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Grays Lake Ecosystem

Earlier Studies at Grays Lake

Beiswenger, J. M.  1991.  Late Quaternary vegetational history of Grays Lake,
     Idaho.  Ecological Monographs 61:165-182.

Sediment cores were taken from the center of Grays Lake Marsh and from the southern edge. Analyses of pollen in the cores indicate cold, dry conditions existed in the valley from ~70,000 to 30,000 years BP when an Artemisia steppe surrounded Grays Lake and extended into the nearby mountains. Somewhat moister conditions supporting a conifer woodland occurred from ~30,000 to 11,500 years BP. A cool transitional climate occurred ~11,500 years BP as indicated increases in Picea, Abies, and Artemisia. As the climate became warmer and drier, Juniperus and members of Chenopodiaceae/Amaranthaceae and Compositae families became more abundant. Xeric conditions persisted from ~10,000 to 7,100 years BP. Climate at Grays Lake subsequently has been cooler and moister, with decreases in Juniperus and steppe plants and increases in conifers.

Drewien, R. C., and K. R. Klegg.  1992.  Capturing whooping cranes and sandhill
     cranes by night-lighting.  Proceedings of the North American Crane Workshop 

Greater sandhill cranes at Grays Lake were captured during 1981-91 using night-lighting techniques to band and color-mark them for research studies. These techniques were also used to capture adult whooping cranes in Idaho, Wyoming, and New Mexico. At Grays Lake, 157 adult sandhill cranes and 93 juvenile sandhill cranes were captured using a portable generator mounted on an aluminum backpack frame, a 12- or 28-V spotlight mounted on a helmet, and a large, long-handled fish landing net. Capture success was influenced by presence of other avian species, habitat type, weather, and nocturnal conditions (e.g., moon phase, amount of starlight). Success was greatest when cranes were roosting with few other cranes or other aquatic birds and during overcast or inclement nights. Although safe and effective, it is a strenuous technique to capture cranes.

Drewien, R. C., and E. G. Bizeau.  1977.  Cross-fostering whooping cranes
     to sandhill crane foster parents.  Pages 201-222 in S. A. Temple, ed.  
     Endangered birds:  management techniques for preserving threatened species.
     University of Wisconsin Press, Madison, WI.

The Canadian Wildlife Service and U.S. Fish and Wildlife Service began a cooperative experiment in 1975 to reintroduce whooping cranes into the Rocky Mountain region of the United States. Eggs from wild whooping cranes were collected in Wood Buffalo National Park, Northwest Territories, and placed in nests of greater sandhill cranes at Grays Lake National Wildlife Refuge. This experiment at Grays Lake was designed to evaluate the technique of cross-fostering whooping cranes to sandhill cranes. This paper describes the progress of the experiment from May 1975 through August 1977; for final results of this experiment see Garton et al. 1989. Sandhill crane pairs that had histories of high hatching success and fledging rates, nested in areas that were relatively free from human disturbance, and wintered at Bosque del Apache National Wildlife Refuge, New Mexico, were selected as foster parents. Eggs from whooping cranes at Wood Buffalo National Park (n=45) and from captive cranes at Patuxent Wildlife Research Center, Maryland (n=16) were transported by air to Grays Lake during 1976 and 1977. In each foster nest, 1 whooping crane egg was substituted for crane eggs. Young whooping cranes were captured, banded, and color-marked in August each year, and their movements, migration, and survival monitored. Of the 45 eggs received from Wood Buffalo, 35 hatched, 6 were lost to predators, and 4 were addled or infertile. Of the 16 eggs from Patuxent, 5 hatched, 6 were addled or infertile, 3 were deserted due to snowstorms, and 2 were lost to predators. Foster pairs readily accepted hatched young regardless of duration of incubation, which varied widely. Activities and interactions between foster young and parents appeared normal. None of the young from 16 eggs originating from Patuxent fledged, and 13 of the eggs from Wood Buffalo fledged. Percentage of young that fledged paralleled declines in water levels, general habitat conditions, and sandhill crane production during the 3-year period. Sources of mortality of prefledged and fledged young are described. Foster-parent families successfully migrated to wintering areas in the middle Rio Grande Valley, New Mexico and returned to Grays Lake via San Luis Valley, Colorado each spring. Excessive mortality of young prior to fledging was a major problem was related to drought conditions during 2 of the 3 years. An intensive predator control program was planned for later years of this experiment.

Drewien, R. C.  1973.  Ecology of Rocky Mountain greater sandhill cranes. 
     Ph.D. Dissertation, Univ. Idaho, Moscow.  152pp.

