Midcontinent Population Research Articles

Response of nesting savannah sparrows to 25 years of habitat change in a snow goose colony

Duplication of a study conducted 25 years earlier reveals that the number of savannah sparrows nesting adjacent to the coastal salt marshes of La Pérouse Bay in northern Manitoba, Canada, has declined by 77%. This decline coincides with a 63% reduction in vegetation cover in the bird’s preferred grassland-shrub habitat. The habitat degradation resulted from processes associated with destructive foraging by the increasing mid-continent population of lesser snow geese during their breeding season. Growth of this snow goose population has been initiated and sustained by a series of anthropogenic factors operating primarily on the snow goose wintering grounds, far south of these Arctic coastal habitats. Thus, the indirect human impact on nesting by savannah sparrows is the result of a complex chain of ecological events operating on connected habitats across a large geographical expanse. Mitigation of such effects and an assessment of the impacts in general must take into account such complexities.

Mitochondrial DNA Variation among Wintering Midcontinent Gulf Coast Sandhill Cranes

Based on morphological characteristics, 3 subspecies of sandhill cranes (Grus canadensis)-the lesser sandhill crane (G. c. canadensis), Canadian sandhill crane (G. c. rowani), and greater sandhill crane (G. c. tabida)-occur within the midcontinent population (MCP) and winter along the Gulf Coast of Texas, USA. Of these subspecies, the greater sandhill crane is the least abundant and the most restricted in distribution in the midcontinent region, making it a subspecies of special concern. Twenty individuals from each subspecies with the highest posterior probabilities of membership in subspecies associated with their morphological discriminant score (i.e., those individuals that were least likely to be misclassified based on the morphological model currently used to assign wintering individuals to subspecies) were chosen from a total sample of 220 birds. We amplified and sequenced a 437-base-pair segment from domain I of the mitochondrial DNA (mtDNA) control region for these 60 birds. Analyses of the resulting 41 different mtDNA haplotypes indicate that birds classified as Canadian and greater sandhill cranes based on their morphology do not differ genetically, but lesser sandhill cranes are genetically distinct from both Canadian and greater sandhill cranes. When Canadian and greater sandhill cranes are grouped together, 55 of the 60 individuals sequenced are consistently classified using morphology and mtDNA. We then used the DNA sequences to develop a simple restriction enzyme assay of this mtDNA segment to survey an additional 160 specimens. These results indicate that (1) mtDNA assays provide reliable discrimination of migratory sandhill cranes, (2) the current subspecific designations of sandhill cranes may not accurately reflect genetic structure in this species, (3) concern for preserving the genetic diversity of sandhill cranes in the midcontinent region may not need to focus on management of greater sandhill cranes wintering in the sampled populations, and (4) studies of individuals from the breeding grounds are clearly needed to determine whether Canadian and greater sandhill cranes are indeed distinct subspecies.

Arctic Climate, Spring Nutrition, and Recruitment in Midcontinent Lesser Snow Geese

I examined fall age ratios of midcontinent lesser snow geese (Chen caerulescens) shot by hunters in the Central and Mississippi flyways (1962-1999), and spring nutrient reserves in southern Manitoba, Canada (Apr-May, 1983-1984, 1988-1993). Age ratios were inversely related (95%[β S ] = -0.170 ± 0.068) to severity of arctic weather as indexed by average snow depth during May and June, and mean June temperatures. After accounting for this effect, age ratios declined 0.017 ± 0.009 immatures/adults/year during 1962-1999. Body size, indexed by principal components analysis of 10 morphological measures, declined -0.082 ± 0.057 per year during 1983-1993. Body mass, fat, protein, and mineral reserves showed considerable annual variation, but only mass (9.8 ± 1.6 g/day) and body fat increased during spring staging in Manitoba; rate of increase in body fat ranged from 6.0 ± 2.9 g/day during 1990 to 17.5 ± 3.8 g/day during 1993. Using model-averaged estimates from a set of candidate models, fall age ratios (controlling for differences between flyways and annual severity of arctic spring weather) were related to body mass (0.0011 ± 0.0008 immature/adult/g), and fat during early staging during April (0.00092 ± 0.00072 immatures/adult/g), but the relationship with body fat during late staging in May was not as strong (0.00020 ± 0.00022 immatures/adult/g); age ratios were unrelated to variation in protein or mineral reserves. Linkages between recruitment in the Arctic and nutritional state on the prairies the previous spring suggest that management on spring staging areas could influence dynamics of the midcontinent population of lesser snow geese, and perhaps of other Arctic-nesting goose populations.

