Population Size and Produccion of Geese Nesting on che Yukon-Kuskokwim Delea, Alaska

Field Report: 1 July, 1991

Robert Scehn Alaska Fish and Wildlife Research Cancer, Anchorage, AK 99503

.:like Wege and George Walters Yukon Delea National Wildlife Refuge, Bechel, AK 99599

Introduction:

Annual assessment of production and status of nesting populations of geese on the Yukon-Kuskokwim (YI<) delta was continued this year co provide information for managers, participants in cooperative goose management programs, and the Pacific Flyway technical committees. A ground-based sampling procedure has been used since 1986 to estimate the numbers of total nests, active nests, and eggs for three species of geese, the Cackling Canada goose (Branca canadensis minima), the Emperor goose (Chen canagica), and the Greater White-fronted goose (Anser albifrons froncinalis). Because the sampling also collects useful data on the Spectacled eider (Somateria fischeri), results on this species have been included as well. Annual information on production of young and size of che nesting population will contribuce co the long term data needed to understand goose and eider population ecology and to better manage chese species

.:tethods

The ground based sampling used a stratified design developed for an aerial survey flown since 1985 by W.I.Butler, Jr., Migratory Bird �anagement, USFWS, Anchorage. The aerial survey records single, pair, and flock observations along transects providing an index to total goose populations over the 12,600 km2 of the coastal YI< delta. Boundaries for :6 sampling strata (Fig. 1) were determined based on a combination of physiographic regions and analysis of 1985 survey data. Landsat images a� 1:250,000 scale were used to delineate strata based on similarity of features including lake size and prevalence of ponds, sec�e meadow, and upland tundra. Eight of these strata (Fig. 1) totalin� �663 km2 were sampled by ground plots in 1991 in the coastal region o� Yukon Delta �rational Wildlife Refuge. Sampling excluded the Centr�l Upland strata �i:h 1709 km2 that has been sampled in previous years. Instead, we sampled 399 km2 of coastal South Nelson Island and the adjacent coast south towards Chefornak. Aerial survey data indicates that goose and eider density is higher in chis strata than the General Upland. South Nelson had not been sampled by ground plots since 1987.

Sample plots are randomly located by selecting a random pair of longitude and latitude coordinates for the plot center point. New random locations are selected each year. The order of selection becomes the order of priority for plots to be searched within each stratwn. Rectangular plots around each center point are drawn 809 m (0.5 mi) long and 404 m (0.25 mi) wide oriented in an ease-west direction. The random selection of points and the drawing of plot boundaries is accomplished by a computer programs. Plots are drawn by computer at 1:63,360 scale directly on topographic maps. Even if most or all of a plot is within a river or a large lake it is still included in the sample. Plot boundaries are transferred to color xerox copies of colored infrared aerial photographs (1:15,000) which are available for most plots. These provide field maps co aid in finding plots, searching, and determining exact plot boundaries.

Access to plots is either by Cessna 185 aircraft on floats or by boat. Nearly all plots are within 1.5 miles of a lake or river suitable for landing aircraft. Each plot is searched on a single visit. Nest searching usually takes between 1.5 and 5 hours for two people depending on the complexity of the habitat and the nwnber of nests found. All possible sites dry enough for a nest, particularly lake shores and islands, are examined for all active and destroyed goose, brant. eider, swan, crane, loon, and gull nests. Nests of other species are recorded as encountered but most shorebird, passerine, and duck nests are missed.

A nest card is filled out for each nest to record species, location, number of eggs, evidence of predation, and other pertinent data. A few eggs in many clutches are floated to determine approximate stage of incubation. Even if the adult birds are not observed at the nest, nearly all nests can be identified to species based on down or contour feathers in the nest bowl. Some eider and loon nests are not identified to species and unknowns are included as Spectacled eider or Pacific loon which are more common than Common eider or Red+throated loon. Nest cards are tabulated at the refuge field camp using dBase III+ on a laptop computer. The data are checked, sorted, copied into standard format, tabulated and analyzed by computer programs in the field.

