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

More documents

Recommendations

Info

emaining before the population reaches critically low levels. The choice of 125 pairs stems from the classification criteria proposed for use by the World Conservation Union (IUCN) for the category “critical” (Mace and Stuart 1994). Biologists are aware that, when populations reach very low levels, population parameters are likely to change. For example, birth rates may change because of difficulty in finding mates or for colonial species survival rates may decline because of difficulties in defending territories against predators. If the cause ofthe population decline is unknown (the case for Spectacled Eiders), time will be required to find the cause(s) of the decline. The most productive research will occur with population sizes higher than this critical level. Similarly, the range of useful management actions is greatly reduced at very small population sizes. By the time a population reaches 125 pairs the most serious management option is taking the remaining birds into a captive breeding program. This is a particularly undesirable outcome if the cause of the decline is still unknown. It is therefore useful to know how much time is available before critical levels are reached. The results of the simulations are shown in Figure 1-4. Criteria for classification as endangered are usually defined in terms of either probabilities of extinction or population growth rates. Various criteria have been proposed for classification as endangered (Shaffer 1981; Mace and Lande 1991; Mace et al. 1992). The Mace and Lande (1991) criteria IUCN wI- I— 0.9 0) ~ 0.8 - z 00.7- Cntical — — 9~ ‘U ~ 0.6 I- 2 w 0.5 0 w 0.4 a- ~ 0.3 - 0.2 ‘Extinct ~0.1 U 0 o 25 50 75 100 125 150 175 200 225 250 275 300 325 350 375 400 TIME (YEARS) FROM 1995 Figure 1-4. Cumulative probability curves for the time to reach critical (125 pairs) and the time to extinction. Appendix I - Page 10
scheme (Mace and Stuart 1994) allow use of either growth rates or extinction probabilities but they are not necessarily consistent. We know that for the same mean rate of decline, probabilities of extinction will increase as variance in population growth rate increases. Because the criteria use only one estimate for population growth rate, it will only match to the probability of extinction for a single variance. According to the rate of decline criteria (the IUCN criteria are also at r =-0.05 for the Endangered category), Spectacled Eiders on the YKD would qualify as Endangered under any of the aforementioned criteria. In contrast, the YKD population does not qualify as Endangered since it does not reach a 20% chance of extinction in 38 years or 5.2 generations, given the mean generation time (Fig. 1-3). Under the current IUCN criteria, Spectacled Eiders would qualify for the less risky. Vulnerable category using the extinction probability criteria. Note that an earlier draft of the IUCN criteria used a 20% chance of extinction in 10 generations and that the YKD population would qualify under these less stringent criteria. Endangered classification would be warranted under the recovery objective for endangered in this plan and we further discuss why in Appendix II, which covers decision analysis. The Unknown Population This section strives to give guidance on setting appropriate criteria for classifying populations into the different risk categories (i.e., endangered, threatened, delisted). The category of endangered is examined first. As shown in Figure I-i, probability of extinction is a function of both population growth rate and the variance in that rate. For population growth rates ranging from -0.01 to -0.16 and population sizes ranging from 1,000 to 5,000 pairs, simulations were conducted as follows: (1) choose variation in growth rate from a uniform distribution ranging from standard deviation (s) = 0.07 to 0.21; (2) project population for 1,000 years. [Notethat s is used rather than CV because as the mean growth rate (r) goes to zero, the CV goes to infinity.] The median probability of reaching critical population size was recorded for each of 10,000 simulations (Figure 1-5). At high rates of decline, increasing population size has little effect on the time to reach critical. For example, assuming r = -0.15 (the estimated rate from the ground plot surveys) it would take
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 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
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 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 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
show all

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

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?