Missouri Coteau Research Articles

Reassessing perennial cover as a driver of duck nest survival in the Prairie Pothole Region

AbstractConservation plans designed to sustain North American duck populations prominently feature a key hypothesis stating that the amount of the landscape in perennial cover surrounding upland duck nests positively influences nest survival rates. Recent conflicting research testing this hypothesis creates ambiguity regarding which management actions to pursue and where to prioritize conservation delivery. We compared existing models and new formulations of existing models explaining spatiotemporal variation in nest survival using independent data documenting the fate of >20,000 duck nests within the Drift Prairie, Missouri Coteau, and Prairie Coteau physiographic regions of the United States Prairie Pothole Region during 2002–2018. Our results suggest an inconsistent relationship between perennial cover and survival of upland duck nests, which depended upon physiographic region and current and time‐lagged landscape and environmental conditions. The magnitude and direction of how perennial cover correlated with daily nest survival depended on its dominance as a landcover type. A positive relationship existed when perennial cover was a minor component of landcover in all physiographic regions (<30% of a 10.4‐km2 area) and, in the Drift Prairie and Prairie Coteau, when perennial cover was the dominant landcover type (>60%). A constant or negative relationship was predicted at locations of about 30–60% perennial cover. Additionally, environmental conditions (i.e., density of wetlands and estimated gross primary productivity in the previous year) moderated or enhanced the effect of perennial cover on nest survival, depending on physiographic region. Our finding of inconsistency in the relationship between perennial cover and nest survival contradicts the conservation premise that nest survival universally increases linearly when uplands are converted to perennial cover. Promoting policies and management actions designed to increase perennial cover can be expected to be situationally but not consistently associated with higher survival of upland duck nests.

The Excavation of a Stone Cairn Cache in Southern Saskatchewan

In 2018, a stone cairn was discovered on a prominent hilltop in the Missouri Coteau in southern Saskatchewan, not an uncommon discovery. Due to potential impacts from development, a salvage excavation commenced which included the excavation of the entire stone cairn structure and additional subsurface testing in the immediate area. A preliminary interpretation for the stone cairn was its functional use as a navigational marker; however, the initial interpretation was retracted upon the discovery of a cache cavity within the unexpectedly large structure of the stone cairn. Had the excavation not occurred, the stone cairn may have been misinterpreted; this is a common issue at stone cairn sites across the northern Plains.

Simulating the effects of climate variability on waterbodies and wetland‐dependent birds in the Prairie Pothole Region

AbstractUnderstanding how bird populations respond to changes in waterbody availability in the climatically variable Prairie Pothole Region (PPR) of North America hinges on being able to couple hydrological and climate modeling to represent potential future landscapes. Model experiments run with the Pothole Complex Hydrologic Model using downscaled climate data (variables relating to precipitation, temperature, and potential evapotranspiration at 1/8° spatial resolution under four general circulation climate models and two gas emissions scenarios) were used to forecast the abundances of six focal wetland‐dependent bird species in the Missouri Coteau portion of the PPR, providing ensemble scenarios at a spatial scale relevant to resource management. Although the projected number of May ponds (waterbodies present during bird breeding season) fluctuated through time with some decadal periodicity (and with the number present in a given year reflecting abundance over the previous three years), the ensemble model average indicated an increase in the average number of waterbodies present by the turn of the next century. Overall, the model experiments conservatively projected an 11.75% increase in the number of waterbodies present by 2090–2099 compared to a baseline period from 1967 to 2005 in the PPR. Wetland‐dependent bird occurrence and abundance were significantly associated with temporal patterns and decadal periodicity in waterbody dynamics. Because of the strong associations between wetland‐dependent bird occurrence and abundance and the number of prairie potholes, projected waterbody increases are forecasted to result in an 11.97% overall increase in occurrence and 8.63% increase in abundance of the six focal species by the end of the 21st century; these results contrast with forecasted drought‐associated declines in waterbodies and birds in the PPR. This integrated hydrological–climatological approach offers a means of assessing how wetland‐dependent bird populations may respond to changes in wetland habitat availability due to a changing climate. Our results provide information that can help managers decide how to mitigate the effects of climate shifts on the distribution of wetland habitat and biota.