The total number of viable eggs for each species at mid to late incubation is the parameter to be estimated as it most directly relates to production of young. The mean number of eggs per plot, based on the simple random sample of plots within each stratum, is weighted by stratwn area and combined to obtain the overall mean density and population totals. The total number of nests indicates effective breeding pair population size. The number of active nests divided by total nests determines the proportion of nests remaining active, an index to weighted average I nesting success. The number of eggs per active nest (effective clutch size) and average predicted date of hatch is based on all active nests found on random plots. These averages consider each nest as an independent sample unit: averages are not weighted by stratum area, nor is cluster sampling considered,

3

Results

Between 2 June and 19 June, 1991, we searched 98 plots (Table 1). Kanagayak field camp with 6 people plus a pilot worked on 14 days to cover 59 random plots, the Kokechik River boat crew did 19 plots (plus 2 extra), 3 refuge field camps did 10 plots, and 3 research study camps searched 10 plots. Plot search effort involved 125 person days including the pilot. The sampling effort was similar to 1990 when 101 plots were searched. In 1990, the Kanagayak crew of 6 people worked 12 days to cover 60 random plots, Kokechik River boat crew did 13 plots, Kokechik Bay camp ran 14, and 3 research camps searched 14 plots.

Search of 98 plots resulted in 673 cackling Canada goose, 380 emperor goose, 214 white-fronted goose, 40 spectacled eider nests, and 1060 nests of other species on plots (Table 2).

Total number of nests, number of active nests, and production of eggs

at mid-incubation were estimated for cackling Canada, emperor, and white­fronted geese and spectacled eiders. Comparable data to determine trend in size of nesting populations are available for the 7 coastal strata sampled every year since 1986 (Table 3). Total nests estimated for each strata (Tables 4-7), including those strata sampled only occasionally, showed considerable annual variability due to the large sampling errors of single stratum estimates, nevertheless most individual strata showed similar trends as the entire population.

Cackler production increased by 52%, emperor production by 34%, and white-front production increased by 291 above comparable 1990 estimates. The number of nests increased by 291, 191, and 211 over 1990 estimates for these species. In contrast, Spectacled eider production decreased by 131 and number of nests decreased by 161 compared to 1990. The trend over the last 6 years (Fig. 2) indicated population recovery for geese beginning 1987-1988 and consistent increase, although at differing rates, since that time. An opposite trend was indicated for spectacled eider.

Total numbers of nests and production of eggs for the coastal YK delta were determined by an expansion based on singles and pairs observed (Butler, unpublished data) in all 16 aerial survey strata compared to number observed in the 7 strata sampled by ground plots. Although the 7 sampled strata represent only 221 of the area, 2275 km2 of 12609 km2

, they contain 721 of estimated goose and eider combined 1990 population index. In 1991, the total estimated nests were 43,000 cacklers, 29,000 emperors, 30,000 white-fronts, and 2,300 spectacled eiders (Table 8).

The index to nesting success in 1991 was higher for cacklers and emperors and slightly lower for white-fronts and spectacled eider compared to 1990 (Table 3). Clutch sizes were slightly above those of last year (Table 9).

Float angles on eggs indicated average predicted hatch dates as 22, 20, 21, and 20 June for cacklers, emperors, white-fronts and eiders, respectively (Table 9). These dates averaged slightly earlier than either 1988 or 1990 which were also early years compared to later phenology of nesting in 1986, 1987, and 1989. Trends in nesting phenology, clutch size, or proportion of nests active (Fig. 3), while similar between species among years, show no simple relationship to population size or production.

Discussion:

The number of nests and production increased for _all 3 species of geese. Nesting success was again high with little evidence of loss to arctic fox or avian predators. Geese continued to expand their breeding populations and total production continued to increase rapidly.

4

The combination of environmental conditions and/or management practices has resulted in increased sizes of nesting populations for geese. The trend has been relatively consistent over the last 4 years. Using 1988 to 1991 data for the 7 coastal strata (Table 3), the population growth rate of total nests was calculated for each species by loglinear regression. This procedure smooths out sampling errors and reflects average conditions for the last 4 years. Converting back from the log transformation gives the finite rate of population change as 1.357 for cacklers, 1.177 for emperors, 1.259 for white-fronts, and 0.812 for spectacled eiders. The predicted time for nesting populations to double from their current size, assuming conditions remain the same, is 2.27 years for cacklers, 4.25 years for emperors, and 3.01 years for white-fronts. For spectacled eiders, the population will decline to 501 of current size every 3.32 years.

Comparison of data presented in this report for the 7 coastal strata gives slightly different population values from those reported in the 1990 field report and from previous tabulations based on either 8 strata or a different set of 7 strata. The 7 coastal strata included have been more adequately sampled compared to the lower density and much larger Central Upland stratum. As a result, standard errors on estimates of emperors and white-fronts are smaller. Cackler and spectacled eider estimates are almost unchanged because they rarely occur away from the coast.

