Donald H. Wolfe

Avoidance Behavior by Prairie Grouse: Implications for Development of Wind Energy

New wind-energy facilities and their associated power transmission lines and roads are being constructed at a rapid pace in the Great Plains of North America. Nevertheless, little is known about the possible negative effects these anthropogenic features might have on prairie birds, one of the most threatened groups in North America. We examined radiotelemetry tracking locations of Lesser Prairie-Chickens (Tympanuchus pallidicinctus) and Greater Prairie-Chickens (T. cupido) in two locations in Oklahoma to determine whether these birds avoided or changed movement behavior near power lines and paved highways. We tracked 463 Lesser Prairie-Chickens (15,071 tracking locations) and 216 Greater Prairie-Chickens (5,750 locations) for 7 and 3 years, respectively. Individuals of both species avoided power lines by at least 100 m and Lesser Prairie-Chickens avoided one of the two highways by 100 m. Prairie-chickens crossed power lines less often than expected if birds moved randomly (p < 0.05) but did not appear to perceive highways as a movement barrier (p > 0.05). In addition, home ranges of Lesser Prairie-Chickens overlapped the power line less often than would be expected by chance placement of home ranges; this result was supported by kernel-density estimation of home ranges. It is likely that new power lines (and other tall structures such as wind turbines) will lead to avoidance of previously suitable habitat and will serve as barriers to movement. These two factors will likely increase fragmentation in an already fragmented landscape if wind energy development continues in prairie habitats.

Causes and Patterns of Mortality in Lesser Prairie-chickens Tympanuchus pallidicinctus and Implications for Management

Abstract Life-history studies of prairie grouse have focused on reproductive ecology, habitat use, movement patterns and survivorship, with only cursory or anecdotal references to mortality causes, or they have been of insufficient duration or scale to infer mortality patterns. Because mortality causes and patterns affect other life-history traits, their determination adds to our overall understanding of grouse demographics. As part of a long-term study on lesser prairie-chicken Tympanuchus pallidicinctus natural history in Oklahoma and New Mexico, we recovered 322 carcasses of radio-tagged birds captured on leks. We were able to determine the cause of death for 260 of these birds. Predation by raptors accounted for the largest number of mortalities (91), followed by collisions with fences (86), predation by mammals (76), collisions with power lines (4), and collisions with automobiles (3). Mortality causes differed considerably between study sites and between sexes, with all collisions more frequent in Oklahoma than in New Mexico, in females than in males, and in older than in young females. Although predation is a major cause of mortality, we argue that predator control may not be effective for grouse conservation. Moreover, in cases where top predators reduce mesopredator population densities, for example those of red foxes Vulpes vulpes, indiscriminate removal of predators may hasten the decline of grouse populations. Land managers striving to conserve prairie-chickens and other grouse species should attempt to reduce or eliminate collision mortality risks in addition to efforts to improve nesting or brood-rearing habitat. Collision risks should also be evaluated for potential release sites of translocated or captive-reared grouse.

Habitat Edge, Land Management, And Rates Of Brood Parasitism In Tallgrass Prairie

Bird populations in North Americas grasslands have declined sharply in recent decades. These declines are traceable, in large part, to habitat loss, but management of tallgrass prairie also has an impact. An indirect source of decline potentially associated with management is brood parasitism by the Brown-headed Cowbird (Molothrus ater), which has had substantial negative impacts on many passerine hosts. Using a novel application of regression trees, we analyzed an extensive five-year set of nest data to test how management of tallgrass prairie affected rates of brood parasitism. We examined seven landscape features that may have been associated with parasitism: presence of edge, burning, or grazing, and distance of the nest from woody vegetation, water, roads, or fences. All five grassland passerines that we included in the analyses exhibited evidence of an edge effect: the Grasshopper Sparrow (Ammodramus savannarum), Henslows Sparrow (A. henslowii), Dickcissel (Spiza americana), Red-winged Blackbird (Agelaius phoeniceus), and Eastern Meadowlark (Sturnella magna). The edge was represented by narrow strips of woody vegetation occurring along roadsides cut through tallgrass prairie. The sparrows avoided nesting along these woody edges, whereas the other three species experienced significantly higher (1.9-5.3x) rates of parasitism along edges than in prairie. The edge effect could be related directly to increase in parasitism rate with decreased distance from woody vegetation. After accounting for edge effect in these three species, we found evidence for significantly higher (2.5-10.5x) rates of parasitism in grazed plots, particularly those burned in spring to increase forage, than in undisturbed prairie. Regression tree analysis proved to be an important tool for hierarchically parsing various landscape features that affect parasitism rates. We conclude that, on the Great Plains, rates of brood parasitism are strongly associated with relatively recent road cuts, in that edge effects manifest themselves through the presence of trees, a novel habitat component in much of the tallgrass prairie. Grazing is also a key associate of increased parasitism. Areas managed with prescribed fire, used frequently to increase forage for grazing cattle, may experience higher rates of brood parasitism. Regardless, removing trees and shrubs along roadsides and refraining from planting them along new roads may benefit grassland birds.

