Time filter

Source Type

West Baraboo, WI, United States

Booms T.L.,Alaska Department of Fish and Game | Holroyd G.L.,Environment Canada | Gahbauer M.A.,Migration Research Foundation | Trefry H.E.,Natural Resources Canada | And 7 more authors.
Journal of Wildlife Management | Year: 2014

The North American Breeding Bird Survey, Christmas Bird Count, and regional and national conservation assessments provide convincing evidence that the short-eared owl (Asio flammeus) is experiencing a range-wide, long-term decline in abundance in North America. However, the species has received little conservation or research attention. The short-eared owl is vulnerable to decline because it relies heavily on large, intact grasslands and a specialized diet of unpredictable small mammal prey. The species' nomadic movements compound these vulnerabilities by making a decline difficult to detect with current monitoring programs while obfuscating stewardship responsibilities for managers. The primary threat to the species is loss, fragmentation, and degradation of large tracts of native grasslands and wetlands. We propose the following conservation priorities to better understand and begin addressing the short-eared owl's decline: 1) better define and protect important habitats; 2) improve population monitoring; 3) determine seasonal and annual movements; 4) re-evaluate NatureServe's short-eared owl national conservation classifications; 5) develop management plans and tools; and 6) classify raptors, including short-eared owls, as migratory birds in Canada. We contend that the short-eared owl's need for habitat conservation at large spatial scales, status as a predator, and high reproductive potential that affords the species capacity to recover, make it an effective and useful candidate as an umbrella species for grassland conservation. © 2014 The Wildlife Society. Source

Johnson D.H.,Global Owl Project | Swengel S.R.,909 Birch Street | Swengel A.B.,909 Birch Street
Journal of Raptor Research | Year: 2013

We assembled Short-eared Owl (Asio flammeus) abundance data from Buena Vista Grassland, Wisconsin, for the period 1955-2011, primarily from the Hamerstrom (1955-94) and Swengel (1997-2011) research teams. We also gathered owl breeding-season observation data from the Wisconsin state ornithology journal (Passenger Pigeon). We tabulated the number of owl breeding areas based on adult territoriality, nests, and family groups, and classified each year's breeding season by abundance categories. Summer detections and evidence of breeding for Short-eared Owls at Buena Vista varied greatly among years in both the Hamerstrom and Swengel datasets. Peak owl years occurred rarely and unpredictably. During the 57 yr of this study we report three very high peak years of owl abundance (1970, 1974, 2000), three high years (2001, 2006, 2009), 11 mid-range years, 13 low years, 14 no-owl years, and 13 years with missing data inferred from corroborative analysis to be low or no-owl years. The data did not reveal a strong cyclical pattern in owl abundance or suggest a directed population trend. We extracted vole (Microtus) abundance data for 1964-83 from the Hamerstrom dataset. All pairwise correlations of owl abundance (abundance categories, number of breeding areas) and vole abundance (ranking, abundance categories) were strongly and positively significant. © 2013 The Raptor Research Foundation, Inc. Source

Swengel A.B.,909 Birch Street | Swengel S.R.,909 Birch Street
Journal of Insect Conservation | Year: 2015

We surveyed butterflies in prairies, pine-oak barrens, and degraded grasslands during 1988–2013 in southern Wisconsin, USA. In prairie preserves (primarily managed with frequent fire), both specialist and non-specialist “grassland” grass-skippers declined strongly. Specialists inhabiting the native herbaceous flora of pine-oak barrens that had little management but relatively consistent vegetation over time had large fluctuations but more stable trends. Grassland grass-skippers showed similar more stable trends in barrens and degraded fields with relatively consistent vegetation over time. Significant population trends did not relate clearly to how southerly the species’ ranges are. Specialist and grassland grass-skipper persistence after prairie preservation correlated negatively with both number of years since preservation and prairie patch size. We also analyzed grass-skipper abundance during 1977–2012 in midwestern 4th of July Butterfly Counts, an annual volunteer butterfly census. Specialists declined significantly but grassland as well as forest and wetland grass-skippers averaged a non-trend. We hypothesize that the reasons why fire management is adverse are because of direct mortality and also the thick tall grass regrowth, which may be unsuitable for larvae to use. It appears urgent to identify and implement management strategies in prairie preserves that consistently maintain grassland vegetation as required by grass-skippers in ways the grass-skippers themselves tolerate. © 2015, The Author(s). Source

