy metal contamination, food scarcity, parasites, or disease. If the distribution of Spectacled Eider body conditions differs from related species that are sharing similar habitats, these mortality factors might be implicated. If the distribution of body conditions is comparable to that for other similar species, however, other mortality factors (e.g., predation, subsistence harvest) would be 45
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 44 and 45: thresholds are not “magic numbers
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 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
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
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— TASK U — 135.2 PRIOR- TASK DE
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TASK U PRIOR- ITY U TASK DESCRIPTIO
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TASK PRIOR. U — DS.3 3 TASK DESCR
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The final risk factor is the effect
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This PVA will treat two population
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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
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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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A. Status of the Spectacled Eider - U.S. Fish and Wildlife Service

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