Clayton H. Riddell Faculty of Environment, Earth, and Resources Scholarly Works

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Open Access
A meta-collection of nitrogen stable isotope data measured in Arctic marine organisms from the Canadian Beaufort Sea, 1983–2013
(2021-09-06) Ehrman, Ashley; Hoover, Carie; Giraldo, Carolina; MacPhee, Shannon A.; Brewster, Jasmine; Michel, Christine; Reist, James D.; Power, Michael; Swanson, Heidi; Niemi, Andrea; Walkusz, Wojciech; Loseto, Lisa
Abstract Objectives Existing information on Arctic marine food web structure is fragmented. Integrating data across research programs is an important strategy for building a baseline understanding of food web structure and function in many Arctic regions. Naturally-occurring stable isotope ratios of nitrogen (δ15N) and carbon (δ13C) measured directly in the tissues of organisms are a commonly-employed method for estimating food web structure. The objective of the current dataset was to synthesize disparate δ15N, and secondarily δ13C, data in the Canadian Beaufort continental shelf region relevant to trophic and ecological studies at the local and pan-Arctic scales. Data description The dataset presented here contains nitrogen and carbon stable isotope ratios (δ15N, δ13C) measured in marine organisms from the Canadian Beaufort continental shelf region between 1983 and 2013, gathered from 27 published and unpublished sources with associated sampling metadata. A total of 1077 entries were collected, summarizing 8859 individual organisms/samples representing 333 taxa across the Arctic food web, from top marine mammal predators to primary producers.
Open Access
A New Trophic State Index for Lagoons
(2014-3-9) Gupta, Mukesh
This paper proposes a new nitrogen-based trophic state index (TSI) for the estimation of status of eutrophication in a lagoon system. Nitrite-nitrogen (NO2-N) is preferable because of its greater abundance in Chilika lagoon and its relation to other criteria of trophic state, for example, chlorophyll-a (Chl-a) and Secchi disk depth (SDD). Nitrite is preferable over nitrate because the former decreases the fluorescence and affects photosynthesis, thereby controlling primary production. This paper also computes TSI using Chl-a and SDD. The three parameters account for the biological, chemical, and physical characteristics of the lagoon. It will be possible to estimate the TSI of freshwater and brackish water lagoons and other water bodies using the new expressions taking into consideration the spatial and temporal variability in the dataset. Depending on the data availability, alternative TSI (Chl-a) and TSI (SDD) can account for the biological and physical contributions to eutrophication. The estimated TSI can account for Chl-a and NO2-N up to 322.18 mg m−3 and 61.99 μg L−1, respectively. The TSI based on these three parameters can serve as a complimentary and predictive tool for lagoon management and field programs to monitor the health of a lagoon.
Open Access
A resource management scenario for traditional and scientific management of pink shrimp (Farfantepenaeus paulensis) in the Patos Lagoon estuary (RS), Brazil
(2013-01-11) Moura, Gustavo Goulart Moreira; Kalikoski, Daniela Coswig; Diegues, Antonio Carlos Sant’Ana
Abstract Background This article aims to discuss the incorporation of traditional time in the construction of a management scenario for pink shrimp in the Patos Lagoon estuary (RS), Brazil. To meet this objective, two procedures have been adopted; one at a conceptual level and another at a methodological level. At the conceptual level, the concept of traditional time as a form of traditional ecological knowledge (TEK) was adopted. Method At the methodological level, we conduct a wide literature review of the scientific knowledge (SK) that guides recommendations for pink shrimp management by restricting the fishing season in the Patos Lagoon estuary; in addition, we review the ethno-scientific literature which describes traditional calendars as a management base for artisanal fishers in the Patos Lagoon estuary. Results Results demonstrate that TEK and SK describe similar estuarine biological processes, but are incommensurable at a resource management level. On the other hand, the construction of a “management scenario” for pink shrimp is possible through the development of “criteria for hierarchies of validity” which arise from a productive dialog between SK and TEK. Conclusions The commensurable and the incommensurable levels reveal different basis of time-space perceptions between traditional ecological knowledge and scientific knowledge. Despite incommensurability at the management level, it is possible to establish guidelines for the construction of “management scenarios” and to support a co-management process.
