I am an Ecologist with a passion for grasslands. Within that context my interests are diverse. I have worked on projects spanning the range of birds, butterflies, elephants, plants and carbon.
Skills and Expertise
Research Items (31)
- Oct 2018
Populations of grassland songbirds continue to decline, and grasslands devoted to conservation are rare across the Great Plains. To gain the most value from grasslands for grassland birds, we must understand what types of management benefit these species. We evaluated the relative abundance of grassland birds on ownership types and the association of different land use activities with their abundance. We surveyed a wide range of grasslands (e.g., from idle to heavily managed, from remnant prairie to reconstructed) across western Minnesota and northwestern Iowa, USA, in 2013 and 2014. Sites surveyed covered a gradient of landscape context, management history (fire, grazing, reconstruction), and public and private ownership. We evaluated the influence of ownership and management history on the abundance of 12 species of grassland birds by comparing Akaike's Information Criterion values of linear models that included the variables of interest to models that included only local and landscape habitat factors. Ownership explained additional variation in bird abundance beyond local and landscape variables for 7 of the 12 species, and 5 species were more common on private lands. Fire or grazing history explained variation in bird abundance for 11 species, and 7 species had greater abundance on remnant prairie than on reconstructed grassland. For all but 1 species, ownership and management factors significantly improved models above a base model of local and landscape variables typically used to predict abundance. Our results suggest remnant prairie plays an important role for grassland birds, and that grazing could be a tool to increase abundance of some grassland bird species in the region. Furthermore, tracking management history of public lands in a consistent and accessible way could help improve landscape-based models for these species.
- Mar 2018
The thousands of hectares of prairie reconstructed each year in the tallgrass prairie biome can provide a valuable resource for evaluation of seed mixes, planting methods, and post-planting management if methods used and resulting characteristics of the prairies are recorded and compiled in a publicly accessible database. The objective of this study was to evaluate the use of such data to understand the outcomes of reconstructions over a 10-year period at two U.S. Fish and Wildlife Service refuges. Variables included number of species planted, seed source (combine-harvest or combine-harvest plus hand-collected), fire history, and planting method and season. In 2015 we surveyed vegetation on 81 reconstructions and calculated proportion of planted species observed; introduced species richness; native species richness, evenness and diversity; and mean coefficient of conservatism. We conducted exploratory analyses to learn how implied communities based on seed mix compared with observed vegetation; which seeding or management variables were influential in the outcome of the reconstructions; and consistency of responses between the two refuges. Insights from this analysis include: 1) proportion of planted species observed in 2015 declined as planted richness increased, but lack of data on seeding rate per species limited conclusions about value of added species; 2) differing responses to seeding and management between the two refuges suggest the importance of geographic variability that could be addressed using a public database; and 3) variables such as fire history are difficult to quantify consistently and should be carefully evaluated in the context of a public data repository. © 2018 by the Board of Regents of the University of Wisconsin System.
In the prairies of North America, remnant native grasslands are threatened by continuing agricultural ex-tensification. Fragmentation of the remaining grassland isolates patches and limits the potential for dispersal of native species. We explored these impacts by analyzing the spatial pattern of native grassland habitats in the Prairie Coteau region of eastern South Dakota and western Minnesota, USA. Undisturbed grasslands were mapped using a GIS database of land use history combined with manual interpretation of high-resolution aerial photographs. Network analysis based on graph theory was used to examine how connectivity changed depending on the potential movement distances of organisms and to identify important patches that made large contributions to connectivity throughout the broader network. Interpatch movement was assessed using Euclidian distance as well as cost-weighted distance that assigned lower movement cost to grasslands than to human-modified land cover types. Much of the undisturbed grassland was concentrated in a single large cluster, which was connected to other habitat concentrations via corridors of "stepping stone" patches. A small number of "keystone patches", whose loss would have a disproportionately large effect on overall connectivity, were also identified. The locations of the major corridors were relatively consistent across different movement distances. Information about patch-level importance for overall network connectivity should be taken into account when prioritizing conservation and restoration. Future studies can build on this research by conducting more detailed assessments focused on particular species of concern and portions of the study area where connectivity is most limited.