Several corrections have been made in 19�6 and 1987 data sets and programs continue to be improved. Only nests found on random plots are included for calculation of average clutch size and timing of nesting. Averages are considered self-weighting; they were not weighted by stratum area, nor were sampled strata constant in all years. Although sample sizes are reduced especially for 1986 and 1987, this makes the data more comparable among years.

Production is estimated as total number of eggs apparently viable in nests found during the second half of incubation. The actual number of young that hatch is reduced by infertile eggs, eggs that do not hatch synchronously, and by loss to predators after the date of visitation. In addition, a large proportion of goslings are lost within a few weeks of hatch. If variability is large among years for these mortality factors, the number of young that survive to the age of fledging or that survive to migrate to wintering areas may not be highly correlated with the early production figures based on egg numbers.

Comparison with data from more intensive biological studies indicates. as expected, that proportion of active nests found overestimates actual nesting success per breeding pair. Reduced detectability of inactive nests, particularly those destroyed or abandoned during laying, causes a smaller proportion of inactive versus active nests to be found, thus causing bias in the estimate. Bias also exists causing underestimation of nest numbers because not all nests are found in a single search of a plot.

The magnitude of these biases are not large and they are assumed to be constant among years.

A primary advantage of the random ground plot sampling procedure is that it can be related to the entire population. The extrapolation based on aerial survey data assumes that visibility, the ratio of nests to singles or pairs observed, average clutch size, and nesting success are comparable in all 16 strata. These are untested but reasonable assumptions. Except for white-fronted geese which occur at low density in interior portions of Yukon Delta NYR, the entire populations of Cackling Canada geese, Emperor geese, and Spectacled eider are represented by the sampling procedure.

s

In order to increase the precision of annual estimates, better allocation of sampling effort would increase the number of plots in the Intermediate strata. Also refinement of stratum boundaries using the accumulated data from all random plots or the 7 years of aerial survey data would be expected to decrease variance. A reduction in ground sampling effort may be reasonable following completion of better stratification and the incorporation of aerial survey data in the analysis.

1991 data were collected by:

Kanagayak:

Kokechik:

Kigigak: Kashunuk: Tutakoke:

Mike Wege, Brain Colter, Tina Moran, Debbie Koziol, Jean Cochrane, Bob Stehn, Fritz Gerhardt, Neil Barten Jimmy Slats, Steve Kendall, Phillip Paniyak, Robin McCartney, Ramone Baccus, Diana May Gene Peltola, Chris Harwood Chris Babcock, Craig Ely, Billy Lincoln, Paul Flint, Dave Boyd Mark Lindberg, Rocky Rockwell, Phillip Kugzruk, Brian Person

6

Table 1. Number of randomly located 0.324 km2 (0.125 mi2 ) plots in various sampling regions of the Yukon-Kuskokwim delta coast that were searched during incubation for waterfowl nests, 1986 to 1991. Strata sampled every year are marked(*).

Region kmz 1986 1987 1988 1989 1990 1991

*Kokechik Bay 100 8 14 19 15 13 9

*Kokechik River 189 7 13 9 11 16 13

*Intermediate 1156 14 14 14 11 16 18

*Tueakoke coast 236 6 9 14 11 14 14

*Hazen Bay 248 7 13 15 10 13 15

*Naskonat Peninsula 274 11 8 11 10 13 14

*Kigigak-Baird Inlet 60 2 3 2 3 3 7

Central upland 1709 9 8 11 10 13 0

Lithkealik River 68 2 l l 2 0 0

North Nelson Island 182 0 4 0 9 0 0

South Nelson coast 399 0 7 0 0 0 8

*Sub-total 2264 55 74 84 71 88 90

Combined 4622 66 94 96 92 101 98

i

Table 2. Number of nests of each species found on random plots.

Species 1986 1987 1988 1989 1990 1991

Cackling Canada Goose 265 268 301 441 513 673 Emperor Goose 158 232 217 322 336 380 White-fronted Goose 63 86 81 112 173 214 Black Brant 111 313 222 1009 427 542 Taverners Canada Goose l 7 4 2 0 2 Tundra Swan 14 17 24 24 28 27 Sandhill Crane 16 24 34 20 47 so

Spectacled Eider 35 48 64 39 40 40 Common Eider 4 14 27 31 14 37

unknown eider 3 17 3 2 1 0 Pacific Loon 28 28 25 33 26 51 Red-throated Loon 5 5 9 2 13 11

unknown loon 2 15 19 10 8 5 Glaucous Gull 30 48 64 43 56 92 Mew Gull 13 19 43 49 25 42 Sabines Gull 9 13 14 15 20 20