It's Not Easy Being Green: Wind Energy and a Declining Grassland Bird

The lesser prairie-chicken (Tympanuchus pallidicinctus) is an umbrella species for the short- and mixed-grass prairie ecosystem of the south-central United States. This species has suffered large population declines over the last century that mirror the loss of prairie. Populations have become increasingly fragmented, and habitat connections between populations are being severed. A possible new threat to lesser prairie-chickens is the rapid development of wind-energy facilities throughout their habitat. In addition to contributing to the loss of prairie, these facilities could serve as barriers to movement if birds avoid wind turbines and their associated power transmission lines. We summarize evidence for avoidance behavior in birds, propose connectivity areas between distributional cores, propose strategies for conservation of lesser prairie-chickens, and encourage lawmakers to adopt state and federal regulations on wind-farm placement. Without a concerted effort, lesser prairie-chickens and similar species are likely to disappear, as will the southern prairie on which they depend.

Genetic variation within and among fragmented populations of lesser prairie-chickens (Tympanuchus pallidicinctus).

As a result of recurrent droughts and anthropogenic factors, the range of the lesser prairie‐chicken (Tympanuchus pallidicinctus) has contracted by 92% and the population has been reduced by approximately 97% in the past century, resulting in the smallest population size and most restricted geographical distribution of any North American grouse. We examined genetic variation through DNA sequence analysis of 478 base pairs of the mitochondrial genome and by assaying allelic variation at five microsatellite loci from lesser prairie‐chickens collected on 20 leks in western Oklahoma and east‐central New Mexico. Traditional population genetic analyses indicate that lesser prairie‐chickens maintain high levels of genetic variation at both nuclear and mitochondrial loci. Although some genetic structuring among lesser prairie‐chicken leks was detected within Oklahoma and New Mexico for both nuclear and mitochondrial loci, high levels of differentiation were detected between Oklahoma and New Mexico populations. Nested‐clade analysis of mitochondrial haplotypes revealed that both historic and contemporary processes have influenced patterns of haplotype distributions and that historic processes have most likely led to the level of differentiation found between the Oklahoma and New Mexico populations.

Factors affecting female space use in ten populations of prairie chickens

Conservation of wildlife depends on an understanding of the interactions between animal movements and key landscape factors. Habitat requirements of wide-ranging species often vary spatially, but quantitative assessment of variation among replicated studies at multiple sites is rare. We investigated patterns of space use for 10 populations of two closely related species of prairie grouse: Greater Prairie- Chickens (Tympanuchus cupido) and Lesser Prairie-Chickens (T. pallidicinctus). Prairie chickens require large, intact tracts of native grasslands, and are umbrella species for conservation of prairie ecosystems in North America. We used resource utilization functions to investigate space use by female prairie chickens during the 6-month breeding season from March through August in relation to lek sites, habitat conditions, and anthropogenic development. Our analysis included data from 382 radio-marked individuals across a major portion of the extant range. Our project is a unique opportunity to study comparative space use of prairie chickens, and we employed standardized methods that facilitated direct comparisons across an ecological gradient of study sites. Median home range size of females varied ;10-fold across 10 sites (3.6-36.7 km 2 ), and home ranges tended to be larger at sites with higher annual precipitation. Proximity to lek sites was a strong and consistent predictor of space use for female prairie chickens at all 10 sites. The relative importance of other predictors of space use varied among sites, indicating that generalized habitat management guidelines may not be appropriate for these two species. Prairie chickens actively selected for prairie habitats, even at sites where ;90% of the land cover within the study area was prairie. A majority of the females monitored in our study (.95%) had activity centers within 5 km of leks, suggesting that conservation efforts can be effectively concentrated near active lek sites. Our data on female space use suggest that lek surveys of male prairie chickens can indirectly assess habitat suitability for females during the breeding season. Lek monitoring and surveys for new leks provide information on population trends, but can also guide management actions aimed at improving nesting and brood-rearing habitats.