Protection of lands threatened with conversion to agriculture can reduce carbon emissions. Until recently, most climate change mitigation incentive programs for avoided conversion have focused on forested ecosystems. We applied the Avoided Conversion of Grasslands and Shrublands v.1.0 (ACoGS) methodology now available through the American Carbon Registry to a threatened region of grasslands in the northern Great Plains. For all soil types across 14 counties in North and South Dakota, we used the DAYCENT model calibrated to the study area to quantify the difference in CO2 and N2O emissions under a cropping and a protection scenario, and we used formulas in the ACoGS methodology to calculate CH4 emissions from enteric fermentation under the protection scenario. We mapped the resulting GHG emissions across the entire project area. Emissions averaged 51.6 tCO2e/ha over 20 years, and with a 31% reduction for leakage and uncertainty from the ACoGS methodology, carbon offsets averaged 35.6 tCO2e/ha over 20 years. Protection of 10% of the 2.1 million unprotected ha in the project area with the highest emissions would reduce emissions by 11.7 million tCO2e over 20 years (11% of the total emissions from all unprotected grassland) and avoid a social cost of $430 million worth of CO2 emissions. These results suggest that carbon offsets generated from avoided conversion of grasslands can meaningfully contribute to climate mitigation and grassland conservation objectives.
Interseeding is a common method used to increase species richness within established reconstructed grasslands. This process depends upon the ability of the practitioner to produce resource conditions that facilitate seedling emergence in systems where such emergence is often limited. We tested effects of a mowing disturbance on interseeding success by seeding a mix of 10 common tallgrass prairie species into 1-m2 plots within two warm-season grass dominated grasslands. We clipped the vegetation on a subset of the plots once or repeatedly and measured environmental variables including litter depth, soil surface light, soil moisture, and soil nitrate within the first growing season. While clipping consistently increased soil surface light, seeded species emergence varied in response to measured environmental resources between sites. In the lowland site, emergence over two growing seasons was primarily explained by microsite and early season light availability. In the more recently burned upland site, emergence was primarily limited by later season light conditions associated with clipping. Despite this variation, seed additions increased plot-scale species richness irrespective of clipping effects mainly as a result of high establishment of wild bergamot (Monarda fistulosa) in both sites. It appears that effects of season-long defoliation management on seedling emergence depend on microsite conditions at seeding and we conclude that soil surface and established vegetation management are necessary when interseeding to increase grassland species richness. © 2016 by the Board of Regents of the University of Wisconsin System.
- Mar 2016
With the loss of over 70% of North America's grasslands (Samson et al. 2004), grassland birds increasingly rely on habitat that is privately owned and managed for livestock production. Therefore, it is critical to understand how livestock grazing influences grassland bird abundance and community structure. We evaluated the response of 4 obligate grassland bird species to grazing intensity, vegetation structure, ecological site description, and burning across a landscape including pastures with no recent grazing to pastures experiencing grazing intensities similar to that for private livestock production operations. We evaluated models using a binomial N-mixture model implemented in the R package unmarked. Overall, 3 of the 4 obligate species included positive relationships with grazing intensity in the top abundance model (i.e., grasshopper sparrow [Ammodramus savannarum], bobolink [Dolichonyx oryzivorus], and upland sandpiper [Bartramia longicauda]), suggesting the range of grazing intensities evaluated (0–4.57 animal months/ha) did not negatively affect the abundance of these species. Marbled godwit (Limosa fedoa) abundance, however, was higher with greater variability in litter depth but was not directly related to grazing intensity. Finally, the effect of year was correlated with decreasing precipitation over the course of the study and had the greatest influence on community composition with some community separation by grazing intensity. Our results suggest that cattle grazing can positively influence the abundance of some grassland bird species but annual variation in weather patterns can influence community composition at sites regardless of management decisions.
