Neal D. Niemuth

Area Sensitivity in North American Grassland Birds: Patterns and Processes

Grassland birds have declined more than other bird groups in North America in the past 35–40 years (Vickery and Herkert 2001, Sauer et al. 2008), prompting a wide variety of research aimed at understanding these declines, as well as conservation programs trying to reverse the declines (Askins et al. 2007). Area sensitivity, whereby the pattern of a species’ occurrence and density increases with patch area (Robbins et al. 1989), has been invoked as an important issue in grassland-bird conservation, and understanding the processes that drive area sensitivity in grassland birds is a major conservation need (Vickery and Herkert 2001). Here, we review the literature on North American grassland bird species that is relevant to the following questions. (1) What is the

Win-Win for Wind and Wildlife: a Vision to Facilitate Sustainable Development

Wind energy offers the potential to reduce carbon emissions while increasing energy independence and bolstering economic development. However, wind energy has a larger land footprint per Gigawatt (GW) than most other forms of energy production, making appropriate siting and mitigation particularly important. Species that require large unfragmented habitats and those known to avoid vertical structures are particularly at risk from wind development. Developing energy on disturbed lands rather than placing new developments within large and intact habitats would reduce cumulative impacts to wildlife. The U.S. Department of Energy estimates that it will take 241 GW of terrestrial based wind development on approximately 5 million hectares to reach 20% electricity production for the U.S. by 2030. We estimate there are ∼7,700 GW of potential wind energy available across the U.S., with ∼3,500 GW on disturbed lands. In addition, a disturbance-focused development strategy would avert the development of ∼2.3 million hectares of undisturbed lands while generating the same amount of energy as development based solely on maximizing wind potential. Wind subsidies targeted at favoring low-impact developments and creating avoidance and mitigation requirements that raise the costs for projects impacting sensitive lands could improve public value for both wind energy and biodiversity conservation.

Spatial and Temporal Variation in Wet Area of Wetlands in the Prairie Pothole Region of North Dakota and South Dakota

Because of their sensitivity to temperature and precipitation, wetlands in the Prairie Pothole Region (PPR) are predicted to undergo changes in number, wet area, and hydroperiod as a result of climate change. However, existing PPR wetland monitoring programs are insufficient to accurately describe broad-scale variation in hydrology that might obscure signals of climate change. We assessed spatial and temporal patterns in wet area of ~40,000 wetland basins sampled each May from 1988–2007 in the U.S. PPR. The percentage of basins containing water, the wet area of basins relative to a baseline, the coefficient of variation of wet area of basins, and correlations of wet area values with values from previous years all varied temporally, spatially, and among water regimes that characterized annual duration of surface inundation. High variability in wetness suggests that monitoring programs designed to detect changes in PPR wetlands due to climate change must be implemented over broad spatiotemporal scales and consider natural and anthropogenic factors that influence water levels to be able to distinguish directional change from natural variation. Ancillary information such as annual indices of water conditions can greatly enhance the value of wetland classification schemes such as that used in the National Wetlands Inventory.

Response of Waterbirds to Number of Wetlands in the Prairie Pothole Region of North Dakota, U.S.A.

Abstract We examined the relationship between number of wetlands and occurrence of five waterbird and one waterfowl species in the Prairie Pothole Region of North Dakota, USA, from 1980-2000. Data from 13 Breeding Bird Survey routes provided an index to regional density and distribution of Pied-billed Grebe (Podilymbus podiceps), Black Tern (Chlidonias niger), American Bittern (Botaurus lentiginosus), Northern Pintail (Anas acuta), Sora (Porzana carolina), and American Coot (Fulica americana), while 69 segments from annual Waterfowl Breeding Ground Population and Habitat Surveys provided an index to regional wetland availability. Numbers of wetlands and birds varied among years, and density and distribution of all six species showed a strong positive correlation with number of wetlands. Correlations were weaker when the number of wetlands was lagged one year, suggesting that waterbird distributions shift in response to water availability rather than respond locally. Spatial and temporal variation of waterbird habitat and numbers should be considered in monitoring and management of waterbirds in the Prairie Pothole Region.

A sampling design framework for monitoring secretive marshbirds

Abstract. A framework for a sampling plan for monitoring marshbird populations in the contiguous 48 states is proposed here. The sampling universe is the breeding habitat (i.e. wetlands) potentially used by marshbirds. Selection protocols would be implemented within each of large geographical strata, such as Bird Conservation Regions. Site selection will be done using a two-stage cluster sample. Primary sampling units (PSUs) would be land areas, such as legal townships, and would be selected by a procedure such as systematic sampling. Secondary sampling units (SSUs) will be wetlands or portions of wetlands in the PSUs. SSUs will be selected by a randomized spatially balanced procedure. For analysis, the use of a variety of methods as a means of increasing confidence in conclusions that may be reached is encouraged. Additional effort will be required to work out details and implement the plan.

USE OF WETLANDS BY SPRING-MIGRANT SHOREBIRDS IN AGRICULTURAL LANDSCAPES OF NORTH DAKOTA'S DRIFT PRAIRIE

Small, isolated wetlands in the Prairie Pothole Region of North America may be of critical importance to migrating shorebirds but are at high risk of drainage for agricultural production. We evaluated shorebird use of 1,181 temporary and seasonal wetlands within agricultural fields in the Drift Prairie physiographic region of North Dakota, USA over a 10-week period in spring of 2001. A total of 4,050 shorebirds of 25 species was observed on sampled wetlands. Shorebirds selected temporary wetlands that had water present during multiple visits, little emergent vegetation, large perimeters, and other wetlands in the surrounding landscape. Shorebirds were less likely to use wetlands showing evidence of drainage. Observed use of wetland basins suggests that small wetlands in the Prairie Pothole Region host millions of migrant shorebirds each spring. Continued existence of many of these wetlands may be threatened by a recent U.S. Supreme Court ruling that removed federal protection from certain isolated wetlands. Our results show the importance of current wetland protection provisions such as “Swampbuster” and other conservation practices of the United States Department of Agriculture Farm Program.