Hierarchical cues in brood parasite nest selection

Numerous hypotheses have been developed to explain how a brood parasite selects a host nest into which it lays its eggs. Most hypotheses address various aspects of nest placement. We used an extensive dataset to tease apart the relative strength of various hypotheses associated with nest placement and timing. These data were from North American tallgrass prairie and included nearly 2,000 nests of 17 host species known to accept eggs of the brood parasitic Brown-headed cowbird Molothrus ater. Regression tree analyses, with host species as a categorical covariate built around successive logistic regressions, implied that the “edge effect” and “perch proximity” hypotheses, the latter assessed as distance to woody vegetation, received the strongest support. Hypotheses concerning nest height, livestock proximity, habitat density, nest exposure, laying date, and host clutch size received weaker or subsidiary support, the latter meaning that the hypotheses received significant support only after edge effects or distance to woody vegetation were accounted for first. Host species was associated significantly with parasitism rate, but host species was itself correlated with various vegetation and landscape variables that we assessed. Brood parasitism rate and nest height were associated non-linearly. In addition to a clear hierarchical pattern among factors associated with rates of parasitism, several key explanatory variables had marked interactions, such as prairie edge and extent of woody vegetation or nest height and nest exposure. Such interactions, including between host species and certain landscape and vegetation variables, such as nest height and distance from woody vegetation, suggest caution is warranted when assessing the various competing hypotheses, which are not mutually exclusive.ZusammenfassungEs gibt zahlreiche Hypothesen zur Erklärung, wie ein Brutparasit ein Nest für die eigene Eiablage aussucht, wobei sich die meisten dieser Hypothesen an der spezifischen Lage der Nester ausrichten. Wir benutzten eine umfangreiche Datensammlung, um die relative Stärke derjenigen Hypothesen zu entwirren, die sich auf Nestlage und Eiablage-Zeitpunkt beziehen. Die Daten stammten aus der nordamerikanischen Tallgrass-Prärie, von fast 2000 Nestern 17 unterschiedlicher Wirtsarten, von denen bekannt ist, daß sie Eier des Brutparasiten Braunkopf-Kuhstärling (Molothrus ater) in ihren Nestern akzeptieren. Regressionsbaumanalysen mit den Wirtsspezies als kategorialen Kovariaten, um sukzessive logistische Regressionen herum gerechnet, unterstützten am stärksten die Hypothesen zum„ Rand-Effekt“ und zur „Sitzplätze-Nähe“ (Entfernung zu Gebüsch-Vegetation). Andere Hypothesen, die die Nesthöhe, die Nähe zu Vieh, die Habitatdichte, die Nestlage, oder den Zeitpunkt der Eiablage und die Gelegegröße des Wirtes heranziehen, wurden schwächer oder nur „subsidiär“ unterstützt – wobei letzteres bedeutet, dass diese Hypothesen nur dann signifikant unterstützt wurden, wenn die „Rand-Effekte“ oder die Nähe zu buschiger Vegetation als erstes berücksichtigt wurden. Die Wirtsspezies hingen signifikant mit der Parasitismus-Rate zusammen, aber die Wirtsspezies selbst korrelierten mit diversen, ebenfalls untersuchten Vegetations-und Landschafts-Variablen. „Brutparasitismus-Rate“ und „Nesthöhe“ hingen nicht-linear voneinander ab. Zusätzlich zu einem klaren hierarchischen Muster derjenigen Faktoren, die mit der Brutparasitismus-Rate verknüpft sind, stellten sich einige Schlüsselfaktoren als miteinander verknüpfte Variablen heraus, wie z.B. die Lage an Prärie-Rändern und die Ausprägung buschiger Vegetation, oder Nesthöhe und -lage. Solche Zusammenhänge, inklusive der zwischen Wirtsspezies und bestimmten Landschafts- und Vegetations-Variablen wie der Nesthöhe und der Entfernung zu den nächsten Gebüschen, raten bei der Untersuchung der verschiedenen miteinander konkurrierenden, sich nicht gegenseitig ausschließenden Hypothesen zur Vorsicht.