Grassland bird habitat has declined substantially in the United States. Remaining grasslands are increasingly fragmented, mostly privately owned, and vary greatly in terms of habitat quality and protection status. A coordinated strategic response for grassland bird conservation is difficult, largely due to the scope and complexity of the problem, further compounded by biological, sociological, and economic uncertainties. We describe the results from a collaborative Structured Decision Making (SDM) workshop focused on linking social and economic drivers of landscape change to grassland bird population outcomes. We identified and evaluated alternative strategies for grassland bird conservation using a series of rapid prototype models. We modeled change in grassland and agriculture cover in hypothetical landscapes resulting from different landowner decisions in response to alternative socio-economic conservation policy decisions. Resulting changes in land cover at all three stages of the annual cycle (breeding, wintering, and migration) were used to estimate changes in grassland bird populations. Our results suggest that successful grassland bird conservation may depend upon linkages with ecosystem services on working agricultural lands and grassland-based marketing campaigns to engage the public. With further development, spatial models that link landowner decisions with biological outcomes can be essential tools for making conservation policy decisions. A coordinated non-traditional partnership will likely be necessary to clearly understand and systematically respond to the many conservation challenges facing grassland birds.
- Jun 2014
Litter-removing disturbances such as fire in grasslands temporarily increase available resources for plants, opening a window of opportunity for new establishment as communities recover. At this time, new individuals or species could be added to the community as a result of germination from the local seed bank. In reconstructed grasslands this may be problematic, as the seed bank may contain a suite of undesired species reflective of prior and surrounding land uses. In two, 25-year-old, low-diversity reconstructed grasslands, we tested the effect of local seed bank establishment following litter-removing disturbance using seedling removal plots (1 m2) and plots where natural seedling establishment was allowed. Following disturbance, the vegetation was either left intact or hayed to enhance seedling establishment (a common practice following inter-seeding efforts). Although the seed bank and seedling community were dominated by resident grasses (Andropogon gerardii and Poa pratensis), recruitment from the seed bank increased species richness and reduced evenness through the addition of forb species (including Cirsium arvense) in one of the study sites. Haying temporarily altered the abundances of the dominant grasses, but did not consistently affect seedling recruitment. Disturbances that facilitate seed bank recruitment may promote establishment of undesired species within reconstructed grassland communities, and we need to take steps to better manage the contributions into and recruitment from the seed bank to reconstruct sustainable grasslands.
- Aug 2013
- 98th ESA Annual Convention 2013
Background/Question/Methods Grassland songbird populations are in decline across the tallgrass prairie. Loss of habitat is considered the primary cause, and much of the remaining grassland is in private ownership, where cattle grazing is common. The objective of this study was to evaluate the influence of grazing intensity on songbird occupancy of grasslands in a cattle-dominated landscape. The study took place in southeastern North Dakota on The Nature Conservancy’s (TNC) Brown Ranch preserve and the U. S. Forest Service’s Sheyenne National Grasslands. TNC recently reduced the grazing intensity on Brown Ranch, allowing for a comparison with the higher grazing intensity experienced on the National Grasslands. We used point counts to survey songbirds on six TNC pastures and five Forest Service pastures, and we used modified belt transects to measure vegetation structure. We used the program PRESENCE to run occupancy models for four species of grassland songbird, grasshopper sparrow (Ammodramus savannarum), bobolink (Dolichonyx oryzivorus), marbled godwit (Limosa fedoa) and upland sandpiper (Bartramia longicauda). We evaluated the influence of grazing intensity, measured in animal months per acre (AM), and structural vegetation characteristics on occupancy and detection probabilities. Results/Conclusions Preliminary results from the first two years of the study varied by species. For all species, detection probability was influenced by vegetation height and varied by visit throughout the season. For all species but the bobolink, detection probability was lower at sites with taller vegetation. Models for the upland sandpiper, marbled godwit and bobolink showed some support for the influence of grazing intensity on site occupancy. Upland sandpiper and marbled godwit occupancy increased with grazing intensity, whereas bobolink occupancy decreased as grazing intensity increased. The best-supported model for the grasshopper sparrow included a positive relationship with grazing intensity as well as vegetation density. With the exception of the grasshopper sparrow, model results were generally consistent with habitat preferences for these species, upland sandpipers and marbled godwits prefer the shorter stature vegetation created by higher grazing intensities while bobolinks prefer the denser vegetation structure created by lower intensity grazing.