Intertidal plant communities of an Arctic salt marsh: The influence of isostatic uplift and herbivory

Recently, the mid-continent population of lesser snow geese has increased at about 7% per year and increased numbers of geese have adversely affected the vegetation of intertidal communities on the shores of Hudson and James Bays. A quantitative description of plant communities was undertaken before they are modified or lost as a result of the direct and indirect effects of goose foraging. The region is undergoing isostatic uplift and salt marshes have developed on the extended, low elevation shorelines. The site chosen for the study was La Pérouse Bay, Manitoba, where there is a breeding colony of lesser snow geese. The plant assemblages recognised in intertidal zone, based on the use of Canonical Correspondence Analysis, were the Puccinellia-Carex community, the Festuca-Calamagrostis community (both of which were grazed and grubbed by geese), bare sediment, and the Hippuris-Myriophyllum assemblage characteristic of brackish aquatic habitats (rarely grazed by geese). The communities were primarily differentiated in terms of elevation, water depth, and area of plant cover. These communities are widespread elsewhere in intertidal areas adjacent to the Hudson Bay lowlands, but intensive goose foraging has led either to their loss or to fine-scale fragmentation with little likelihood of revegetation in the foreseeable future. This description of vegetation serves as a baseline against which further changes can be monitored and assessed.

Vulnerability of Lesser Snow Geese to Hunting with Electronic Calling Devices

The Arctic Goose Habitat Working Group recommended several management actions, including use of electronic calling devices, to reduce the mid-continent population of lesser snow geese (Chen caerulescens caerulescens; hereafter snow geese). We compared the vulnerability of snow geese to hunting with electronic calling devices and traditional calling methods (hand-held and voice calls) with cooperative goose hunters (96 commercially guided and 47 non-guided hunters) during the 1997-98 snow-goose-only seasons in Louisiana, Arkansas, and Iowa. We found that snow goose flocks were 5.0 times more likely to fly within gun range (≤50 m) in response to electronic calls than to traditional calls. Mean size of snow goose flocks that flew within gun range during electronic calling periods averaged 1.8 times larger than that during traditional calling periods. Mean number of snow geese killed/hr/hunter averaged 9.1 times greater for electronic calls than that for traditional calls. Ages of harvested snow geese were similar between calling methods (P = 0.12), but differed among states (P < 0.05) and between sexes (P < 0.05). Adult snow geese were 1.7 times more likely to be shot in Louisiana than in Iowa and 1.8 times more likely to be shot in Arkansas than in Iowa. Relative to their juvenile counterparts, adult males were 1.5 times more likely to be shot than were adult females. Body condition (body mass adjusted for size) generally was greater for snow geese killed during electronic calling periods than that during traditional calling periods. Flock response, kill/hr/hunter, and adult body condition of harvested snow geese generally decreased, whereas observed flock size increased from south to north, i.e., from Louisiana to Iowa. Our results indicated that snow geese are more vulnerable to electronic calls than to traditional calls. Finally, our calculations suggested that use of electronic calls during current snow-goose-only season frameworks (i.e., before 10 March) alone will not achieve desired population reduction goals for the mid-continent populatibn of snow geese.