Arctic Tern 5 6 7 7 10 8

Northern Pintail 9 19 30 26 14 21 Mallard 0 0 l 0 0 2 Northern Shoveler 1 0 1 2 2 2 Green-winged Teal 2 1 3 4 4 4 Greater Scaup 6 4 10 13 5 4 Oldsquaw 2 8 6 5 4 7 Black Scoter 0 0 l 0 0 0

Canvasback 0 0 0 0 0 1 unknown duck 2 2 2 4 0 0

Western Sandpiper 1 1 11 13 14 15 Ounlin 5 4 7 8 13 17 Bar-tailed Godwit 0 1 1 3 1 l Long-billed Dowitcher 0 0 0 0 0 l

Red-necked Phalarope 18 8 15 26 41 41 Red Phalarope 3 0 2 l 2 3 Black-bellied Plover l 0 1 0 1 3

Black Turnstone 3 5 8 23 13 15 Long-tailed Jaeger 1 1 1 3 1 0

Parasitic Jaeger 1 l 0 1 0 0 Willow Ptarmigan 3 1 4 3 6 9 Lapland Longspur 9 2 3 9 6 13

Savannah Sparrow 3 6 8 19 6 14 Common Redpoll 0 0 l 0 2 0

Combined 832 1224 1274 2324 1872 2367

8

Table 3. Estimated nesting population size and production of eggs at mid-

incubation for geese and spectacled eiders in 7 coastal strata covering

2264 km2 on the Yukon-Kuskokwim delta, Alaska. The 95% confidence interval

is expressed as a percentage of the mean. The nests active at the time of

search divided by estimated total nests determines the proportion active

which is an index to annual nesting success.

Num. Total 95% Active 95% Prop. 951

Year plots nests CI nests Cl active Eggs Cl

Cackling Canada Goose 1986 60 21140 31 13842 34 .655 63920 36

1987 74 15914 28 14756 29 .927 74585 30

1988 84 14009 27 10010 26 . 715 44106 29

1989 71 22505 33 17932 36 .797 85355 36

1990 88 27961 27 21348 29 .763 96735 31

1991 90 36056 22 30490 22 .846 146839 23

Emperor Goose

1986 60 14210 24 10066 26 .708 50842 28

1987 74 15383 26 13688 24 .890 69264 26

1988 84 12443 26 11190 28 .899 53566 28

1989 71 18722 28 17007 27 .908 84716 27

1990 88 18125 20 15414 21 .850 76294 21

1991 90 21659 22 20619 22 .952 102102 24

White-fronted Goose

1986 60 6549 37 6350 38 .970 25399 40

1987 74 6612 37 6140 37 .929 28064 39

1988 84 7105 33 6781 32 .954 29556 31

1989 71 9013 38 8946 38 .993 39168 35

1990 88 11596 26 10942 27 ,944 48965 28

1991 90 14086 32 13119 32 .931 63184 37

Spectacled Eider

1986 60 3798 46 2502 56 .659 10380 62

1987 74 3343 37 2514 41 .752 12287 41

1988 84 3451 45 2984 47 .865 14046 50

1989 71 2424 44 2188 46 .903 10674 43

1990 88 2145 43 1969 45 .918 9834 47

1991 90 1794 44 1586 43 .884 8547 44

•

Table 4. Estimated annual total number of nests for Cackling Canada geese in each sampling region of the Yukon-Kuskokwim delta coast, 1986 to 1991.

Region 1986

*Kokechik Bay 3095

*Kokechik River 4742

*Intermediate 3315

*Tutakoke coast 1703

*Hazen Bay 1973

*Naskonat Peninsula 5472

*Kigigak-Baird Inlet 841

Central upland 1760

Lithkealik River 0

North Nelson Island

South Nelson coast

*Sub-total 21140

*Annual% change

Combined 22900

Standard error 3607

Relative 95% C.I. 31

Lower 95% C. I. 15831

Upper 95% c. I. 29970

1987 1988

1282 2167

941 712

1275 1275

3081 3492

3659 1176

2438 2852

3238 2335

0 0

0 0

0

1584

15913 14009

·25 -12

17497 14009

2309 1896

26 27

12972 10292

22023 17726

1989

3467

2382

649

4113

2992

5850

3051

0

211

312

22505

+61

23028

3774

32

15631

30425

1990 1991

3024 3508

1347 1120

4685 9321

6464 5004

3482 5371

3978 7570

4981 4163

1624

2617

27961 36056

+24 +29

29585 38674

4107 4257

27 22

21535 30329

37635 47018

9

10

Table 5. Estimated annual total number of nests for Emperor geese in each sampling region of the Yukon-Kuskokwim delta coast, 1986 to 1991.