Open Access
Ability to alter song in two grassland songbirds exposed to simulated anthropogenic noise is not related to pre-existing variability.
(Taylor and Francis, 2018) Curry, Claire M.; Antze, Bridget; Warrington, Miyako H.; Des Brisay, Paulson G.; Koper, Nicola
Organisms encounter noise naturally in the environment. However, increasing prevalence of human-caused noise seems to be resulting in behavioural changes in many animals that can affect survival and reproduction. Not all species react the same way to noise; some adjust their vocal signals while others do not. We hypothesized that species with more variability in their vocal signals would be better able to adjust their signals to be audible over anthropogenic noise. We tested this within a large-scale manipulative experiment by recording songs of two grassland songbirds, Baird’s sparrow (Ammodramus bairdii) and Savannah sparrow (Passerculus sandwichensis), both of which are found in areas increasingly affected by energy extraction noise. We compared these species because Savannah sparrows have more variability in their songs geographically and temporally compared to Baird’s sparrows. We recorded both species’ songs before, during, and after high-fidelity playbacks of oil well drilling noise. Surprisingly, both species changed parts of their songs in the presence of noise (Baird’s sparrow usually decreasing frequency and Savannah sparrow increasing frequency) and these changes were not related to seasonal, song, or syllable variability. We suggest instead that acoustically heterogeneous environments may favor the evolution of species that are capable of adjusting their songs in response to variable ambient noise.
Open Access
Adaptive learning, technological innovation and livelihood diversification: the adoption of pound nets in Rio de Janeiro State, Brazil
(2012-06-06) Idrobo, Carlos J; Davidson-Hunt, Iain J
AbstractThis paper examines the adoption of a technology to appropriate an ecologically constrained resource within the context of a restructuring fisheries sector utilising the conceptual lenses of adaptive learning and practice. Participant observation and semi-structured interviews were undertaken in the coastal community of Ponta Negra, Paraty, Rio de Janeiro, Brazil, from May 2010 to March 2011. The materials collected were translated and transcribed into English and then manually coded. Through a restorying process the English transcripts were developed into an analytical narrative that described the process of the adoption of pound nets and how this initiated a process of social differentiation between fishing households. The pound net technology constituted a new field of practice that both created and constrained opportunities for livelihood diversification. In this case, individual adaptations made to diversify household economies initiated a cascading process of social differentiation within a coastal community.
Open Access
Anthropogenic landscape changes and their impacts on terrestrial and freshwater soundscapes
(Springer, 2019) Proulx, Raphael; Waldinger, Jessica; Koper, Nicola
Purpose of review: Quantifying the effects of anthropogenic sounds on wildlife at the landscape scale of observation has been notoriously difficult because these sounds are often confounded with the presence of infrastructure and loss of habitat through resource exploitation activities. In this paper, we review how anthropogenic landscape changes affect the power level and propagation of sounds in both terrestrial and freshwater ecosystems, as well as the behavioural response of organisms to novel acoustic habitats. Recent findings: Resource exploitation and other human activities change soundscapes both directly, by affecting sound production and propagation, and indirectly, by modifying landscape structure and species distribution patterns. Intermittent anthropogenic sounds are concentrated in the lower frequencies, tend to be louder than enduring sounds of the same origin, and create more patchy soundscapes. We identified key sensorial traits that are related to the auditory acuity of species in different taxonomic groups, including fish, birds, anurans, stridulating insects, and small mammals, and which may help us understand why certain species are more sensitive to anthropogenic changes to soundscapes. Summary: Prioritizing research in an increasingly noisy world requires a proper understanding of the auditory sensitivity of species, the characteristics of anthropogenic sounds (i.e., intermittent or enduring), and how sound production and propagation is affected by landscape structure. Further research on species’ sensorial traits would provide a framework with which to scale responses to anthropogenic sounds from individuals to communities, and better predict the impact of human activities on terrestrial and freshwater ecosystems.