Use of Wetland and Deepwater Habitat by Wintering Sandhill Cranes in Coastal Texas

es, coastal prairie, scrub oak brushland, and harvested grain fields (Guthery, 1975). Sandhill cranes roost on shallow open water marshes in coastal Texas (Guthery, 1975), saline lakes in west Texas (Iverson et al., 1985), and shallow rivers and lakes in New Mexico (Walker and Schemnitz, 1987). However, data are lacking on the types of wetlands and deepwater habitats important to sandhill cranes. Low recruitment rates in the mid-continent population emphasize the need for close monitoring of populations and habitats (Tacha et al., 1992). Our objective was to determine the most important wetland and deepwater habitat types, based on density, for wintering sandhill cranes along the Texas Gulf Coast. We conducted the study from Galveston Bay, Texas south to the Rio Grande River, an area of 55,000 km2 (Anderson et al., 1996, 1998). This area corresponds to the region occupied by the Gulf Coast subpopulation of sandhill cranes (Tacha et al., 1992). The region is predominantly rice fields and coastal marsh in the northeast and coastal prairie and sandy plains in the southeast (Anderson et al., 1996). Palustrine and estuarine wetlands and deepwater habitats (Cowardin et al., 1979) are common (Muehl et al., 1994). We conducted ground surveys of all flooded wetlands and deepwater habitats on 512 randomly located, 64.75-ha plots in 1991-1992 and 1,009 plots in 1992-1993 (Anderson et al., 1996, 1998) for sandhill cranes. Surveys were conducted throughout the day during 2 week periods in September, November, January, and March as part of a larger project investigating habitat use by other waterbirds (Anderson, 1994; Anderson et al., 1996), waterbird abundance (Anderson et al., 1998), and wetland abundance (Muehl et al., 1994). The wetlands surveyed are representative of habitat conditions and wetland types found throughout most of the Gulf Coast (Anderson, 1994). All suitable habitat was surveyed for sandhill cranes to estimate populations (Anderson et al., 1998), but only cranes observed on wetlands and deepwater habitats are included in this paper. Few sandhill cranes were observed in September and March (Anderson, 1994), so we only present data for November and January. We classified all wetlands and deepwater habitats on plots according to Cowardin et al. (1979) by recording system, subsystem, class, and subclass. We recorded wetland size as the

The detection of vegetational change by multitemporal analysis of LANDSAT data: the effects of goose foraging

1 The North American mid‐continent population of lesser snow geese now exceeds 3 million birds and the population is increasing in the order of 7% per annum. The foraging activities of the birds on Arctic breeding grounds are leading to loss of vegetation and habitat destruction, particularly in coastal areas bordering the Hudson and James Bays. 2 Multitemporal analysis of LANDSAT data has been carried out to detect vegetational change from 1973 to 1993 at La Pérouse Bay and its vicinity, the site of a breeding colony of snow geese. 3 Difference vegetation images (DVI) (difference between infra‐red and red images) were prepared from images obtained in late summer in 1973, 1984 and 1993, in order to enhance vegetation density. Pair‐wise differences were calculated between these DVI images, which resulted in three, secondary, classified images. Classification of the three secondary images (1973–84, 1984–93, 1973–93) yielded three well‐defined classes: water, vegetation decline and no change in vegetation. 4 Histogram counts gave the following values for areas of vegetation decline: 1973–84, 1026 ha; 1984–93, 1428 ha; 1973–93, 2454 ha. 5 The loss of vegetation and the destruction of habitat are discussed in relation to the foraging activities of the expanding goose population.

Long-term destruction of sub-arctic wetland vegetation by lesser snow geese

:During the last two decades, the mid-continent population of lesser snow geese (Anser caerulescens caerulescens), which breeds in the Canadian eastern Arctic, has increased dramatically to at least 3 million birds. In spring, the birds follow the retreating snowline northwards to the breeding grounds. They forage intensively on shoots of sedges just south of the snowline, eating the swollen shoot bases and discarding the remainder. Exclosures were established in 1985/86 at La Pérouse Bay, Manitoba to determine the effects of protection from foraging on the shoot densities of sedges. Between 1986 and 1995, numbers of shoots increased from 1.1 to 2.2 times in exclosed plots, while numbers in grazed plots declined to between 0.19 and 0.33 times their original values. Sedge assemblages were replaced by moss carpets or standing water rich in peat debris. The ecological significance of the results is discussed in relation to re-establishment of vegetation and the role of herbivores in changing species assemblages.