Lesser Prairie-Chicken Hen and Brood Habitat Use on Sand Shinnery Oak

Abstract The structural attributes of shrubland communities may provide thermal refugia and protective cover necessary for wild animals to survive. During the summers of 2002 and 2003, we evaluated the thermal environment for lesser prairie-chicken (Tympanuchus pallidicinctus Ridgway) broods in southeast New Mexico across a complex landscape that included grazed sand shinnery oak (Quercus havardii Rydb.), ungrazed sand shinnery oak treated with tebuthiuron, sand dunes, cropland, and Conservation Reserve Program native grass plantings. Based on data from 257 brood locations and 53 random locations, lesser prairie-chicken broods selected locations based on sand shinnery oak dominance, with taller plant heights and more over-head cover, when temperatures exceeded 26.4°C than what was randomly available. Prairie chickens selected areas not treated with herbicide and these sites were often selected at a fine spatial scale. These data support other studies suggesting that there may be no justification of shrub control for lesser prairie-chicken conservation within the sand shinnery oak communities.

Fine-Scale Selection of Habitat by the Lesser Prairie-Chicken

Abstract Proper management of grasslands and shrublands requires an understanding of the factors that influence the persistence of organisms. We compare differences in vegetation between sites occupied by the lesser prairie-chicken (Tympanuchus pallidicinctus) and random sites to investigate composition of grasses and forbs and the importance of cover. We observed that birds selected habitat, at least in part, based on composition of grasses and forbs. There was generally a larger variance in diversity of plants for random sites compared to sites associated with presence of lesser prairie-chicken. The role of vegetative cover in selection of habitat is important for avoidance of predators, but use of cover also is a means of thermoregulation. Risk-sensitive behavior is a trade-off between avoiding predation and suitable microclimate. We report evidence that the lesser prairie-chicken consistently seeks to limit the risk of predation and selects locales with a favorable microclimate; birds select sites more or less exposed depending on apparent temperature. We infer that selection of habitat by the lesser prairie-chicken is the result of composition of species of plants, avoidance of predators, and thermoregulation, with the lekking mating system of this bird also playing a role. This declining species might face increasing threats as some practices of land management alter structure of vegetation and reduce shrub cover. Resumen El manejo adecuado de los pastizales y matorrales requiere una comprensión de los factores que influyen en la persistencia de los organismos. Se comparan las diferencias de vegetación entre sitios ocupados por el pollo de la pradera menor (Tympanuchus pallidicinctus) y sitios al azar para investigar la composición de pastos y hierbas y la importancia de la cubierta. Observamos que las aves seleccionaron el hábitat, al menos en parte, basándose en la composición de pastos y hierbas. En general hubo una variación mayor en la diversidad de la vegetación de los sitios al azar en comparación con los sitios asociados con la presencia del pollo de la pradera menor. El papel de la cubierta vegetal en la selección de hábitat es importante para evitar a los depredadores, pero el uso de la cubierta es también un medio de termorregulación. El comportamiento sensible al riesgo es una concesión mutua entre evitar la depredación y conseguir un microclima adecuado. Se presenta evidencia de que el pollo de la pradera menor constantemente trata de limitar el riesgo de depredación y de seleccionar lugares con un microclima favorable; las aves seleccionan los sitios más o menos expuestos dependiendo de la temperatura ambiental. Se infiere que la selección del hábitat del pollo de la pradera menor es el resultado de la composición de especies de plantas, de evitar a los depredadores, y de la termorregulación, con el sistema de apareamiento lek de esta ave también jugando un papel importante. Esta especie en declive puede encontrar amenazas crecientes debido a que algunas prácticas de manejo de la tierra alteran la estructura de la vegetación y reducen la cobertura de arbustos.

Low effective population size and survivorship in a grassland grouse

Assessments of census size (Nc) and effective population size (Ne) are necessary for the conservation of species exhibiting population declines. We examined two populations (Oklahoma and New Mexico) of the lesser prairie-chicken (Tympanuchus pallidicinctus), a declining lek-breeding bird, in which one population (Oklahoma) has larger clutch size and more nesting attempts per year but lower survival caused by human changes to the landscape. We estimated demographic and genetic estimates of Ne for each population and found that both populations have low Ne estimates with a risk of inbreeding depression. Although Oklahoma females produce a larger number of offspring, the proportion of females successfully reproducing is not higher than in New Mexico. Higher reproductive effort has likely reached a physiological limit in Oklahoma prairie-chickens but has not led to a higher Ne or even a larger Nc than New Mexico. We propose that future conservation efforts focus on maximizing survivorship and decreasing the variance in reproductive success because these factors are more likely than increasing reproductive output alone to yield population persistence in lek-breeding species.