Open Access
Assessing the Breeding Success of the Western Grebe (Aechmophorus occidentalis) After 40 Years of Environmental Changes at Delta Marsh, Manitoba
(The Waterbird Society, 2014) La Porte, Nicholas; Koper, Nicola; Leston, Lionel
Since the 1970s, artiﬁcially stabilized water levels, increased presence of common carp (Cyprinus carpio) and invasion by a cattail hybrid (Typha glauca) have changed the nesting environment for Western Grebes (Aechmophorus occidentalis) at Delta Marsh, Manitoba. To evaluate the impact of these changes, nest survival rates, causes of nest mortality, wind conditions, locations of nests and vegetation structure at nests in 2009-2010, and chick-adult ratios were compared to similar data for Western Grebes at Delta Marsh from 1973-1974. Apparent nest survival rates were lower in 2009-2010 than 1973-1974, and between low-water years (1973, 2010) and high-water years (1974, 2009). Lower apparent nest survival rates in 2009-2010 (49% in 2009 and 43% in 2010, compared to 46% in 1973 and 84% in 1974), and chick-adult ratios (0.55 in 1973 and 0.88 in 1974, compared to 0.55 in 2009 and 0.39 in 2010) were attributed to increases in destruction of nests primarily by wave action and secondarily by common carp, which were not observed destroying Western Grebe nests in 1973-1974. The replacement of native bulrushes by cattails in Western Grebe nesting habitat may have caused the observed increase in proximity to openwater edge, and this proximity may have increased destruction of nests by waves. Restoring stands of emergent bulrush by varying marsh water levels and reducing carp in the marsh might improve nest survival of Western Grebes.
Open Access
C-Band Polarimetric Coherences and Ratios for Discriminating Sea Ice Roughness
(2013-5-22) Gupta, Mukesh; Scharien, Randall K.; Barber, David G.
The rapid decline of sea ice in the Arctic has resulted in a variable sea ice roughness that necessitates improved methods for efficient observation using high-resolution spaceborne radar. The utility of C-band polarimetric backscatter, coherences, and ratios as a discriminator of ice surface roughness is evaluated. An existing one-dimensional backscatter model has been modified to two-dimensions (2D) by considering deviation in the orientation (i.e., the slopes) in azimuth and range direction of surface roughness simultaneously as an improvement in the model. It is shown theoretically that the circular coherence () decreases exponentially with increasing surface roughness. The crosspolarized coherence () is found to be less sensitive to surface roughness, whereas the copolarized coherence () decreases at far-range incidence angles for all ice types. A complete validation of the adapted 2D model using direct measurements of surface roughness is suggested as an avenue for further research.
Open Access
Cattle stocking rate and grazing duration effects on songbird nest survival vary by species in mixed-grass prairies
(Elsevier, 2016) Pipher, Emily; Curry, Claire M.; Koper, Nicola
Grassland bird species are declining more quickly than birds of any other biome in North America, but the effects of the most widespread use of native mixed-grass prairies, livestock grazing, on nest survival of songbirds is not well understood. We used an adaptive management grazing experiment in southwestern Saskatchewan to evaluate effects of cattle stocking rate and number of years grazed on nest survival of five songbird species in 2009 and 2010. Two 300-m² plots were located in each of 12 pastures. Three pastures were ungrazed controls, while the remaining pastures had stocking rates ranging from 0.23-0.83 Animal Unit Months (AUM) · ha-1 (very low to very high for this region), and were grazed for 2-3 or >15 years. Analyses were conducted using logistic exposure regression. We found few effects of grazing on nest survival. Exceptions to this pattern were that the lowest nest survival rates occurred at low-moderate grazing intensities with fewer years grazed for Sprague’s pipits (Anthus spragueii) in 2009, at low grazing intensities and longer grazing durations for chestnut-collared longspurs in 2009, and at moderate grazing intensities regardless of grazing duration for vesper sparrows in 2010. Cumulatively, our results suggest that in the short term, a wide range of grazing intensities are consistent with the conservation of grassland songbirds, and that a mosaic of grazing intensities across the prairie landscape would provide preferred habitat types for a variety of songbird species.