Distribution and Abundance of Sandhill Cranes in Mexico

We summarized sandhill crane (Grus canadensis [cranes]) counts from Mexico recorded during 23 January aerial waterfowl surveys by the U.S. Fish and Wildlife Service (FWS) between 1953 and 1994. Cranes were recorded at 39 areas in 14 states ; 97.4% were in the Northern Highlands, 0.4% in the Central Highlands, 1.5% along the Gulf Coast, and 0.7% on the Pacific Coast. Most wintered in the states of Chihuahua (91.7%) and Durango (4.7%). Total counts of >30,000 cranes were recorded in 1979 and 1994 ; 70,000 were reported in Chihuahua in February 1947. Laguna de Babicora, Chihuahua, was the most important winter area. We also conducted ground and aerial surveys in Chihuahua during most winters 1970-92 and occasionally in Durango and Sonora. We found a mean of 21,649 cranes at 6 study areas in Chihuahua with highest mean counts at Laguna de Babicora (16,012), followed by Ascension (2,405) and Laguna de los Mexicanos (1,469). Our surveys indicated that >50,000 cranes winter in Mexico. At 6 study areas in Chihuahua, all 3 migratory subspecies were present with the lesser subspecies (G. c. canadensis [lessers]) composing 88.9%. The greater (G. c. tabida [greaters]) and Canadian subspecies (G. c. rowani [Canadians]) composed the remainder but could not be differentiated in field surveys ; about 25% of cranes classified as greaters may have been Canadians. Annual recruitment and brood size averaged 10.1% and 1.18 in lessers and 6.5% and 1.14 in greaters. Lessers and Canadians wintering in the Interior Highlands belong to the Western Subpopulation of the Midcontinent Population (MCP), while greaters are from the Rocky Mountain Population (RMP). Based on sightings of marked cranes, band recoveries, and field observations, we estimated that about 10% of the RMP wintered in Mexico in Chihuahua and Durango. RMP cranes were more abundant in northern Chihuahua than at sites farther south (P < 0.001). Gulf Coast cranes are probably Canadians and lessers from the MCP, Gulf Coast Subpopulation. Population affiliations of Pacific Coast cranes are uncertain. Laguna de Babicora, the most important crane wintering area in Mexico, is threatened by proposed habitat alterations. Loss of this wetland would adversely affect cranes and other migratory birds, including several endangered species. Conservation plans and action are needed to protect this key winter site.

Recruitment in Rocky Mountain Greater Sandhill Cranes and Comparison with Other Crane Populations

The sandhill crane (Grus canadensis) has the lowest known recruitment (% juv in fall and winter of any avian species hunted in North America. Long-term recruitment data provide insight into a population's productivity, ability to support harvest, and responses to management programs. During 1972-92, we annually collected age ratio (n = 191,968) and brood size (n = 12,239) data for greater sandhill cranes (G. c. tabida [greaters]) of the Rocky Mountain Population (RMP) at their migration stopover in the San Luis Valley, Colorado (fall), and at sites in New Mexico (winter) and southeastern Arizona (winter). We collected similar data (1987-92) for lesser sandhill cranes (G. c. canadensis [lessers]) from the Midcontinent Population (MCP) wintering in flocks mixed with RMP cranes, and for greaters of the Lower Colorado River Valley Population (LCRVP) wintering in western Arizona (1973-75 and 1989-92). Annual recruitment in the RMP averaged 8.1% (SE = 0.6) in fall and 8.0% (SE = 0.5) in winter over 21 years; mean brood size was 1.25 (SE = 0.02) in fall and 1.23 (SE = 0.02) in winter. In years with higher percent juveniles, more pairs fledged multiple young (P < 0.01); second and rarely third chicks in broods composed 20% of RMP recruitment. Recruitment and brood size had a downward trend (P < 0.01) over 21 years. During 1986-92, recruitment and brood size were below average (P < 0.01), apparently due to drought in breeding areas. We estimated survival rates of RMP cranes to be 0.95 during 1972-85, 0.94 during 1985-90, and 0.91 during 1990-92. Recruitment, survival estimates, and count data during 1985-92 suggest that the RMP is stable at 20,000-21,500 or declining slightly and cannot sustain increased harvest. Recruitment in MCP lessers averaged 11.2% (SE = 0.34) and mean brood size was 1.14 (SE = 0.02). Mean recruitment in LCRVP greaters was 4.8% (SE = 0.93), and mean brood size was 1.14 (SE = 0.028). Mean recruitment in most other North American crane populations was 5-14%. The whooping crane (G. americana) has the highest long-term (55 yr) recruitment (13.9%) of any North American crane population. Recruitment data alone cannot be used to estimate rate of increase and are difficult to interpret without additional demographic information. However, perennially low recruitment (≤ 5-6%) approximates the lowest documented mortality rates in any North American crane population, and should be a cause for concern, particularly in hunted populations. Management of crane populations can be improved by annually gathering data on recruitment, population size, and hunter harvest, and by obtaining survival estimates from long-term studies