Region 1986 1987 1988 1989 1990 1991

*Kokechik Bay 1238 1039 1124 1940 1738 1479

*Kokechik River 1664 896 906 1271 2038 1702

*Intermediate 3315 2550 2805 3245 3123 4759

*Tutakoke coast 973 1054 1407 1858 2189 834

*Hazen Bay 3069 2951 1535 3376 3895 5371

*Naskonat Peninsula 3391 5087 3546 5850 3522 6419

*Kigigak-Baird Inlet 560 1806 1121 1183 1619 1094

Central upland 2933 1320 2400 2640 2030

Lithkealik River 211 0 632 105

North Nelson Island 703 1750

South Nelson coast 1408 1078

*Sub-total 14210 15383 12443 18722 18125 21659

*Annual I change +8 -19 +SO -3 +19

Combined 17354 18813 15475 23217 20156 22737

Standard error 2159 2509 2221 3308 1946 2493

Relative 951 C.I. 24 26 28 28 19 22

Lower 95% c.r. 13123 13896 11121 16733 16341 17851

Upper 951 C.I. 21585 23730 19828 29700 23970 27622

11

Table 6. Estimated annual total number of nests for White-fronted geese in each sampling region of the Yukon-Kuskokwim delta coast, 1986 to 1991.

Region

*Kokechik Bay

*Kokechik River

*Intermediate

*Tutakoke coast

*Hazen Bay

*Naskonat Peninsula

*Kigigak-Baird Inlet

Central upland

Lithkealik River

North Nelson Island

South Nelson coast

*Sub-total

*Annual% change

Combined

Standard error

Relative 951 C.I.

Lower 951 C. I.

Upper 951 C. I.

1986 1987

232 221

499 538

2040 1785

730 487

1644 826

1310 2755

93 0

1173 0

105 0

844

880

6549 6612

+l

7827 8335

1454 1467

36 35

4977 5459

10678 11211

1988 1989 1990 1991

130 392 143 447

712 794 837 358

3570 2921 3346 5156

678 796 1616 1251

1074 1611 3187 3274

848 2374 2217 3573

93 125 249 27

480 0 2437

0 316

187

2925

7105 9013 11596 14086

+7 +27 +29 +21

7585 9516 14033 17011

1279 1762 2246 2400

33 36 31 28

5079 6063 9629 12307

10091 12969 18436 21716

Table 7. Estimated annual tocal number of nests for Spectacled Eider in each sampling region of the Yukon-Kuskolcwim delta coast, 1986 to 1991.

Region

*Kokechik Bay

*Kokechik River

*Intermediate

*Tutakoke coast

*Hazen Bay

*Naskonat Peninsula

*Kigigak-Baird Inlet

Central upland

Lithkealik River

North Nelson Island

South Nelson coast

*Sub-total

*Annual% change

Combined

Standard error

Relative 951 C. I.

Lower 951 C.I.

Upper 951 C. I.

1986 1987

155 420

250 90

765 255

973 0

329 1239

1233 530

93 809

0 0

0 0

0

704

3798 3343

-12

3798 4047

900 817

46 40

2035 2446

5561 5648

1988 1989 1990 1991

440 124 119 69

0 159 0 45

765 0 0 0

1043 796 1147 626

307 384 236 512

617 339 457 303

280 623 187 240

0 0 0

0 0

62

154

3451 2424 2145 1794

+3 -30 -12 -16

3451 2487 2145 1948

797 544 465 428

45 43 43 43

1889 1421 1233 1109

5013 3552 3057 2786

12

13

Table 8. Annual nesting population and production based on estimated number of nests and eggs in the 7 coastal strata sampled by ground plots expanded in proportion to aerial survey obser·ations of singles and pairs made in 7 sampled strata compared to all 16 scrata.