Open Access
Direct effects of cattle on grassland birds in Canada
(2014) Bleho, Barbara I.; Machtans, Craig; Koper, Nicola
Effects of grazing on grassland birds are generally thought to be indirect, through alteration of vegetation structure; however, livestock can also affect nest survival directly through trampling and other disturbances (e.g., livestock-induced abandonment). We extracted data on nest fates from 18 grazing studies conducted in Canada. We used these data to assess rates of nest destruction by cattle among 9 ecoregions and between seasonal and rotational grazing systems. Overall, few nests were destroyed by cattle (average 1.5% of 9132 nests). Nest destruction was positively correlated with grazing pressure (i.e., stocking rate or grazing intensity), but nest survival was higher in more heavily grazed areas for some species. Because rates of destruction of grassland bird nests by cattle are low in Canada, management efforts to reduce such destruction may not be of ecological or economic value in Canada.
Open Access
Distinct Ocean Responses to Greenland's Liquid Runoff and Iceberg Melt
(American Geophysical Union, 2021-11-11) Marson, Juliana M.; Gillard, Laura C.; Myers, Paul G.
While Greenland discharge has been increasing in the last decades, its impact on the Meridional Overturning Circulation (MOC) is not clearly established. Because of that, the accuracy of this discharge representation in ocean models has not been a priority in large-scale circulation studies. Many models prescribe Greenland discharge solely as liquid runoff from the coast—even though around half of this mass loss is attributed to solid discharge. In this study, we use sensitivity experiments carried out with the Nucleus for European Modeling of the Ocean general circulation model to show the most relevant impacts that different Greenland solid discharge parameterizations (transforming it to liquid runoff or explicitly representing it through an iceberg model) have on the western subpolar Atlantic. We find that icebergs act as freshwater reservoirs that affect how much, when, and where freshwater is delivered to the ocean. They carry large amounts of freshwater away from boundary currents, releasing it in the interior of the subpolar gyre. Moreover, the amount and variability of freshwater delivered to the ocean depend not only on the characteristics of Greenland discharge itself but also on the environmental conditions icebergs are subjected to. We also find a large difference in subsurface temperatures in the Gulf of Saint Lawrence, which suggests that different Greenland discharge parameterizations might have far reaching implications beyond the MOC. Although differences in ocean fields between the simulations are usually small and within their interannual variability, they might be relevant as Greenland calving rates increase with global warming.
Open Access
Effects of twice-over rotational grazing on songbird nesting success in years with and without flooding
(Elsevier, 2018) Carnochan, Stacey; De Ruyck, Christopher; Koper, Nicola
Rotational grazing is sometimes promoted for grassland bird conservation, but the benefits to wildlife have not been comprehensively documented. We examined effects of twice-over rotational grazing on nesting success of grassland songbirds in south-western Manitoba, Canada in comparison to season-long grazing. We monitored nesting attempts and collected structural vegetation data in 2011 (during a 1/300 flood event), and 2012 (average water levels), for five species of obligate grassland bird species (n=110) and one shrub-nesting species (n=41). Nesting analyses were conducted using logistic exposure models. Nesting success was 2.4-4 times lower in twice-over grazed pastures compared with season-long grazed pastures, perhaps because of the increased cattle density during the short grazing periods of the twice-over system. Nests protected by shrubs from grazing activities of cattle did not show this pattern. Grazing system did not have an effect on vegetation structure. This suggests that twice-over rotational grazing does not benefit grassland songbirds in northern mixed-grass prairies, and that caution must be taken before implementing this grazing system in areas intended to promote biodiversity conservation.