- Jun 2013
Biodiversity conservation strategies are increasingly focused on regions outside national protected areas, where animals face numerous anthropogenic threats and must coexist with human settlements, livestock, and agriculture. The effects of these potential threats are not always clear, but they could have profound implications for population viability. We used savannah elephants (Loxodonta africana) as a case study to assess the physiological stress associated with living in a human-livestock-dominated landscape. We collected samples over two 3-month periods in 2007 and 2008. We used fecal DNA to identify 96 individual elephants in a community conservation area (CCA) and measured fecal glucocorticoid metabolite (FGM) concentrations as a proxy for stress. The CCA is community Maasai land managed for livestock and wildlife. We compared the FGM concentrations from the CCA to FGM concentrations of 40 elephants in Amboseli National Park and 32 elephants in the Maasai Mara National Reserve, where human settlements and intense livestock grazing were absent. In the CCA, we found no significant individual differences in FGM concentrations among the elephants in 2007 (p = 0.312) or 2008 (p = 0.412) and no difference between years (p = 0.616). The elephants in the CCA had similar FGM concentrations to the Maasai Mara population, but Amboseli elephants had significantly lower FGM concentrations than those in either Maasai Mara or the CCA (Tukey pairwise test, p < 0.001), due primarily to females excreting significantly lower FGM relative to males (p = 0.025). In the CCA, there was no relation among female group size, average pairwise group relatedness, and average group FGM concentration. We found no clear evidence of chronic stress in elephants living on CCA communal land, which is encouraging for conservation strategies promoting the protection of animals living outside protected areas. © 2013 Society for Conservation Biology No claim to original US government works.
Non-invasive DNA-based capture–mark–recapture (CMR) methods have been developed to estimate population size and other parameters and have the advantage that samples can be collected without the need to see or disturb the animals. There are, however, few comparisons of DNA-based CMR estimates of animal population size with estimates from non-genetic methods. We compared the results of a dung-density based survey of an Asian elephant (Elephas maximus) population with a simultaneous fecal DNA-based CMR survey of the same population. We found 545 dung-piles along 116 line transects, converted dung-pile density to elephant density using rates of defecation and dung disappearance, and derived a population estimate of 141 (95% CI = [95, 208]) elephants. We collected 267 fecal samples during three CMR sampling sessions: 215 (81%) yielded sufficient genotypic information for analysis and gave an estimated population size of 132 (95% CI = [120,149]) elephants, closely matching the estimate produced by the dung-density method but with greater precision. The DNA-based method also provided information on population structure. We conclude that DNA-based CMR methods provide more precise abundance estimates, and more data about population structure and dynamics, than dung density-based methods. Fecal DNA-based CMR methods also require less time in the field and can be used when dung density methods are impracticable. Finally, fecal DNA based CMR methods are now cheaper than dung density based methods when line transect survey costs are approximately equal to CMR survey costs and dung decay rate monitoring costs are greater than laboratory costs (which will usually be the case).
We investigated the genetic metapopulation structure of elephants across the trans Rift Valley region of Kenya and Tanzania, one of the remaining strongholds for savannah elephants (Loxodonata africana) in East Africa, using microsatellite and mitochondrial DNA (mtDNA) markers. We then examined this population structure to determine the source population for a recent colonization event of savannah elephants on community-owned land within the trans rift valley region. Four of the five sampled populations showed significant genetic differentiation (p<0.05) as measured with both mtDNA haplotypes and microsatellites. Only the samples from the adjacent Maasai Mara and Serengeti ecosystems showed no significant differentiation. A phylogenetic neighbour-joining tree constructed from mtDNA haplotypes detected four clades. Clade four corresponds to the F clade of previous mtDNA studies that reported to have originated in forest elephants (Loxodonta cyclotis) but to also be present in some savannah elephant populations. The split between clade four and the other three clades corresponded strongly to the geographic distribution of mtDNA haplotypes across the rift valley in the study area. Clade four was the dominant clade detected on the west side of the rift valley with rare occurrences on the east side. Finally, the strong patterns of population differentiation clearly indicated that the recent colonists to the community-owned land in Kenya came from the west side of the rift valley. Our results indicate strong female philopatry within the isolated populations of the trans rift valley region, with gene flow primarily mediated via male movements. The recent colonization event from Maasai Mara or Serengeti suggests there is hope for maintaining connectivity and population viability outside formal protected areas in the region.