Sexual Differences in Survival and Recovery Rates of Lesser Snow Geese

Estimates of sex-specific survival have rarely been documented in geese and, unless examined carefully, may be biased due to differential migration among sexes. Consequently, we tested for sexual differences in survival and recovery rates in lesser snow geese (Chen caerulescens caerulescens) based on 30,000 hunter recoveries of 230,000 banded geese from the mid-continent population between 1950 and 1988. Overall, there were few differences between the sexes. Estimated survival rates for immature male geese (S=0.36) from La Perouse Bay (LPB) were lower than those for females (S=0.40, P<0.0001), but this was due almost entirely to bias in the estimates caused by emigration of males to migration routes with lower recovery rates

Conditioning of Sandhill Cranes during Fall Migration

Body mass of adult female and male sandhill cranes (Grus canadensis) increased an average of 17 and 20%, respectively, from early September to late October on staging areas in central North Dakota and varied by year. Increases in body mass averaged 550 and 681 g among female and male G. c. canadensis, respectively, and 616 and 836 g among female and male G. c. rowani. Adult and juvenile G. c. rowani were lean at arrival, averaging 177 and 83 g of fat, respectively, and fat reserves increased to 677 and 482 g by mid-October. Fat-free dry mass increased by 12% among juveniles, reflecting substantial growth, but remained constant among adults. The importance of fall staging areas as conditioning sites for sandhill cranes, annual variation in body mass, and vulnerability of cranes to habitat loss underscore the need to monitor status of fall staging habitat in the northern plains region and to take steps to maintain suitable habitat where necessary. J. WILDL. MANAGE. 54(2):234-238 During fall migration, midcontinent populations of 3 subspecies of sandhill crane (G. c. canadensis, G. c. rowani, and G. c. tabida) stop for extended periods on traditional staging areas in the northern plains region of North America before continuing southward to wintering grounds located primarily in Texas and New Mexico (Johnson and Stewart 1973, Lewis 1977, Tacha et al. 1984). Cranes that nest in central and arctic Canada, Alaska, and eastern Siberia spend most of September and October on staging areas in eastern Alberta, Saskatchewan, Manitoba, North Dakota, South Dakota, and northwestern Minnesota (Lewis 1977, Melvin and Temple 1983). In North Dakota, subspecies composition varies by site. Cranes staging in the westcentral region (McLean County) are primarily G. c. canadensis, whereas cranes in the This content downloaded from 207.46.13.189 on Thu, 04 Aug 2016 05:14:12 UTC All use subject to http://about.jstor.org/terms J. Wildl. Manage. 54(2):1990 CRANE BODY COMPOSITION * Krapu and Johnson 235 central part (Pierce and Kidder counties) are primarily G. c. rowani (Johnson and Stewart 1973). The fall distribution of the midcontinent population of G. c. tabida is centered in northwestern Minnesota, and their distribution in North Dakota is limited primarily to a small population in Kidder County (Johnson and Stewart 1973). The subpopulations of sandhill cranes that stage in Kidder and McLean counties spend winter primarily along the Texas Gulf Coast (50,000-70,000 cranes, Tacha et al. 1984) and western Texas (450,000 cranes, Iverson et al. 1985), respectively. The significance of fall staging areas in the northern plains region as conditioning sites for the midcontinent sandhill crane population is poorly understood. The prolonged stay on these staging areas probably prepares birds physiologically for the continuation of fall migration (Melvin and Temple 1983) and possibly for winter, much as spring staging areas along the Platte and North Platte rivers physiologically prepare cranes for spring migration and reproduction (Krapu et al. 1985). However, fat levels among migrant sandhill cranes collected in Oklahoma in October 1979 were much lower than observed late in the spring staging period of the same year in Nebraska (Iverson 1981). This difference suggests, at least during some years, that cranes acquire less fat during autumn staging intervals in the Great Plains region than during spring, possibly because of less suitable foraging conditions on fall staging areas. We address (1) patterns of body mass change among adult G. c. canadensis and G. c. rowani on staging areas in North Dakota during the fall stopover and (2) the magnitude of change in body nutrient composition of G. c. rowani from early to late in the fall staging period. The North Dakota Game and Fish Department and cooperators provided measurements on hunter-shot cranes; B. A. Hanson and R. O. Woodward assisted in collecting and processing cranes, and C. R. Luna prepared the figures. D. P. Fellows gave constructive comments on an earlier draft of the manuscript.