Comparing tiers of a multi-tiered wetland assessment in the Prairie Pothole Region

Wetland assessment has been shown to be an important tool in understanding the condition and function of the world’s wetlands, and use of muli-tiered assessment strategy has been recommended. In order to evaluate the performance of each tier of a multi-tiered wetland assessment strategy, we sampled 255 seasonally-ponded wetlands in the Missouri Coteau, the most wetland dense ecoregion in the Prairie Pothole Region. We assessed the condition of each study wetland using four sampling methods and models (tiers) of increasing levels of effort and complexity: (1) a level 1 assessment using the geographic information system-based Landscape Wetland Condition Analysis Model (LWCAM); (2) a level 2 assessment using the North Dakota Rapid Assessment Method (NDRAM); (3) a level 3- assessment using the vegetative-based Floristic Quality Index (FQI) and (4) a level 3 assessment consisting of a Hydrogeomorphic (HGM) Model functional assessment. We compared assessment tiers to determine how similar the different levels of assessment ranked sites either by condition or function. Both the NDRAM and FQI assessments, though very different in wetland characteristics assessed, provided similar condition rankings as the more intensive level 3 HGM assessment (89 and 90% similar, respectively). Additionally, the FQI was 86% similar to the level 2 NDRAM, indicating that these two assessment methods have utility in assessing wetlands similar to a HGM assessment. Information from this study can be used as a tool for determining need specific, financial, and time appropriate wetland sampling methods.

Effect of wind energy development on breeding duck densities in the Prairie Pothole Region

AbstractIndustrial wind energy production is a relatively new phenomenon in the Prairie Pothole Region and given the predicted future development, it has the potential to affect large land areas. The effects of wind energy development on breeding duck pair use of wetlands in proximity to wind turbines were unknown. During springs 2008–2010, we conducted surveys of breeding duck pairs for 5 species of dabbling ducks in 2 wind energy production sites (wind) and 2 paired reference sites (reference) without wind energy development located in the Missouri Coteau of North Dakota and South Dakota, USA. We conducted 10,338 wetland visits and observed 15,760 breeding duck pairs. Estimated densities of duck pairs on wetlands in wind sites were lower for 26 of 30 site, species, and year combinations and of these 16 had 95% credible intervals that did not overlap zero and resulted in a 4–56% reduction in breeding pairs. The negative median displacement observed in this study (21%) may influence the prioritization of grassland and wetland resources for conservation when existing decision support tools based on breeding‐pair density are used. However, for the 2 wind study sites, priority was not reduced. We were unable to directly assess the potential for cumulative impacts and recommend long‐term, large‐scale waterfowl studies to reduce the uncertainty related to effects of broad‐scale wind energy development on both abundance and demographic rates of breeding duck populations. In addition, continued dialogue between waterfowl conservation groups and wind energy developers is necessary to develop conservation strategies to mitigate potential negative effects of wind energy development on duck populations. Published 2012. This article is a U.S. Government work and is in the public domain in the USA.

Climate‐driven variability in lake and wetland distribution across the Prairie Pothole Region: From modern observations to long‐term reconstructions with space‐for‐time substitution

This study was designed (1) to explore the links between climate variability and the population dynamics of closed‐basin surface water bodies of the Prairie Pothole Region (PPR) in North America, and (2) to test the validity of space‐for‐time (SFT) substitution approach for the analysis of hydrologic systems. Observational results from 1981 to 2000 show that the climate with respect to annual residual moisture (ε, i.e., precipitation minus potential evaporation or evapotranspiration) of the PPR changed across space (over 0.6 m) and time (over 0.3 m in central North Dakota), causing spatiotemporal variability in water areas and water body numbers. Spatial analysis of a suite of surface water complexes along a spatial ε gradient in the Missouri Coteau shows that a four parameter Boltzmann function quantitatively describes how the number of water bodies (N) varied as a function of 5‐year average annualε (R2 = 0.76). Temporal analysis of monthly N data (1931–2005) reconstructed by a hydrologic model also demonstrates that values of temporally varying N were highly correlated with εand yielded a nearly identical Boltzmann function. This result confirms the validity of SFT substitution and suggests that detailed modern spatial data can be used to interpret hydrologic system behaviors under past or future climate conditions. This study also has important regional‐scale implications for water resources management by providing a complete picture of the spatiotemporal water body distribution across the entire PPR and the potential for rapidly converting climate predictions into surface water assessments.