Open Access
Effects of Weather and Land Management on the Western Prairie Fringed-orchid (Platanthera praeclara) at the Northern Limit of its Range in Manitoba, Canada
(2015) Bleho, Barbara I.; Koper, Nicola; Borkowsky, Christie L.; Hamel, Cary D.
The western prairie fringed-orchid is a rare North American orchid restricted to a few remnants of wet to mesic tallgrass prairie. It is federally listed in both Canada and the United States and both countries have developed a recovery plan for the species. Two key management objectives are to monitor population trends and identify beneficial management practices. We used 21 y of data from the Manitoba metapopulation to assess effects of weather and land management on this species. Our results suggest the metapopulation in Manitoba is relatively stable. Western prairie fringed-orchids appear to benefit most from a combination of warm temperatures in the previous growing season followed by cool snowy but short winters and wet springs. Periodic burning ( e.g., every 2-3 y) may benefit fringed-orchids, whereas grazing may be detrimental. This was not a controlled experiment, however, and gaps in the data may have influenced our results. Prescribed burning is a viable management tool for curtailing woody invasion and both burning and grazing reduce litter and grass cover, but careful consideration of timing, frequency, and intensity of application is required so management does not hinder fringed-orchid reproduction or reduce survival, while also recognizing management requirements may vary among years depending on weather. Long-term studies are particularly valuable for the western prairie fringed-orchid due to its erratic life cycle and fluctuating populations, which complicate studies of environmental and management effects on this species.
Open Access
The final frontier: Early-stage genetic introgression and hybrid habitat use in the northwestern extent of the Golden-winged Warbler breeding range
(2018) Moulton, Laurel; Vallender, Rachel; Artuso, Christian; Koper, Nicola
Anthropogenic changes to the landscape and climate have resulted in secondary contact between previously allopatric species. This can result in genetic introgression and reverse speciation when closely related species are able to hybridize. The Golden-winged Warbler has declined or been extirpated across much of its range where it has come into secondary contact with the Blue-winged Warbler. Genetic screening previously showed that introgression had occurred range-wide with the exception of Manitoba, Canada. Our goal was to reassess the genetic status of the Golden-winged Warbler population in Manitoba and to examine the demographics and habitat use of phenotypic and genetic hybrids. From 2011-2014, we sampled and screened mtDNA from 205 Golden-winged Warblers and hybrids in Southeast Manitoba. In 2012, we monitored all Golden-winged Warbler territories within those sites and measured territory- and landscape-level habitat variables. Of the birds screened, 195 had a phenotype that matched their mtDNA type, 2 were phenotypic hybrids, and 8 showed a phenotypic-mtDNA mismatch (cryptic hybrids). We found no difference in the habitat used by Golden-winged Warblers compared with hybrids at either scale. The low proportion of hybrids found in Manitoba and the lack of a distinguishable difference in habitat use by Golden-winged Warblers and hybrids indicates that the exclusion of hybrid birds from Golden-winged Warbler habitat is unlikely to be a successful conservation strategy. The best way to manage for Golden-winged Warblers is to slow the habitat loss and fragmentation that continues within Manitoba and to actively manage early-successional deciduous forest using tools such as fire and logging.