Population and Harvest Characteristics of Sandhill Cranes in Southern Texas

In January 1984, an estimated 917 sandhill cranes (Grus canadensis) were harvested from 2:60,000 available birds during the 1st hunting season in southern Texas. About 60% of the harvest was from the Gulf Coast subpopulation of the midcontinent population; morphometric and electrophoretic analyses suggest cranes wintering west of Highway 16 in southern Texas are from the western subpopulation. J. WILDL. MANAGE. 50(1):80-83 Midcontinent sandhill cranes were hunted in 8 Central Flyway states, Arizona, Alaska, and Canada during the winter of 1983-84. Tacha et al. (1984) suggested that harvest management of midcontinent sandhill cranes should be based on 2 subpopulations: the western that winters primarily in western Texas, eastern New Mexico, and northern Mexico; and the Gulf Coast that winters in southern Texas. Information on population size (Iverson et al. 1985), migration routes (Tacha et al. 1984), and population structure and harvest characteristics (Carlisle and Tacha 1983; Tacha and Vohs 1984; Tacha et al. 1984, 1985a) has been obtained at major harvest locations of the western subpopulation. Little is known about site-specific population and harvest characteristics of the Gulf Coast subpopulation (Guthery and Lewis 1979, Melvin and Temple 1983). Precise population and harvest information is required for each concentration area where hunting occurs because cranes exhibit delayed breeding and low recruitment rates that could lead to overharvest of some subpopulations (Lewis 1977, Melvin and Temple 1983, Tacha et al. 1985a). The 1st hunting season for sandhill cranes in southern Texas was initiated in Zone C (Fig. 1) during January 1984. In response to concern about potential overharvest, our study documents population and harvest characteristics of the Gulf Coast subpopulation in southern Texas. This study was funded by the Tex. Parks and Wildl. Dep. (TPWD) and the Okla. Coop. Wildl. Res. Unit (OCWRU). We thank W. D. Klimstra, 0. E. Maughan, and H. W. Miller for manuscript review; personnel of the TPWD and the national wildlife refuges in southern Texas for assistance in collecting data; and the Texas landowners who permitted access to their property. The OCWRU has the Okla. Dep. Conserv., Okla. State Univ., U.S. Fish and Wildl. Serv., and Wildl. Manage. Inst. cooperating.