Predicting Risk of Habitat Conversion in Native Temperate Grasslands

Native grasslands that support diverse populations of birds are being converted to cropland at an increasing rate in the Prairie Pothole Region of North America. Although limited funding is currently available to mitigate losses, accurate predictions of probability of conversion would increase the efficiency of conservation measures. We studied conversion of native grassland to cropland in the Missouri Coteau region of North and South Dakota (U.S.A.) during 1989-2003. We estimated the probability of conversion of native grassland to cropland with satellite imagery and logistic regression models that predicted risk of conversion and by comparing the overlap between areas of high biological value and areas most vulnerable to conversion. Annualized probability of conversion was 0.004, and 36,540 ha of native grassland were converted to cropland during the period of our study. Our predictive models fit the data and correctly predicted 70% of observed conversions of grassland. Probability of conversion varied spatially and was correlated with landscape features like amount of surrounding grassland, slope, and soil productivity. Tracts of high biological value were not always at high risk of conversion. We concluded the most biologically valuable areas that are most vulnerable to conversion should be prioritized for conservation. This approach can be applied broadly to other systems and offers great utility for implementing conservation in areas with spatially variable biological value and probability of conversion.

Soil organic carbon changes and distribution in cultivated and restored grassland soils in Saskatchewan

The impacts of grassland restoration on amounts, forms and distribution of soil organic carbon (SOC) were examined in paired cultivated and restored grassland catenae of the Missouri Coteau region in south-central Saskatchewan, Canada. Total SOC (0–15 cm depth) and light fraction organic carbon (LFOC) (0–7.5 cm) contents were determined in paired catenae in upland areas, and in the surface (0–15 cm) and at depth (>15 cm) in the wetland fringe areas. Mass of SOC was higher in the restored grassland catenae than in the cultivated equivalents. In both the cultivated and restored grassland catenae at the three sites, footslope positions consistently had a higher mass of SOC. However, the shoulder positions showed the greatest response in soil C sequestration to grass seed-down, with a 1.4–2.9 Mg ha−1 year−1 SOC increase apparent over an approximately eight-year period. The mass of LFOC and the proportion of SOC comprised of LFOC was also higher in the restored grassland, reflective of higher recent C inputs. Rates of C sequestration in the Missouri Coteau based on SOC differences in the paired comparisons were estimated to be 0.3–2.9 Mg C ha−1 year−1, depending upon site and slope position. In the wetland fringe region of the landscape, the three sites also had higher surface or subsurface SOC in the grassland restoration. In general, SOC changes at depth (below 15 cm) in the restored grasslands appeared to be less consistent than changes in SOC in the surface 0–15 cm soil. In conclusion, the findings suggest that a switch to permanent cover on these soils will significantly increase C sequestered in the soil.

Tracking palustrine water seasonal and annual variability in agricultural wetland landscapes using Landsat from 1997 to 2005

AbstractWetlands densely populate the ecoregion transecting the center of the Prairie Pothole Region (PPR) known as the Missouri Coteau and epicenter to the most productive waterfowl‐breeding habitat in North America. These palustrine, depressional basin waters vacillate with regional drought and deluge, so surface water fluctuations over time modulate wetland productivity, habitat, and water quality functions. Models predict formidable effects of climate change on glacial basin surface waters, yet large‐scale, long‐term observation data are lacking to compare against predicted changes. Current, optical‐based water detection models do not delineate marsh vegetation from shallow, turbid, high‐chlorophyll waters common to the region. We developed a palustrine wetland spectral model for tracking open surface waters using Landsat imagery, which we evaluated for a 2500 km2 landscape that estimates seasonal and annual open water variability for thousands of individual wetlands in the Missouri Coteau ecoregion. Detection accuracy of 96% was achieved for water bodies greater than a half‐pixel in size. We identified shifts in the distribution of water permanence classes within and between years for waters emerging in spring, mid‐summer, and late summer from 1997 to 2005 and identified a maximum of 19 047 basins with open water (12% of the landscape) populating 2500 km2. For the 2005 growing season, we observed only 8757 basins with open water (6% of the landscape) for the same area. Declines were greatest for water bodies detected only in spring, suggesting a loss of those wetlands functioning to recharge groundwater stores early in the season and a high sensitivity to observed reductions in snowfall. If landscape factors driving open water coverage and wetland density are similar for the entire Missouri Coteau, we estimate the number of basins containing at least a pixel of water for this region declined from 577 600 to 266 000 between 1997 and 2005.