Map of the sample locations and groupings in Serengeti National Park, Tanzania for testing within park FST structure using mtDNA haplotypes; names correspond to the southern (SSE), central (CSE), western (WSE) and northern (NSE) groupings. (TIF)
Barplots from STRUCTURE using LOCPRIOR depicting population assignment for individuals mapped and sorted by sampling location for K = 2 though K = 5: Amboseli (AM), Community Conservation Area (CCA), Maasai Mara (MM), Serengeti (SE) and Tarangire (TA); the Rift Valley splits the study area, Maasai Mara and Serengeti are on the west side of the valley, Amboseli and Tarangire are on the east side of the valley while the CCA is located within the Rift Valley. (TIF)
Large tracts (>1000 ha) of prairie are essential to the sustainability of grassland ecosystem services, yet in many ecoregions only small fragments remain. Glacial Ridge is among the largest prairie-wetland restorations ever attempted. Started in 2000, the 9000 ha project in northwest Minnesota, USA, was initiated to reconnect 14 small tallgrass prairie remnants. In all, 15,200 ha of contiguous habitat comprise the project's direct accomplishment. We created a partnership of more than 30 organizations, filled 177 km of drainage ditch, restored 1240 ha of wetland, and replanted 8100 ha. Flooding has been mitigated, water quality improved, and native vegetation reestablished. Animals not documented for decades have again occupied the site. Despite these accomplishments, the project would have been unnecessary if the land had been purchased in the 1970s, prior to conversion to agriculture, at one-tenth the restoration cost. Our challenges related to funding, differences in partners' restoration philosophy, community concerns about floods and tax losses, difficulties in obtaining seed, and follow-up management of invasive weeds. We summarize the restoration process and share basic principles that will help others to develop large-scale prairie restoration projects in the future.
- Oct 2012
Aim Dispersal is a critical component of animal ecology that is poorly understood for most species. In particular, savanna elephants (Loxodonta africana) have been studied for decades in national parks across Africa, but little is known about their dispersal into new or unused habitats or their population dynamics in human-dominated landscapes. We capitalized on a natural dispersal event of savanna elephants recolonizing communal land in southern Kenya to document their demographic characteristics and genetic relationships. Location Rift Valley province of Kenya. Methods We collected faecal samples and used genetic methods to identify individuals, estimate the sex ratio and evaluate the patterns of relatedness within the female groups and male aggregations. We also measured dung bolus circumference to assign age classes to individuals and estimate the age structure. Results We identified 112 individuals with a sex ratio not different from one (1.32:1.00). The age structure was skewed towards younger elephants (71%), suggesting the potential for rapid growth from reproduction. We detected significantly higher kinship levels within female groups (R = 0.124 ± 0.023), suggesting that family groups colonized the site, but found little support for higher-order genetic relationships among female groups. Males detected together were unrelated (R = 0.003 ± 0.030). Main conclusions Our results suggest that highly social mammals, such as savanna elephants, disperse into unoccupied habitat as family groups and that a young demographic structure and a large number of males might be expected in establishing populations. These findings highlight the potential value of indirect, non-invasive methods for assessing elephant herd and demographic characteristics when direct observations are difficult.
- Aug 2012
- 97th ESA Annual Convention 2012
Background/Question/Methods The recovery after a disturbance in tallgrass prairies can be driven by either seed or vegetative regeneration. At remnant tallgrass prairies, recovery is dominated by vegetative regrowth. At established reconstructed prairies, seeds may or may not play a role in recovery. Disturbance is expected to increase the resources available to seedlings at both types of prairies, but it is not clear how much disturbance is required and what resource is most important. We asked whether seeds, either added or those present in the seed bank, contribute to diversity following disturbance, and whether their contribution changes with disturbance frequency. We tested that question at two 25-year-old, low diversity reconstructed prairies dominated by Andropogon gerardii. After a fire or litter removal in spring 2011, we established treatments to compare the diversity among 1 m2plots with either all seedlings from the seed bank removed, seed bank seedlings allowed (control), or seeds added. Each type of seed treatment was then clipped zero, one, or three times during the first growing season. At four microsites within each plot, we measured available light, soil moisture, and nitrate against seedling abundance to determine the mechanism that links disturbance to seedling establishment. Results/Conclusions Germination tests indicated that the seed bank contained only seven species at one site and eleven species at the second site and non-native species comprised 97% of all seeds. After one growing season, seedlings of eight species from the seed bank were present and seven of the ten added species were present. At both sites, more frequent clipping increased light availability, but did not alter available water and nitrate. Effects of these resources on seedling abundance were site and weather dependent. At the first site, which received above-average precipitation, seedlings were more abundant in microsites with lower soil moisture and nitrate levels. The second site received below-average precipitation and seedlings were more abundant in microsites with less light. Although seeds originating from the seed bank and from the added seed mix germinated, neither contributed to plot-scale diversity at the end of the first growing season. This suggests that once established, reconstructions are also primarily maintained by vegetative regeneration. Furthermore, given the high-proportion of non-native species in the seed bank, if managers attempt to increase local diversity through seed addition and management for seedling establishment, that management may lead to increased invasive species cover.