This study examined the status, reproduction, and distribution of the greater sandhill crane (Grus canadensis tabida) at Grays Lake during 1969-1971. May aerial counts indicated 554 and 544 cranes in 1970 and 1971, respectively. An estimated 250 pairs nested at Grays Lake; the high nesting density of 200 pairs within a 10,000 ha area is the highest density reported for cranes in North America. Most of the 337 nests located were located in wet meadow/marsh zones along the bulrush/cattail edge; 56% were in water when first located and 44% were on dry ground. Nest site locations and construction are described. Egg-laying began in late April or early May; incubation was estimated at 30 days. Mean clutch size was 1.94 eggs and included 24 one-egg and 3 three-egg nests. Nest success was 78% (n=308 nests over 3 years). Nest predation was the primarily cause of nest losses. Mean brood sizes at hatching and fledging were 1.77 and 1.35, respectively. Behaviors of incubating and brooding cranes and defense of breeding territories are described. July aerial surveys were not successful for providing information on production. Fall counts provided a description of fall staging and migration and habitat use. Peak counts in mid-September indicated 1,236 and 1,390 cranes in 1970 and 1971, respectively; fall flocks contained 16 juveniles/100 adults. Use of grain fields by cranes increased from early August to mid-September then declined with migration out of the valley. Sighting of color-marked cranes provided information on spring and fall arrival of individuals, immigration of individuals to Grays Lake in fall from areas 15-25 km away, and movements of individuals through the San Luis Valley, Colorado and to main wintering areas in western New Mexico, southeastern Arizona, and northern Mexico. The Rocky Mountain Population of greater sandhill cranes was estimated at 10,000-15,000.

Mullins, W. H., III.  1974.  Summer food habits of the greater sandhill crane
     (Grus canadensis tabida) at Grays Lake, Idaho.  M.S. thesis, University of 
     Idaho, Moscow.  12pp.

Food habits of 20 greater sandhill cranes collected at Grays Lake in June-July, 1972 and 1973 at Grays Lake were evaluated. Results include foods in esophagus, proventriculus, and gizzard; most food was found in the gizzard. Plants comprised 73% of total volume. Timothy corms (Phleum pratense) were the most prevalent food (in 11 cranes; 68% total volume). Other plants consumed (<2% total volume) included grass rachises, horsetail (Equisetum spp.), barley, and seeds of lupine (Lupinus) and broad-fruited burreed (Sparganium eurycarpum). Insects and worms comprised 27% of total volume. The predominant animal food was short-horned grasshoppers (Melanoplus sanguinipes; 7 cranes, 11%of total volume). Other frequently found animal foods found were fly larvae (Sarcophagidae; 3 cranes, 6% total volume), cutworms (Agrostis vetusta, 8 cranes, 1% total volume). Other animal foods found in <3 cranes were narrow-winged damselflies (Coenagrionidae), carrion beetles (Silpha ramosa), click beetles (Ctenicera carbo), earthworms (Oligochaeta), robber flies (Cyrtopogon sp.), and ichneumon wasps (Compsocryptus sp.). Observations of foods consumed and foods available to cranes in this and other studies indicate sandhill cranes are omnivorous and opportunistic feeders.

Steel, P. E., P. D. Dalke, and E. G. Bizeau.  1956.  Duck production at Gray's
     Lake, Idaho, 1946-51.  Journal of Wildlife Management 20:279-285.

Waterfowl production at Grays Lake was examined during April-October, 1949-1951. The waterfowl breeding population was estimated at 15,000 ducks in 1949, 12,000 in 1950, and 10,000 in 1951. Breeding ducks include mallards (Anas platyrhychos), northern pintails (A. acuta), cinnamon teal (A. cyanoptera), blue-winged teal (A. discors), gadwall (A. strepera), northern shovelers (A. clypeata), green-winged teal (A. discors), canvasbacks (Aythya valisineria), redheads (A. americana), lesser scaup (A. affinis), and ruddy ducks (Oxyura jamaicensis). Mallards and pintails comprised approximately 50% of dabbling ducks, and canvasback and redheads were the predominated diving ducks present. Apparent nest success of all species averaged 70% during this 3-year study. For each species, distribution of nests among habitats, apparent nest success rates, clutch size, egg success rates, and average brood sizes for Class I, II, and III are reported. Over 60% of the nests were found in the southeastern portion of the Grays Lake basin. Bulrush and cattail were most important for diving ducks but also held 37% of mallard nests; 97% of all duck nests in all marsh habitats were within 15 yards of the nearest open water. Nests of dabbling ducks were most commonly found on islands, along the lakeshore, and in upland fields. Nest losses were attributed to mammalian predators (29%), avian predators (22%), grazing (3%), unknown predator (7%), and desertion (28%). Overall duck production was estimated as 47 nests/100 habitat acres in 1949, to 39 nests in 1950, to 15 nests in 1951. Waterfowl mortality due to spring muskrat trapping was estimated at 1-2%, while 14-18% of the American coot (Fulica americana) population was trapped in 1950-1951, respectively.

Steel, P. E., P. D. Dalke, and E. G.  Bizeau.  1957.  Canada Goose production at 
     Gray's Lake, Idaho, 1949-1951.  Journal of Wildlife Management  21:38-41.