Mapping Prairie Pothole Communities with Multitemporal Ikonos Satellite Imagery

We evaluated the ability of Ikonos imagery from August and October 2000 to classify prairie pothole community types of the Missouri Coteau of North Dakota. Classification tree analyses were conducted to create land-cover maps at three levels of detail. The analyses successfully distinguished broad cover types (potholes including emergent vegetation versus upland vegetation) at 92 percent overall accuracy. Overall accuracy dropped to 80 percent when upland vegetation was segregated into woody and grassy communities and to 71 percent when we attempted to classify at the species or near-species levels. The use of two image dates was of importance in the classifications; the failure to acquire early season imagery, therefore, might have impaired our results.

Remote wetland assessment for Missouri Coteau prairie glacial basins

Missouri Coteau prairie glacial wetlands are subject to numerous anthropogenic disturbances, such as cultivation, construction, and chemical inputs from upland land-use practices. High wetland density and temporal variability among these ecosystems necessitate synoptic tools for watershed-scale wetlands assessment and comprehensive monitoring. We developed a Geographic Information Systems (GIS) classification model for Missouri Coteau prairie glacial wetlands in North Dakota, USA and derived two indices that provide data salient to landscape-scale wetland assessment and monitoring. One, the Basin Buffer Index (BBI), delineates areas of natural vegetation that buffer waters from anthropogenic disturbance. The second, the Hydric Vegetation Index (HVI), delineates areas of hydric vegetation communities essential to prairie glacial wetland function. The model was developed by spectrally characterizing structural attributes common to glacial basins, such as hydroperiod, canopy architecture, and plant life-form and evaluating the potential for spectral detection of the natural vegetation buffers that surround these wetlands. Spectral separation among community zones in the green, red, and mid-infrared regions were evident in hyperspectral data and were convolved to fit multi-spectral satellite sensors. Model application using Landsat ETM+ and SPOT 5 satellite data over the central North Dakota study area produced classifications for buffer delineation and hydric community detection with 89 and 85% accuracy, respectively. By integrating remote sensing technology with those structural factors fundamental to wetland quality (i.e., land-use and natural vegetation buffers surrounding water bodies), we illustrate a method for evaluating wetland condition at a landscape scale.

A Swainson's hawk staging area long the Missouri Coteau in southeast Saskatchewan

A Swainson's hawk staging area long the Missouri Coteau in southeast Saskatchewan

A fossil record of colonization and response of lacustrine fish populations to climate change

To study fish species colonization and the response of populations to climate change, we reexamined a well-preserved late Pleistocene to early Holocene fossil fish assemblage from lake deposits on the Missouri Coteau, North Dakota. The fossil fishes in the assemblage include complete specimens of yellow perch (Perca flavescens), brassy minnow (Hybognathus hankinsoni), blacknose shiner (Notropis heterolepis), banded killifish (Fundulus diaphanus), and brook stickleback (Culaea inconstans). The sequence of colonization is explained by individual thermal and relative water velocity tolerances for each species. There are six peaks in fish abundance during approximately 1000 years, indicating a response to environmental perturbations. Charcoal deposition from fires is inferred to represent episodic droughts during which nutrient levels were reduced and fish abundance declined. The fluctuations follow an overall trend of increased fish abundance during a time when lake-marginal vegetation changed from a spruce to a deciduous forest in response to climatic warming. This study provides insight into the complex effects of a changing climate on fish populations and demonstrates the potential of using fossils to examine the long-term abundance patterns of contemporary fish species.