Open Access
Grazing Intensity influences Ground Squirrel and American Badger Habitat Use in Mixed-Grass Prairies
(2014) Bylo, Lindsey, N.; Koper, Nicola; Molloy, Kelsey
Ground squirrel (Spermophilus spp.) and American badger (Taxidea taxus) burrowing activities are ecologically important disturbances that contribute to the heterogeneity of prairie environments. These activities also have a strong impact on habitat suitability for many other grassland species. However, effects of cattle grazing intensity on ground squirrel and American badger burrows are not well understood. From 2006-2012, we evaluated effects of grazing intensity and vegetation type on American badger burrow occurrence and ground squirrel burrow abundance using a manipulative grazing experiment in Grasslands National Park of Canada, Saskatchewan. The study area consisted of nine 300-ha pastures at a range of stocking rates, from very low to very high for the region. Each pasture had ten plots (six upland and four lowland) where vegetation and burrow surveys were completed. Burrow abundance and occurrence, and vegetation structure, were assessed for 2 years prior to the introduction of cattle to this landscape in 2008, which followed at least 15 years without livestock, and from 2009-2012, following introduction of livestock. Data were analyzed using generalized linear mixed models. In upland habitats, ground squirrel burrow counts increased with increasing grazing intensity and decreasing vegetation biomass; conversely, badger burrow occurrence increased with decreased stocking rates and increasing average litter cover and vegetation biomass. Abundance and occurrence of both ground squirrel and badger burrows in lowland habitats was relatively independent of grazing intensity or vegetation. Vegetation composition had little impact on ground squirrel or badger burrows. A range of grazing intensities may contribute to maintaining diversity of burrowing mammals in prairie environments.
Open Access
Growth, sexual maturity, and reproduction of a female Midland Painted Turtle (Chrysemys picta marginata) afflicted with kyphosis
(2015) MOLDOWAN, Patrick, D.; KEEVIL, Matthew, G.; Koper, Nicola; Brooks, Ronald, J.; Litzgus, Jacqueline, D.
Kyphosis, a congenital humpback condition of the spinal column, has been reported across a broad range of chelonian taxa. These reports are often of single observations and lack background information about the history of the animal(s) involved. A kyphotic female Midland Painted Turtle (Chrysemys picta marginata) reported herein is a member of a long-term mark-recapture study in Algonquin Park (Ontario, Canada), providing a unique opportunity to document life-history characters of a kyphotic turtle over 18 years, and to draw comparisons to other members of her cohort and population. Despite this spinal deformity, the somatic growth, body size, age at sexual maturity, and reproduction of the kyphotic female are similar to those of normal (non-kyphotic) females in our long-term study population. This suggests that the condition has not compromised her fitness.
Open Access
Impact of Continuous Cropping on the Diurnal Range of Dew Point Temperature during the Foliar Expansion Period of Annual Crops on the Canadian Prairies
(2015-12-29) Shrestha, Bharat M.; Raddatz, Richard L.; Desjardins, Raymond L.; Worth, Devon E.
It is important to increase our knowledge of the role of land use in changing the regional climate. This study asked, “Has the increase in continuous cropping over the past 50 years on the Canadian Prairies influenced the daily mean and range of morning dew point temperatures during the foliar expansion period (from mid-June to mid-July) of annual field crops?” We found that there has been a general increase in the decadal average of mean daily and in the range of morning from the 1960s to the 2000s. The increase in the observed range of between the daily minimum value, which typically occurs near sunrise, and the late morning peak was found to be related to the increase in annual crop acreage and consequent decrease in summerfallow area. The relationship was more significant in the subhumid climatic zone than in the semiarid climatic zone, and it was influenced by whether the region was experiencing either wet, normal, or dry conditions.
Open Access
Is habitat fragmentation bad for biodiversity?
(Elsevier, 2019) Fahrig, Lenore; Arroyo-Rodríguez, Victor; Bennett, Joseph; Boucher Lalonde, Véronique; Cazetta, Eliana; Currie, David J.; Eigenbrod, Felix; Ford, Adam T.; Harrison, Susan P.; Jaeger, Jochen; Koper, Nicola; Martin, Amanda E.; Martin, Jean-Louis; Metzger, Jean Paul; Morrison, Peter; Rhodes, Jonathan R.; Saunders, Denis A.; Simberloff, Dan; Smith, Adam C.; Tischendorf, Lutz; Vellend, Mark; Watling, James I.
