Bird Population Changes Following the Establishment of a Diverse Stand of Woody Plants in a Former Crop Field in North Dakota, 1975– 2015

Changes in the coverage of trees and shrubs on the North Dakota landscape since Euro- American settlement have likely had a pronounced impact on bird species that favor woody vegetation. Long- term data sets on breeding bird populations in wooded habitats in North Dakota or in the Great Plains are scarce. In 1975 a wildlife habitat plot was established in a 10.5 ha cropland field with a long history of small- grain production. Th e objective of this article is to evaluate the successional changes in bird populations as the habitat at this site became more biologically and structurally complex aft er the establishment of a diverse stand of shrubs and trees. Between 1975 and 2015, 103 species or varieties of native and non- native trees, shrubs, or vines were planted in this wildlife habitat plot (hereaft er woodlot); 58.2% of those species were still present in 2016. Th e avian community in the woodlot increased in abundance and diversity as the woody vegetation increased in complexity and maturity, but the changes in abundance varied among ecological bird groups. Grassland bird abundance remained relatively constant but uncommon throughout the four decades aft er woody vegetation was first established. Bird species associated with shrublands and open woodlands and edges responded positively and showed the greatest increases in abundance during the 41- year period. Th e abundance of bird species associated with open areas with scattered trees or shrubs (i.e., savanna habitat) increased during the first half of the study but declined during the second half. Bird species associated with forest habitats were rare throughout the 41- year period, but their abundance increased during the most recent two decades. Results of this study are important for informing decisions about restoration efforts of riparian forests and other native wooded areas in the Great Plains and setting expectations for the time- scale required for the return of assemblages of species of woodland birds

Maps of Distribution and Abundance of Selected Species of Birds on Uncultivated Native Upland Grasslands and Shrubsteppe in the Northern Great Plains

Many areas of the northern Great Plains (Fenneman 1931) remain poorly known ornithologically. Knowledge of species distribution in portions of this vast area has been advanced by recent State birds books (Stewart 1975; South Dakota Ornithologists\u27 Union 1978) but many voids remain. Especially desirable for biologists and land managers is information concerning the relative abundance of plant and animal species over large land areas. This information can only be obtained from extensive surveys of the biota. The field of community ecology has been severely hampered by lack of information on species abundance (Dice 1930; Cain 1947; Partch 1962; Udvardy 1963). In 1974-78, the U.S. Fish and Wildlife Service\u27s Migratory Birds and Biological Services Programs jointly funded an extensive study in an attempt to develop a classification of native, northern Great Plains grasslands based on their use by breeding birds. Other goals were to investigate the effects of grazing and other environmental factors on breeding birds and the vegetation. The results of these portions of the study will be reported later. The purpose of this report is to provide ecologists and ornithologists with recent information on areas of abundance of some of the more important members of the avifauna which use grasslands. This information should also prove valuable to conservationists and resource managers as energy developments and further expansion and intensification of the agricultural industry result in increased destruction of native grassland habitat in areas now supporting some of the less common species. During the study, breeding bird censuses were conducted on 615 plots of uncultivated native upland grassland and shrubsteppe in the portion of the northern Great Plains that lies within the United States (Fig. 1). The study area (about 6 X 10 3 km 2) includes portions of Montana, Wyoming, Colorado, North Dakota, South Dakota, and Nebraska. Grasslands in the mountains, badlands, sand deposits, and river valleys (shown in white on Fig. 1) were not sampled and so are excluded from further consideration

Avian Associations of the Northern Great Plains Grasslands

The grassland region of the northern Great Plains was divided into six broad subregions by application of an avian indicator species analysis to data obtained from 582 sample plots censused during the breeding season. Common, ubiquitous species and rare species had little classificatory value and were eliminated from the data set used to derive the avian associations. Initial statistical division of the plots likely reflected structure of the dominant plant species used for nesting; later divisions probably were related to foraging or nesting cover requirements based on vegetation height or density, habitat heterogeneity, or possibly to the existence of mutually similar distributions or shared areas of greater than average abundance for certain groups of species. Knowledge of the effects of grazing, mostly by cattle, on habitat use by the breeding bird species was used to interpret the results of the indicator species analysis. Moderate grazing resulted in greater species richness in nearly all subregions; effects of grazing on total bird density were more variable

Avian Associations of the Northern Great Plains Grasslands

The grassland region of the northern Great Plains was divided into six broad subregions by application of an avian indicator species analysis to data obtained from 582 sample plots censused during the breeding season. Common, ubiquitous species and rare species had little classificatory value and were eliminated from the data set used to derive the avian associations. Initial statistical division of the plots likely reflected structure of the dominant plant species used for nesting; later divisions probably were related to foraging or nesting cover requirements based on vegetation height or density, habitat heterogeneity, or possibly to the existence of mutually similar distributions or shared areas of greater than average abundance for certain groups of species. Knowledge of the effects of grazing, mostly by cattle, on habitat use by the breeding bird species was used to interpret the results of the indicator species analysis. Moderate grazing resulted in greater species richness in nearly all subregions; effects of grazing on total bird density were more variable