Invertebrate egg banks of restored, natural, and drained wetlands in the prairie pothole region of the United States

Analogous to ‘seed banks,’ ‘egg banks’ are important for seasonal succession and maintenance of invertebrate species diversity throughout wet and dry cycles in the prairie pothole region. Further, recruitment of invertebrates from relic egg banks in the sediments and dispersal of eggs into wetlands is believed to be important for reestablishment of invertebrates in recently restored wetlands. Although tens-of-thousands of wetlands have been restored in the prairie pothole region of the United States, studies have not been conducted to evaluate the recovery of invertebrate egg banks in restored wetlands. We used taxon richness and abundance as indicators of potential egg bank recovery and compared these parameters in restored wetlands to those of non-drained and drained wetlands with a history of cultivation and also to reference wetlands with no history of cultivation. We found few significant differences among wetland categories within three physiographic regions (Glaciated Plains, Missouri Coteau, and Prairie Coteau). Most statistical comparisons indicated that restored wetlands had invertebrate egg banks similar to reference, nondrained, and drained wetlands. The one exception was drained seasonal wetlands in the Glaciated Plains, which had significantly lower taxon richness and invertebrate abundance than the other wetland categories. Trends did suggest that invertebrate egg bank taxon richness and abundance are increasing in restored seasonal wetlands relative to their drained analogues, whereas a similar trend was not observed for restored semi-permanent wetlands. Although recovery was not related to years since restoration, comparisons of restored wetlands with reference wetlands suggest that recovery potential may be inversely related to the extent of wetland drainage and intensive agriculture that varies spatially in the prairie pothole region. Our research suggests that periodic drawdowns of semi-permanent restored wetlands may be needed to promote production and development of invertebrate egg banks. Inoculation of restored wetlands may also be needed in areas where extensive wetland drainage has resulted in fewer wetland habitats to provide sources of passively dispersed eggs to newly restored wetlands.

The Holocene history of Oro Lake, one of the western Canada's longest continuous lacustrine records

Over the past decade, there have been significant advances in our understanding of the Holocene history of the Great Plains region of western Canada. However, despite this increased interest, paleolimnological research is limited by a paucity of study sites with relatively long, uninterrupted stratigraphic sequences. To date, only three Canadian Great Plains lakes have provided complete, uninterrupted sequences spanning the past 10,000 years. Oro Lake is one of these. Oro Lake is small, perennial, and saline. It occupies a topographically closed basin on the Missouri Coteau in southern Saskatchewan, Canada. Its 10,000-year stratigraphic sequence consists mainly of well-bedded, calcareous, and gypsiferous clayey silts. A short-lived early Holocene freshwater siliciclastic-dominated lake occupied the newly formed basin immediately after deglaciation. At ∼9300 BP, limnological conditions changed dramatically and abruptly. Since then, alkaline, high-salinity brines with high Mg/Ca ratios have prevailed. Stable meromictic conditions existed from about 9300 to ∼7400 BP, with maximum salinities (>75 ppt) occurring at 8300 BP. About 7400 years ago, gradually increasing aridity during the mid-Holocene resulted in increased eolian sedimentation, reorganization of the groundwater influx, and occasional breakdown of meromixis. About 4000 BP, the lake returned to a mainly stratified water column with subaqueous soluble salts being precipitated from the monimolimnion, and aragonite and Mg-carbonates being generated from the mixolimnion. During the most recent 1000 years, periodic hypersaline conditions became more common, coincident with decreased concentrations of Ca2+ and complimentary increased proportions of Mg2+ and Na+ ions.

Insects as indicators of land use in three ecoregions in the Prairie Pothole Region