Effects of Lake Characteristics and Human Disturbance on the Presence of Piscivorous Birds in Northern Wisconsin, USA

Abstract Despite current anthropogenic alterations to riparian areas and littoral zones of lakes, little information is available on how human-induced alterations affect lacustrine habitat use by many piscivorous birds in northern Wisconsin, USA. The influence of lake characteristics and human disturbance on species richness and the presence of seven species of piscivorous birds was determined on 98 lakes located primarily in Vilas and Oneida counties, Wisconsin. Lakes were surveyed for species presence using shoreline perimeter surveys with total searching time standardized to two, one-hour surveys per lake. Piscivorous bird species richness was highest on large lakes with high pH levels. Using logistic regression, many species were found to be present on lakes possessing characteristics associated with high abundances of fish, including lake surface area, pH, and water clarity. At least one of these variables was included in the final models for species richness and presence of the Common Merganser (Mergus merganser), Bald Eagle (Haliaeetus leucocephalus), Great Blue Heron (Ardea herodias), and Ring-billed Gull (Larus delawarensis). Three species avoided lakes possessing characteristics associated with high levels of human disturbance; the Osprey (Pandion haliaetus) was not found on lakes with low percentages of macrophytes, the Common Merganser was absent on lakes with low water clarity, and the Common Loon (Gavia immer) was not present on lakes with many cottages. Many species of piscivorous birds were widespread regardless of the degree of human development, indicating that habituation to humans may have occurred. In addition, density-dependent factors may have precluded identification of optimal lake characteristics for some species due to habitat saturation.

Land use and vegetation associated with Greater Prairie-chicken leks in an agricultural landscape

Greater prairie-chickens (Tympanuchus cupido pinnatus) have declined dramatically across their range because of habitat loss, primarily agricultural development. In Wisconsin, most prairie-chicken populations are found in grassland reserves managed primarily for prairie-chickens. However, a few remnant populations persist in an agricultural landscape with little or no management for prairie-chickens. I compared land nse within 2.4 km of 29 prairie-chicken leks and 25 random points in an agricultural landscape to determine habitat associated with presence of prairie-chickens in central Wisconsin. Areas around leks had higher proportious of grasslands, wetlands, and shrubs than around random points, and lower proportions of forests, row crops, and hay fields. Differences between leks and random points varied with scale of sampling. Leks were unevenly distributed in the landscape, with mean distance to nearest lek shorter for leks than random points (P < 0.001). Leks were positively correlated with proportion of grass, shrub, and pasture, and negatively correlated with distance to nearest lek. Number of displaying males was negatively correlated with proportion of row crops and positively correlated with proportion of grassland in the landscape. Correlates of number of males also varied with scale of sampling.

Influence of Moisture on Density and Distribution of Grassland Birds in North Dakota

Abstract High annual variation in grassland bird populations in the Great Plains has often been attributed to changes in moisture levels, but most previous assessments of variation in grassland bird numbers have been of short duration, have occurred during a limited range of moisture levels, have been limited in geographic scope, have considered few species, or have sampled only one or few habitat types. Data from the long-term North American Breeding Bird Survey have the potential to overcome some of these shortcomings. We used linear models and information-theoretic methods to examine associations between moisture levels and populations of 17 species of grassland passerine and two species of wetland passerine in northern North Dakota from 1980 to 2004. We used data from 13 Breeding Bird Survey routes to provide indices of bird abundance and regional dispersion; we used numbers of ponds containing water identified on annual May waterfowl surveys and the Palmer Drought Severity Index (PDSI) as regional moisture indices. Responses varied among species, but the data indicated substantial support for moisture influencing the abundance of 17 of the 19 species we considered. Models including same-year pond numbers generally received more support than models including PDSI data. Dispersion of seven species throughout the study area was influenced by moisture levels, although the response was not as universal and support was not as strong as it was with abundance. Associations between grassland birds and moisture levels suggest the value of regional moisture indices to interpreting studies and surveys of grassland birds in the northern Great Plains.

Representation of Landcover Along Breeding Bird Survey Routes in the Northern Plains

Abstract The North American Breeding Bird Survey (BBS) is used extensively to make inferences about populations of many North American bird species and is increasingly being used for avian conservation planning. How well BBS routes represent the landscape is poorly known, even though accuracy of representation could significantly affect inferences made from BBS data. We used digital landcover data to examine how well landcover within 400-m buffers around BBS routes represented the surrounding landscape (the route neighborhood) for 52 routes in the Prairie Pothole Region of North Dakota and South Dakota. Differences in composition between landcover along BBS routes and the route neighborhood were not statistically significant for upland cover classes. The area of temporary and seasonal wetland basins was accurately represented by BBS routes in our study area, but the area of semipermanent and permanent wetland basins was significantly underrepresented along BBS routes. Number of wetland basins and upland patches was higher along routes. Area of urban, forest, and hay landcover classes was higher along routes, although differences were not statistically significant. Amount of bias in landcover representation was negatively correlated with the proportion of each landcover type in the study area, but bias was not correlated with area of the route neighborhoods. Differences between landcover along BBS routes and the route neighborhood were primarily attributable to increased anthropogenic activity along roads and siting of roads away from relatively large, deep water bodies. Our results suggest that inferences made from BBS data in our study region are likely biased for species that are associated with deeper-water habitats or are strongly influenced by landscape fragmentation. Inferences made from BBS data for species associated with uplands or shallow wetlands are less likely to be biased because of differences in landcover composition.