Swengel S.R.,909 Birch Street | Swengel A.B.,909 Birch Street
Journal of Insect Conservation | Year: 2015

During 2002–2013, we surveyed butterflies in three types of bogs (pristine but naturally fragmented). Of the 75 bogs surveyed, we established 29 bogs and 5 bog roadsides as long-term sites visited annually for 9–15 years. We studied patterns of ten butterfly species’ flight periods, annual variation, trend in abundance over time, and abundance with respect to climatic variables. First observed date per year varied more for spring than summer species. Jutta arctic Oeneis jutta varied between dramatically high numbers in odd years and low numbers in even years in northeast Wisconsin. Elsewhere, Jutta arctic varied less between odd and even years, but muskegs had higher numbers in even than odd years, significantly so in north central Wisconsin. The most abundant bog affiliate (tyrphophile), brown elfin Callophrys augustinus, exhibited cyclic abundance over a 4–5 year period. The other species varied greatly in abundance among years but not in as distinctive annual patterns. The most northern specialist (tyrphobiont), purplish fritillary Boloria montinus, declined strongly. Its abundance significantly related to higher precipitation but not to temperature. Population trends for the seven other tyrphobionts did not relate to how southerly their ranges are. Trends in roadsides were less favorable than in bogs. Butterfly abundance had more significant correlations to climate variables related to moisture than to temperature. Based on abundance relationships to climate, a majority of the study species allied as dry steppe species (increasing in warmer, drier periods) and a minority as wetland species (increasing in cooler, wetter periods). The overriding factors determining the future of this butterfly fauna appear to be habitat degradation and potential climate change beyond the range of variation typically experienced in this region between glaciations. © 2014, The Author(s). Source

Swengel A.B.,909 Birch Street | Swengel S.R.,909 Birch Street
Insects | Year: 2013

We counted butterflies on transect surveys during Hesperia ottoe flight period in 1988-2011 at tallgrass prairie preserves in four states (Illinois, Iowa, Minnesota, Wisconsin), divided into units cross-referenced to vegetation type and management history. H. ottoe occurred only in dry and sand prairie types, and was significantly more abundant in undegraded than semi-degraded prairie, and in discontinuous sod (with numerous unvegetated areas due to bare sand and/or rock outcrops) than in continuous sod. This skipper was significantly more abundant in small sites compared to medium and large sites, even when the analysis was limited to undegraded prairie analyzed separately by sod type. H. ottoe was significantly under-represented in year-burn 0 (the first growing season after fire) compared to an expected distribution proportional to survey effort. However, H. ottoe was also over-represented in fire-managed units compared to non-fire-managed units. However, by far most units and sites were in fire management and most populations declined to subdetection during this study. Peak abundance post-fire occurred in a later year-burn in discontinuous sod and was much higher than in continuous sod. We also analyze H. ottoe status and trend in midwestern prairie preserves by compiling a dataset of our and others' butterfly surveys from 1974 to 2011. Only 1/9 sites with continuous sod had detectable H. ottoe in recent year(s). In discontinuous sod, 2/6 did, with two sites lacking data for the last few years. The number of years H. ottoe was still detectable after preservation and the number of years to consistent non-detection were both significantly higher in discontinuous than continuous sod. Both measures of population persistence averaged over twice as long in discontinuous than continuous sod, and correlated negatively with prairie size. The year when consistent non-detection began varied over several decades among sites. Despite the currently urgent need to identify how to manage preserves successfully for H. ottoe, such research now needs to be very cautious, because of the extreme fragility of the few remaining populations and the ruggedness of the preserves where H. ottoe is still known to occur. © 2013 by the authors; licensee MDPI, Basel, Switzerland. Source

Discover hidden collaborations