We sampled populations of insects in the prairie pothole region of North Dakota, USA, to determine whether relationships existed between community- or taxon-level indicators and 11 land-use types. Our goal was to determine if agricultural impacts were reflected in measurable differences for insect indicators: abundance, taxa richness, and diversity. Insects were sampled with light traps at 126 wetland basins in three ecoregions. Sampling was conducted three times each year during the spring and early summer of 1995 and 1996. Sites were selected based on the proportion of cropland to grassland, hayland, and Conservation Reserve Program land surrounding wetland basins at 50 and 400 m radii. Other land-use types included in our analyses were woodland, roadways, and five wetland types: permanent, semipermanent, seasonal, temporary, and riverine. In both years, taxa richness, abundance, and diversity were greater for the second (June) and third (July) sampling periods than for the first period (May), and indicators were greater in the Drift Plain and Red River Valley ecoregions than in the Missouri Coteau ecoregion. Our analyses indicated several significant associations between insect indicators and land-use types; however, r2 values were generally low. Much more of the variance in insect measures was explained by temperature, seasonal, and ecoregion effects. Several associations were significant within individual ecoregions (i.e., abundance of aquatic insects. Caenidae, Scarabaeidae, and Lepidoptera and number of Ephemeroptera families). However, no indicators were found in common for all three ecoregions. Several significant associations with land use were identified across all sites (i.e., all ecoregions combined). A small number of the significant relationships found across all sites were related to agricultural land use, and several indicated a negative relationship with grasslands. However, we observed several positive relationships between our insect indicators and riverine wetlands across sites and in the Red River Valley ecoregion for both years and spatial scales (i.e., the abundance of Caenidae, Scarabaeidae, Ceratopogonidae, Hydropsychidae, and Hydroptilidae).

Holocone paleovegetation and paleohydrology of a prairie pothold in southern Saskatchewan, Canada

The Andrews site represents one of countless prairie potholes found in areas of hummocky moraine on the northern Great Plains. Sediments from a depth of 5.8 to 3.1 m at this 'kettle-fill' site in the Missouri Coteau upland of southern Saskatchewan, Canada, provides a record of vegetation, climate, and hydrologic changes within a small, ca 30 m diameter, closed-drainage basin from ca 10.2 to 5.8 ka. Plant macrofossil analyses of 67 samples, 6 14C ages, and stratigraphy were used to identify 5 zones, representing the paleohydrological changes that followed deglaciation in southern Saskatchewan. Results of this study indicate that with the melting of residual stagnant ice a pond (>2 m deep) with abundant aquatic, emergent, and shoreline plants developed in the basin at ca 10.2 ka and persisted until at least ca 8.8 ka. During this time there was a shift in upland vegetation from a white spruce forest (Zone II) to a deciduous parkland at ca 10 ka (Zone III). As climate warmed, brackish and alkaline conditions developed coincident with shallowing of the pond at the end of Zone III. The perennial water phase ended at ca 8.8 ka and was followed by a low-water stand lasting ca 1100 years. Prairie fires and slopewash from unstable slopes were dominant sedimentological processes until ca 7.7 ka (Zone IV). Water levels began to rise and between ca 7.7 and 5.8 ka a semi-permanent pond was established in a grassland setting (Zone V). After ca 5.8 ka this prairie pothole wetland became ephemeral, to the point that plant macrofossils could not be preserved, a situation continuing today. Interactions between climate change, variability in local groundwater supply, and sedimentological processes likely account for the paleohydrologic events reconstructed at the Andrews site.

The Dirt Hills structure: an ice-thrust feature in southern Saskatchewan, Canada

The Dirt Hills structure is expressed at the surface as a broad, arcuate moraine, 7.5 km wide, 120 m high, and 40 km long. The structure is composed mainly of bedrock and drift consisting of three slabs stacked to form a single block 215 m thick. The shear zones that bound the slabs are mainly in clays of the Bearpaw Formation. The Dirt Hills structure originated during the last deglaciation when the glacier, under compressive flow, readvanced up the Missouri Coteau escarpment and stacked the subglacial slabs of bedrock and drift. The subparallel, arcuate ice-thrust ridges are formed presumably by imbricate thrust faults originating from the uppermost shear zone.

Survival of Mallard Broods in South-Central North Dakota

Survival characteristics of 25 broods of Mallards (Anas platyrhynchos) were determined on a study area in the Missouri Coteau of south-central North Dakota in 1976-1977. Radio-equipped Mallard hens fledged at least one duckling in 7 of 16 (44%) broods produced in 1976, 5 of 9 (55%) in 1977, and 12 of 25 (48%) for both years combined. Of the 13 broods in which all young were lost, 11 (85%) were lost within the first two weeks after hatching. All losses of entire broods occurred in wetlands; few ducklings and no entire broods were lost during overland travel. Predation by mink (Mustela vison) was apparently the principal cause of duckling mortality.