Habitat Use by Sandhill Cranes Wintering in Western Texas

About 80-90% of the 400,000+ mid-continent population of sandhill cranes (Grus canadensis) winter on the High Plains of western Texas. Habitat use by cranes wintering in the Rich Lake area was studied during January and February, 1979 and 1980. At least 150,000 cranes roosted on Rich Lake, and additional birds roosted on other pluvial lakes in the region. Percentage availability of each habitat type surrounding Rich Lake was compared to relative use by cranes, either by following radio-marked cranes or by systematic ground transects. Waste grain in harvested milo fields was the primary food. Milo stubble and playa lake habitats were used by cranes in greater (P < 0.05) and cotton stubble and native mesquite grasslands in lesser (P < 0.05) proportion than percentage availability. Hectares of milo stubble were 60% greater in 1979 than 1980, but the amount of waste grain in fields was three times greater in 1980. Fields disked or plowed prior to late February reduced the food base for wintering cranes. Pluvial lakes served as night roosts, and most drinking water was obtained from freshwater springs bordering the lakes. Daily mean distance cranes flew from Rich Lake was 10.8 km in 1979 and 7.8 km in 1980. Crane density, habitat availability, and mean daily distances flown from Rich Lake differed between 1979 and 1980. J. WILDL. MANAGE. 49(4):1074-1083 The western Texas High Plains have provided the principal winter habitat for sandhill cranes from mid-continental North America (Buller 1979) since at least the 1840's (Bailey 1928, Kendall 1929). From 320,000 to 440,000 cranes (80-90% of the mid-continent population) wintered in western Texas during this study (Iverson et al. 1985). Arrival began in late October; departures occurred in late February (Lewis 1977). Aggregations numbering to 200,000 birds concentrated in a few locations on the High Plains. Presence of the large concentrations was attributed to the limited availability of three essential resources in this semi-arid region: pluvial lakes for roost sites, fresh water for drinking, and waste milo grain in stubble fields (Iverson et al. 1985). The quality of winter habitat is important because cranes refuge in large numbers; depend on limited resources in the region; and are vulnerable to disturbance, water and cropland management practices, and habitat alteration. To describe and evaluate winter habitat use as a major element of the sandhill crane survival strategy, we quantified population evels, food availability, daily and seasonal habitat use, and daily and seasonal activity patterns of cranes wintering in western Texas. These parameters, coupled with quantification of physiological condition (Iverson 1981), provide data essential to management of the wintering population. This project was funded by Contract 14-180008-2133, Accelerated Res. Program for Migratory Shore and Upland Game Birds, administered by the Cent. Manage. Unit Tech. Comm. and the Migratory Bird and Habitat Res. Lab., U.S. Fish and Wildl. Serv. The Oklahoma Coop. Wildl. Res. Unit has Oklahoma State Univ., Okla. Dep. of Wildl. Conserv., U.S. Fish and Wildl. Serv., and The Wildl. Manage. Inst. cooperating.

Fat Deposition and Usage by Arctic-Nesting Sandhill Cranes during Spring

Fat Deposition and Usage by Arctic-Nesting Sandhill Cranes during Spring

Habitat Use by Migrant Sandhill Cranes in Nebraska

The principal spring staging areas of the midcontinent population of sandhill cranes (Grus can- adensis) are along the Platte and North Platte rivers in south-central Nebraska. Most of these lands are privately owned and managed for corn and cattle production. Diurnal habitat use by radio-tagged cranes was primarily in cropland (55%), native grassland (28%), and tame hayland (15%). Ninety-nine percent of the cropland use was in cornfields; 55% as grazed stubble, 36% as disced, cultivated, and plowed stubble, 7% as ungrazed stubble, and 1% unclassified. Grazed pastures accounted for 93% of the grassland locations and mowed alfalfa fields 77% of the tame hayland locations. Other habitats were seldom used. Time budget analyses indicated that cranes, while in croplands, grasslands, and haylands, spent 35, 36, and 50% of the time foraging, respectively Cranes roosted in the shallows and on nearby sandbars of about 111 km of river channel. Cranes usuallv roosted where the channel was at least 150 m wide and avoided stretches narrower than 50 m. Height of woody vegetation along shorelines and on islands influenced where cranes roosted when unobstructed channel width was less than 150 m; bridges or roads adjacent to the channel also reduced use by about half. Management recommendations are made for maintaining suitable habitat for sandhill cranes on their staging areas in Nebraska. J. WILDL. MANAGE. 48(2):407-4 17 Approximately one-half million sand- hill cranes (four-fifths of the continental population) gather annually along the Platte and North Platte rivers in Nebraska during March and early April while en route to their breeding grounds in central and arctic Canada, Alaska, and Siberia (US. Fish and Wildl. Serv., unpubl. data). Water developments in the upper Platte River Basin during this century have dras- tically reduced flows, causing major changes in channel width in the Big Bend reach (Williams 1978) where most of the cranes gather. Extensive encroachment by woody vegetation has accompanied chan- nel shrinkage (Currier 1982), and pro- posed developments would cause addi- tional habitat degradation and loss (Krapu et al. 1982), raising concern for the well-