Ecological Distribution of Breeding Waterfowl Populations in North Dakota

The distribution of breeding waterfowl populations on various wetland habitat types was investigated in North Dakota during 1967-69. Data were obtained by stratified random sampling techniques. The total wetland acreage in North Dakota was estimated to be about 3.2 million acres. Natural basin wetlands comprised about 77 percent of the acreage and 91 percent of the number of wetlands in the state and were utilized by about 76 percent of the state\u27s breeding duck population. Among the four biotic regions of the state, numerical and areal composition of wetlands varied considerably. Natural basin wetlands varied from a low of about 4 percent of total wetland acreage in the Southwestern Slope Region to a high of 93 percent in the Prairie Pothole Region. About 84 percent of the statewide duck population occurred in the Prairie Pothole Region. Within the Prairie Pothole Region, seasonal (Class III) ponds comprised 36 and 23 percent, respectively, of the total acreage and number of wetlands, and semipermanent (Class IV) ponds and lakes comprised 18 and 3 percent, respectively, of these totals. Agriculture has had drastic effects on the wetlands in this region as evidenced by the fact that natural basin wetlands with tilled bottom soils (chiefly Class II and Class III wetlands) comprised about 29 percent of area but 52 percent of numbers of all wet- lands. In the Prairie Pothole Region, seasonal ponds and semipermanent ponds and lakes were utilized by about 48 and 27 percent, respectively, of the total breeding ducks. Optimum environmental conditions for breeding dabbling ducks were present during years when large numbers and acreages of seasonal (Class III) pond basins contained surface water. Semipermanent (Class IV) ponds and lakes were the principal habitats for breeding diving ducks, and were also important to dabbling ducks, particularly during dry years

Bird Population Changes Following the Establishment of a Diverse Stand of Woody Plants in a Former Crop Field in North Dakota, 1975– 2015

Changes in the coverage of trees and shrubs on the North Dakota landscape since Euro- American settlement have likely had a pronounced impact on bird species that favor woody vegetation. Long- term data sets on breeding bird populations in wooded habitats in North Dakota or in the Great Plains are scarce. In 1975 a wildlife habitat plot was established in a 10.5 ha cropland field with a long history of small- grain production. Th e objective of this article is to evaluate the successional changes in bird populations as the habitat at this site became more biologically and structurally complex aft er the establishment of a diverse stand of shrubs and trees. Between 1975 and 2015, 103 species or varieties of native and non- native trees, shrubs, or vines were planted in this wildlife habitat plot (hereaft er woodlot); 58.2% of those species were still present in 2016. Th e avian community in the woodlot increased in abundance and diversity as the woody vegetation increased in complexity and maturity, but the changes in abundance varied among ecological bird groups. Grassland bird abundance remained relatively constant but uncommon throughout the four decades aft er woody vegetation was first established. Bird species associated with shrublands and open woodlands and edges responded positively and showed the greatest increases in abundance during the 41- year period. Th e abundance of bird species associated with open areas with scattered trees or shrubs (i.e., savanna habitat) increased during the first half of the study but declined during the second half. Bird species associated with forest habitats were rare throughout the 41- year period, but their abundance increased during the most recent two decades. Results of this study are important for informing decisions about restoration efforts of riparian forests and other native wooded areas in the Great Plains and setting expectations for the time- scale required for the return of assemblages of species of woodland birds

Estimating offsets for avian displacement effects of anthropogenic impacts

Biodiversity offsetting, or compensatory mitigation, is increasingly being used in temperate grassland ecosystems to compensate for unavoidable environmental damage from anthropogenic developments such as transportation infrastructure, urbanization, and energy development. Pursuit of energy independence in the United States will expand domestic energy production. Concurrent with this increased growth is increased disruption to wildlife habitats, including avian displacement from suitable breeding habitat. Recent studies at energy-extraction and energy-generation facilities have provided evidence for behavioral avoidance and thus reduced use of habitat by breeding waterfowl and grassland birds in the vicinity of energy infrastructure. To quantify and compensate for this loss in value of avian breeding habitat, it is necessary to determine a biologically based currency so that the sufficiency of offsets in terms of biological equivalent value can be obtained. We describe a method for quantifying the amount of habitat needed to provide equivalent biological value for avifauna displaced by energy and transportation infrastructure, based on the ability to define five metrics: impact distance, impact area, pre-impact density, percent displacement, and offset density. We calculate percent displacement values for breeding waterfowl and grassland birds and demonstrate the applicability of our avian-impact offset method using examples for wind and oil infrastructure. We also apply our method to an example in which the biological value of the offset habitat is similar to the impacted habitat, based on similarity in habitat type (e.g., native prairie), geographical location, land use, and landscape composition, as well as to an example in which the biological value of the offset habitat is dissimilar to the impacted habitat. We provide a worksheet that informs potential users how to apply our method to their specific developments and a framework for developing decision-support tools aimed at achieving landscape-level conservation goals