Ferruginous Hawk Populations and Habitat Use in North Dakota

Ferruginous hawks (Buteo regalis) were studied in central North Dakota on a 1,259-km2 intensive study block and on a surrounding study area (16,519 km2) from 1977 to 1979. A total of 629 occupied nests was examined. Highest nest densities (0.08 nest/km2) were in the Missouri Coteau in 1979. Few nests were found on the more intensively cultivated Drift Plain. We estimated the breeding population in the study area each year using 148 sample plots (? = 440 nesting pairs). Pairs that nested on the ground selected only sites on rugged landforms in isolated areas, mostly end and dead-ice moraines. Land use within 1.0 km of nests was mostly (76.5%) pasture and haylands. About 95% of the area around ground nests was grassland. Tree and tower nesting birds appeared less sensitive to surrounding land use. Pairs on the intensive study block used a wide variety of nest sites including trees (63.6%), ground (20.9%), power line towers (8.0%), haystacks (5.4%), and rock piles, utility poles, and shrubs (2.1%). Reoccupancy rates were higher (63.7%) for tower nests than for other sites. Nest success was related to the type of nest site and was highest (86.7%) in certain power line towers. Mean number of young fledged per occupied nest was highest (2.8) for ground nests. Summer storms were a major cause of loss; tree nests were particularly vulnerable. Richardson's ground squirrels (Spermophilus richardsonii) were taken as prey most often. Ferruginous hawks are closely associated with grasslands, particularly native prairie. J. WILDL. MANAGE. 47(1): 146-157 Resource managers have identified the need to gather baseline data on raptors inhabiting portions of the Northern Great Plains subjected to disturbances from energy development (D. L. Evans, unpubl. rep., U.S. Fish and Wildl. Serv., Jamestown, N.D., 1980) and intensive agriculture (Stewart 1975). Because raptors are indicators of environmental quality (Odum 1971), knowledge of their densities and productivity can also be used to assess ecosystem condition. The ferruginous hawk is a major component of the raptor fauna in much of western North America and has been the focus of a number of recent studies (Olendorff 1973; Howard 1975; Lokemoen and Duebbert 1976; Fitzner et al. 1977; Smith and Murphy 1978; Wakeley 1978a,b; Lardy 1980; Schmutz et al. 1980; Powers 1981; Blair and Schitoskey 1982). Despite these studies, its population status is largely unknown in most areas of the breeding range (Evans 1982). Historical data and casual observations indicate the ferruginous hawk is a common breeder in central North Dakota (Stewart and Kantrud 1972, Stewart 1975). We studied the ferruginous hawk from spring 1977 through summer 1979 to evaluate density, productivity, habitat preference, nest site selection, and prey use of the species in North Dakota. We acknowledge the field assistance of B. A. Hanson, T. J. Moser, D. L. Pieske, R. N. Rosenfield, J. L. Sease, and particularly P. M. Konrad and D. L. Evans. T. Gatz provided information on some nest locations. R. Schafer, M. Edman, and pilot T. Cochran (Minnkota Power Coop., Inc., Grand Forks, N.D.) arranged for the use of a helicopter on power line surveys. D. A. Davenport and C. L. Nustad provided computer programming and A. M. Frank ' Present address: Wildlife Research Field Station, U.S. Fish and Wildlife Service, 6924 Tremont Road, Dixon, CA 95620. 146 J. Wildl. Manage. 47(1):1983 This content downloaded from 40.77.167.43 on Tue, 21 Jun 2016 05:24:41 UTC All use subject to http://about.jstor.org/terms FERRUGINOUS HAWK POPULATIONS * Gilmer and Stewart 147 and D. H. Johnson assisted with statistical design and analysis. K. Rankin, R. Nakamoto, J. Hicks, and P. N. Konrad assisted with data preparation. E. Bartels provided library services. A. B. Sargeant, R. R. Olendorff, R. P. Howard, J. W. Wiley, and A. M. Frank kindly reviewed the manuscript. W. R. Dryer provided technical editorial services. Support for this study was provided by the U.S. Fish and Wildlife Service.