Nesting and populations of Canada geese in the Grays Lake marsh were examined during 1949, 1950, and 1951. Most nests were initiated in mid-late April, before the marsh was free of ice and snow. A total of 380 nests were located; 77% were on muskrat houses, of which 63% were on active houses. Only 2% of nests were located on cattail islands. Overall, 80% of nests were built in cattail, bulrush, or a combination of these cover types. Of 361 goose nests, 80% were successful. Land nests and marsh nests were equally successful. Fifteen percent of all terminated nests were deserted for unknown reasons, but some nests were frequently disturbed by spring muskrat trappers. Average clutch size for the 3 years was 5.2. Egg success ranged from 83 to 91% and averaged 86%. Average hatch per nest varied from 4.2 in 1949 to 4.6 in 1951. Following spring censuses of about 800 and 1,000 breeding and nonbreeding geese in 1950 and 1951, the total hatch was estimated at to 990 and 1,010 goslings, respectively.

Wigand, P. E. 1999.  Local marsh and regional fire history and environmental
     context as reconstructed from sediment cores at Grays Lake, Idaho.   
     Unpubl. rep.

Sediment cores taken from Grays Lake were examined using radiocarbon-dating techniques to reconstruct a record of fire recurrence and history for the last 2,000 yrs. Five 5-m long cores were taken from two localities in the northern half of the marsh. Radiocarbon dates from the cores indicate that at least 10,000 years are represented. Examination of cores from location 2 indicates fire, as measured by charcoal abundance, was much more common in the marsh between 1,000 and 1,900 years ago and during the last 300 years than it was during other times during the last 2,000 years. Increased fire severity and probably frequency seems to be associated with a summer shifted, highly variable period of climate between 1,900 and 1,000 years ago. Occurrence of fire in the marsh is inversely related to productivity (as measured by organic weight). Increased fire clearly follows the onset of periods of lower marsh productivity and periods of lower aquatic plant diversity likely associated with drier periods (as indicated by aquatic pollen types). Fire appears to have been more prevalent between 4,000 and 7,000 years ago than it has been in the last 4,000 years. During the last 2,000 years, rising water table, high productivity, and burial and decay of plant materials has been more important in recycling nutrients in the marsh than fire has been. During the last 2,500 years the water table has risen by >1.5 m. Fire has been more prevalent in the marsh since the end of the “Little Ice Age” than it has been for most of the last 1,000 years. Recent declines in fire may be related to fire suppression, but it is impossible to determine the role of humans in promoting fire in the marsh.

Williams, R. M.  1950. A preliminary investigation of the muskrat population
     of Gray's Lake, Idaho.   M.S. thesis, Univ. Idaho.  69pp.

Muskrat populations and spring trapping harvest at Grays Lake were studied during the late 1940s. In spring and fall seasons in 1948, 35 trappers removed an estimated 10,000 muskrats. In spring 1950 5,325 muskrats were harvested; only a fraction of the total lake area was trapped. Counts of muskrat houses in 1949 indicate a breeding population of 8,140 and a winter population of 35,200 muskrats. Losses during winter were believed to be relatively light. Reproduction period (births) extended from late May to mid-August, with peaks in late June-early July. Litter sizes averaged nearly 7 (range 2-11). Average total production per female was 10.4 young, of which 84% survived to December. Marking of individual muskrats indicated summer and fall movements were confined to small areas; 75% of recaptures were within 50 yards of the original tagging site. Maximum distance moved was 200 yards. In spring, males averaged 909 g and females 837 g in weight. Average growth of juveniles was 47 g/month. Sex ratios remained fairly constant from litter through adults, indicating no differential sex mortality. No serious diseases or ectoparasites were evident during this study. During the 10-day spring (April) muskrat trapping season, trappers caught 1 goose, 27 ducks, and 173 coots.

Zielinski, G. A.  1980.  An analysis of the morphology, hydrology and climate 
     of the Grays Lake drainage basin, Bonneville and Caribou counties, Idaho.  
     M.S. thesis, Idaho State University, Pocatello, ID.

Gemorphological and hydrological conditions at Grays Lake, Idaho were examined to provide baseline data for determination of past sedimentation processes as defined in Olivier (1980). Grays Lake offers one of the few sites in the Northern Rocky Mountains to provide an uninterrupted Quaternary lacustrine record during both glacial and interglacial periods. Present morphological conditions reflect initial channel development during the late Tertiary. Valley infilling occurred during wetter glacial periods and valley incisions occurred during interglacial periods. The valley changed from fluvial to lacustrine deposition when late Pleistocene basalt flows dammed the valley. Basin and channel development in five individual basins were examined. Hydraulic geometry varied among 4 drainages examined. Eagle, Gravel, and Creek A [North Crane Creek] showed greater changes in depth and velocity with changes in discharge whereas Creek B [South Crane Creek] showed greater changes in width with discharge.

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