Prop. of Total nests Total eggs

Year air obs. sampled expanded sampled expanded

Cackling Canada Goose

1986 .839 21140 25197 63920 76186 1987 .793 15914 20068 74585 94054 1988 .850 14009 16481 44106 51889 1989 .844 22505 26665 85355 101132 1990 .837 27961 33406 96735 115573 1991 ,837 a 36056 43078 146839 175435

Emperor Goose

1986 .660 14210 21530 50842 77033 1987 .640 15383 24036 69264 108225 1988 .733 12443 16975 53566 73078 1989 .766 18722 24441 84716 110595 1990 .735 18125 24660 76294 103801 1991 .735 a 21659 29468 102102 138914

�ite-fronted Goose

1986 .454 6549 14425 25399 55945 1987 .411 6612 16087 28064 68282

1988 .487 7105 14589 29556 60690 1989 .454 9013 19852 39168 86273 1990 .464 11596 24991 48965 105528 1991 ,464 • 14086 30358 63184 136172

Spectacled Eider

1986 . 780 • 3798 4869 10380 13308 1987 , 780 a 3343 4286 12287 15753 1988 ,538 3451 6414 14046 26108 1989 . 774 2424 3132 10674 13791 1990 .780 2145 2750 9834 12608 1991 .780 • 1794 2300 8547 10958

• Proportion based on 1990 data.

14

Table 9. Average active clutch size, date of hatch. and proportion of

nests remaining active at the last visit (usually the only visit) based

only on nests found on random plots.

Active Clutch Hatch Date Prop. Nests

avg. n avg. n Active n

Cackling Canada Goose

1986 4. 34 168 June 29,l 143 ,634 265

1987 4.79 242 June 28.2 78 .903 268

1988 4.45 227 June 23.4 69 .757 301

1989 4.64 376 June 30.0 51 .853 441

1990 4.51 386 June 23.3 166 .752 513

1991 4.58 581 June 22.1 343 ,863 673

Emperor Goose

1986 5.25 104 June 27.9 95 .658 158

1987 5.03 216 June 27.7 90 ,931 232

1988 4.88 190 June 21.6 56 .876 217

1989 5.01 296 June 30.3 60 .919 322

1990 4. 77 286 June 21.0 86 .851 336

1991 4.93 355 June 19.8 248 .934 380

White-fronted Goose

1986 4.00 53 June 27.6 39 .841 63

1987 4.18 78 June 27.6 41 .907 86

1988 4.36 74 June 23.5 25 .914 81

1989 4.40 109 June 26.0 16 .973 112

1990 4. 34 164 June 22.0 43 .948 173

1991 4.46 198 June 20,6 123 .925 214

Spectacled Eider

1986 3,68 30 June 27.9 19 .789 38

1987 4.54 59 June 29.7 16 .908 65

1988 3.92 51 June 26.8 15 .761 67

1989 3.92 36 June 30.9 4 .878 41

1990 3.89 38 June 23.l 12 • 927 41

1991 4.32 38 June 20.2 25 .950 40

13

l. Rokechik Bay2. Rokechik River3. Intermediate4. Tutakoke coasts. Hazen Bay6. Naskonat peninsula7. North Nelsone. south Nelson9. Helson-Kipnuk upland10. central upland11. Scammon-Black coast12. Scammon-Black upland13. south Yukon14. Horth Yukon15. coastal uplands16. Kigigak-Baird Inlet17. Lithkealik River

Figure 1. Location of sampling strata for both ground based random plots and aerial survey transects on the coast of the Yukon-Kuskokwim delta.

50000

! Cackling40000 .1-

t

0

Emperor

i 30000

White-front CD

I z 20000

tt yt? If

???1? t

SpectacledEider

10000

9¢9¢¢0 0

86 87 BB 89 90 91 86 87 BB 8990 91 86 87 88 899091 8687 BB 899091

200000.....-------------------,

160000

u, 120000'" C) C)

80000

40000 ·-

Cackling ) Emperor

) White-front

Spectacled Eider

9¢9¢¢¢ OJ.._ ________________ ___.

Figure 2. Annual estimates and 95 I confidence intervals for total nests and

total eggs in 7 coastal strata sampled from 1986 to 1991.

Cackling

Q) 1 l ;

j\,�1 ;}_ .9

C: .8 0·-

.7 0

.6 ea.

.5

�5.5

·-en

..c:

tv� (.J 4.5

u

3.5

CD 30

V\ ca Cl

25

ca 20 :::c

June 15

86 87 88 8990 91

Emperor

0 ('!

Q

�

86 87 88 8990 91

White�front

a/' ' 0-.....;

86 87 88 899091

Spectacled

Eider

�

I

/v

86 87 88 89 9091

Figure 3. Trend among species and years in proportion of nests found active, average active clutch size, and predicted date of hatch.