The Lao People’s Democratic Republic (PDR) may have the largest Asian elephant population in Indochina. However, elephants on Lao PDR’s Nakai Plateau are potentially threatened by the construction of a hydropower dam that will flood important habitat. We conducted a non-invasive genetic study of elephants in this region to provide baseline data on genetic diversity and social structure prior to dam construction. For the 102 elephants we detected, values of observed heterozygosity (0.711) and allelic diversity (8.0 alleles/locus) at microsatellite loci were higher than those found in elephant populations in India and Vietnam, while mitochondrial diversity (haplotype diversity 0.741; nucleotide diversity 0.011) was similar to that reported for the Lao/Vietnam region. Six mitochondrial haplotypes were detected, representing both major clades previously reported in this species. Relatedness estimates between females and young detected near each other are consistent with familial relationships, and relatedness estimates between adult males and females suggest male locational dispersal. Since family group structure appears to be intact in the Nakai region, these elephants will likely move as relatively large family groups in response to habitat disturbance. These results have positive implications for the viability of the elephant population in this region, demonstrate its conservation significance, and will be valuable for predicting and monitoring the effects of the hydropower dam over time. KeywordsAsian mammals– Elephas maximus –Dispersal–Microsatellites–Relatedness
- Jun 2011
We report the development of a reliable and efficient method for molecular sexing of all extant elephant taxa. We developed primers that amplify two short Y-specific fragments (SRY1 and AMELY2) and one longer X-specific fragment (PLP1), developed from elephant sequences in one multiplex PCR. All fragments were designed to be short (< 200 basepairs) for use with degraded DNA and to be 50 basepairs apart to optimize visualization on agarose gels or as electropherograms. The multiplex PCR method matched sexes for at least 97.9% of the noninvasive savannah elephant samples and produced the expected female/male banding patterns for 14 African forest and 11 Asian elephant samples. We found this method to be more robust, efficient and less prone to contamination than previously developed sexing methods for elephants.
- Dec 2010
Crop raiding is one of the most common forms of human–elephant conflict. Deterring elephants from raiding crops requires an understanding of the factors influencing the behavior of the individuals involved. We collected fecal samples from five group ranches in southern Kenya where crop-raiding incidents had occurred (n=10) and two protected areas, Amboseli National Park (n=24) and Maasai Mara National Reserve (n=20). We used molecular sexing to sex the individuals and radioimmunoassay kits to determine the level of glucocorticoid metabolites (i.e. stress hormones) in their dung. All crop-raiding individuals were male and had a significantly elevated concentration of glucocorticoid metabolites as compared with the Amboseli elephants (W=12, P=0.0005). We detected no significant difference between Maasai Mara elephants and either Amboseli or the crop-raiding elephants when just males were compared. Our results suggest that crop raiding may be related to stress in elephants.