In a review of landscape-scale empirical studies, Fahrig (2017a) found that ecological responses to habitat fragmentation per se (fragmentation independent of habitat amount) were usually non-significant (> 70% of responses) and that 76% of significant relationships were positive, with species abundance, occurrence, richness, and other response variables increasing with habitat fragmentation per se. Fahrig concluded that to date there is no empirical evidence supporting the widespread assumption that a group of small habitat patches generally has lower ecological value than large patches of the same total area. Fletcher et al. (2018) dispute this conclusion, arguing that the literature to date indicates generally negative ecological effects of habitat fragmentation per se. They base their argument largely on extrapolation from patchscale patterns and mechanisms (effects of patch size and isolation, and edge effects) to landscape-scale effects of habitat fragmentation. We argue that such extrapolation is unreliable because: (1) it ignores other mechanisms, especially those acting at landscape scales (e.g., increased habitat diversity, spreading of risk, landscape complementation) that can counteract effects of the documented patch-scale mechanisms; and (2) extrapolation of a small-scale mechanism to a large-scale pattern is not evidence of that pattern but, rather a prediction that must be tested at the larger scale. Such tests were the subject of Fahrig's review. We find no support for Fletcher et al.'s claim that biases in Fahrig's review would alter its conclusions. We encourage further landscape-scale empirical studies of effects of habitat fragmentation per se, and research aimed at uncovering the mechanisms that underlie positive fragmentation effects.
Open Access
Managing Mixed-grass Prairies for Songbirds Using Variable Cattle Stocking Rates
(Elsevier, 2015) Sliwinski, M.S.; Koper, N.
Most remaining grasslands are used for livestock grazing; stocking rates could be managed to help stop declining songbird populations. We examined the effects of stocking rates on grassland songbirds in northern mixed-grass prairies using a beyond Before-After-Control-Impact manipulative experiment in Canada’s Grasslands National Park and adjacent community pastures. The study area consisted of nine 300-ha pastures grazed at a range of stocking rates starting in 2008. We conducted songbird surveys at six upland plots in each pasture from 2006‒2010, and measured vegetation structure within each plot from 2008‒2010 (n = 54). We evaluated the effects of stocking rates on habitat structure and songbird abundance using linear and generalized linear mixed models. Baird’s sparrow (Ammodramus bairdii) relative abundance declined with increasing stocking rates. Chestnut-collared longspur (Calcarius ornatus) relative abundance increased only at higher stocking rates indicating a possible threshold effect. Savannah sparrow (Passerculus sandwichensis) relative abundance decreased with stocking rates above 0.4 AUM after a year of grazing. Sprague’s pipit (Anthus spragueii) relative abundance declined with grazing, but the effect was weak and only significant in one year. Western meadowlark (Sturnella neglecta) abundance was unaffected by grazing. Stocking rates may be used to benefit grassland songbirds and may alter avian communities after as little as one month of livestock grazing. Applying a range of stocking rates regionally may provide habitat for many species.
Open Access
Measuring habitat fragmentation: An evaluation of landscape pattern metrics
(Wiley, 2014) Wang, Xianli; Blanchet, F. Guillaume; Koper, Nicola
Landscape patterns influence a range of ecological processes at multiple spatial scales. Landscape pattern metrics are often used to study the patterns that result from the linear and nonlinear interactions between spatial aggregation and abundance of habitat. However, many class-level pattern metrics are highly correlated with habitat abundance, making the use of these metrics as a measure of habitat fragmentation problematic. We argue that a class-level pattern metric should be (1) able to differentiate landscapes across a range of spatial aggregations, and (2) independent of habitat abundance. Based on these criteria and using both simulated and actual landscapes, we evaluated 64 class-level pattern metrics. These metrics were reclassified into four groups based on their correlation with aggregation and abundance. Among all these metrics, nine were considered robust for fragmentation measurements, which cover most of the characteristics that define pattern, including core area, shape, proximity / isolation, contrast, and contagion / interspersion.

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