Se ha confirmado mediante numerosos estudios que las aves pueden utilizar información social adquirida mediante la observación de otros individuos al seleccionar el hábitat y muchos aspectos de esta información social pueden emplearse para manejar las poblaciones de aves. Las implicaciones de la atracción entre individuos coespecificos para la conservación son especialmente promisorias para el manejo y a medida que la investigación progresa es importante considerar cómo se puede aplicar este comportamiento a la conservación en la práctica. Las bases biológicas de la atracción entre individuos coespecíficos y las repercusiones de manipular la distribución de las especies mediante métodos de atracción no se entienden adecuadamente, pero las decisiones de conservación a menudo no pueden esperar al desarrollo de investigaciones científicas. En este trabajo, sintetizamos la investigación actual sobre la manipulación de aves canoras mediante métodos de atracción de individuos coespecíficos y revisamos nuestros baches en el conocimiento de forma crítica. Revisamos la literatura publicada sobre experimentos de atracción de individuos coespecificos en aves canoras y encontramos que, de 24 estudios en los que éstos fueron emprendidos, 20 tuvieron éxito atrayendo a las aves. Aunque muchos experimentos han tenido éxito atrayendo individuos coespecíficos usando varias señales, esbozamos algunos asuntos que deben considerarse antes de manipular a las aves canoras mediante métodos de atracción. Además, resaltamos áreas en las que es necesario realizar investigaciones para mejorar el entendimiento de la atracción de individuos coespecíficos y su uso en conservación.
- Jan 2010
- Prairie Conservation & Endangered Species Conference
Adapting Conservation Strategies for Future Climate Change in the Tallgrass Aspen Parkland. (Poster). P. Gerla, C. Hamel, R. Reisz, M. Cornett, M. Ahlering & J. Eerkes. Page 116 in Danyluk, D. 2011. Proceedings of the 9th Prairie Conservation & Endangered Species Conference. Critical Wildlife Habitat Program, Winnipeg, MB. 212 pp.
- Oct 2009
Although critical to habitat and population management, the proximate cues that birds use to establish territories are largely unknown. Understanding these cues is important for birds, such as many grassland birds, that exhibit high annual variability in population density and make new habitat-selection decisions annually. Identifying the actual cues used is difficult in the field, but the factors associated with the arrival densities of birds can help uncover variables that are involved in or correlated with cues used for selection. During the summers of 2002–2004, we investigated how weather and local vegetation factors were related to arrival densities of Grasshopper Sparrows (Ammodramus savannarum) and Baird's Sparrows (A. bairdii) at three locations across North Dakota and Saskatchewan. Spring densities of Grasshopper Sparrows were positively correlated with concurrent May precipitation, whereas densities of Baird's Sparrows were negatively correlated with the previous winter's snowfall. We used a model-selection approach to evaluate the vegetation characteristics associated with arrival densities of birds. Grasshopper Sparrow densities showed a strong negative relationship to woody cover, and Baird's Sparrow densities showed a negative relationship to vegetation height and vegetation density near the ground. Our results provide a first detailed look at habitat and weather associations immediately after arrival in spring and an important first step in uncovering factors that may be involved in habitat selection in two grassland species.
- Sep 2006
Territorial songbirds generally use song to defend territories and attract mates, but conspecific song may also serve as a cue to attract other male songbirds to a breeding site. Although known to occur in some colonial and forest-associated species, only recently have investigators examined conspecific attraction in grassland species. We used a playback experiment to examine the possible role of conspecific attraction for males searching for potentially suitable breeding habitat in a grassland specialist, the Baird's Sparrow (Ammodramus bairdii). Experimental playback plots and control plots with similar landscape and vegetation characteristics were established at two sites in North Dakota. Baird's Sparrows colonized three of six experimental plots and none of six control plots. Males on experimental plots established territories adjacent to the playback stations and were sometimes observed counter-singing with the playback of conspecific songs. Vegetation characteristics were similar on all study plots, and did not explain differences in bird density on our treatment plots. Although we found that playback of conspecific songs attracted male Baird's Sparrows to previously unoccupied, potentially suitable habitat, further experiments are needed to examine the importance of conspecific attraction relative to other cues that birds may use, such as vegetation features. The conservation and management implications of conspecific attraction are not completely understood, but the presence of conspecifics should be considered as a potential cue in habitat selection by all species of birds.
- Dec 2005
Typescript. Thesis (Ph.D.)--University of Missouri-Columbia, 2005. Vita. Includes bibliographical references.
A recent review of published studies revealed that predators generally have lower population densities than non-predators in a variety of communities. We report here similar results for a highly replicated study of macroinvertebrates that colonized very uniform detrital microcosms in an old field. This pattern persisted even though predators usually were smaller than non-predators, as determined by body length and volume.