Mountain Scholar :: Browsing by Author "Pejchar, Liba, advisor"

Browsing by Author "Pejchar, Liba, advisor"

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Open Access
Advancing the science and practice of conserving hihiwai: using ecology and traditional ecological knowledge to identify and overcome threats to an endemic Hawaiian gastropod
(Colorado State University. Libraries, 2021) Ka'awa-Gonzales, Kiloaulani E. C., author; Pejchar, Liba, advisor; Clements, William H., advisor; Niemiec, Rebecca, committee member
Aquatic gastropods are valuable indicators of stream health in tropical ecosystems globally. Sustaining gastropods on islands is particularly important because these species provide numerous ecosystem services such as water purification, nutrient cycling, mediating the transfer of carbon through food webs, and providing sustenance for people. Hihiwai (Neritina granosa) is an amphidromous snail that was used as a subsistence food source in ancient times by Native Hawaiians and is still harvested today. Yet, this species is of conservation concern and both the ecological factors associated with its density and distribution as well as the socio-cultural knowledge associated with this species are largely unknown. Bridging Traditional Ecological Knowledge (TEK) and western science, which requires valuing indigenous knowledge and leadership and incorporating these ways of knowing into conservation science and practice, is an effective strategy to address this paucity of information in local and Indigenous communities. TEK is particularly important on islands where indigenous communities steward their often imperiled cultural and natural heritage. Evaluating the factors contributing to hihiwai loss and recovery using a combination of western science and TEK could serve as a model for Indigenous and local communities at the marine/freshwater interface globally. To address these knowledge gaps, I surveyed four streams on the Hawaiian Islands of Molokai and Maui to 1) determine which characteristics of stream systems are associated with Hihiwai population density across age classes, and 2) evaluate the size distribution of adult hihiwai as a function of stream characteristics. Specifically, I used stratified random quadrat sampling to assess hihiwai densities along an elevational gradient in streams with (n = 2) and without (n = 2) diversions. I collected data on stream characteristics such as width, depth, velocity, discharge, temperature, shading, and substrate. I found that hihiwai recruits, juveniles and adults were more abundant in diverted streams, all size classes and adult length were positively associated with stream depth, adult hihiwai were more likely to occur at higher elevations, and there was an inverse relationship between adult size and density, with larger hihiwai more likely to occur where adults were least abundant. In parallel with the stream surveys, I conducted semi-structured interviews with 20 local community members on Molokai to examine how traditional ecological knowledge and local experience can be used to better understand the ecology and cultural value of hihiwai, and to engage local communities in the conservation of this species and its habitat. Three major takeaways were identified as relevant for understanding the drivers, impacts, and next steps for hihiwai conservation: 1) community members believe that hihiwai populations are decreasing due to a combination of direct (overharvesting, water diversions) and indirect (higher stream temperatures, invasive plants) anthropogenic effects; 2) The perceived decrease in hihiwai abundance on Molokai has resulted in fewer opportunities for local people to connect with each other and spend quality time (eating and picking hihiwai), a loss of historic knowledge of hihiwai and cultural identity, and has disrupted the transmission of cultural and ecological knowledge to the next generation; and (3) Community members emphasized the need for informed local conservation leaders who represent the interests of the local Molokai people to guide and enforce hihiwai and Hawaiian stream management. Although community perceptions of whether bottom-up or top-down management strategies would be more effective were mixed, there is a general consensus that a change in values toward hihiwai harvest and possible harvest limits are needed to ensure healthy hihiwai populations in the future. My findings from this cross disciplinary study highlight the overlap, as well as the novel information that can emerge from integrating ecological and social research. Bridging the gap between western ecological science and TEK through local community collaboration will be critical for developing effective management plans that ensure ecological and cultural sustainability of hihiwai in Hawaii.
Open Access
An introduced plant affects the structure and function of riparian food webs
(Colorado State University. Libraries, 2017) Riedl, Hannah, author; Clements, William, advisor; Pejchar, Liba, advisor; Kondratieff, Boris, committee member; Fausch, Kurt, committee member
Aquatic and terrestrial ecosystems are closely linked by the reciprocal flux of resource subsidies, but these dynamics can be uncoupled by anthropogenic change. Introduced species are easily spread by riverine systems, but the effects of non-native riparian vegetation on reciprocal arthropod subsidies are essentially unknown. I studied the aquatic and terrestrial arthropod communities, and their flux into and out of the stream channel, in stream reaches in northwestern Colorado invaded and uninvaded by New Mexico locust (Robinia neomexicana A. Gray), a woody plant north of its native range. I also evaluated whether the aquatic- and terrestrial-derived diets of riparian songbirds were altered in stream reaches with New Mexico locust. I found that reaches with New Mexico locust had fewer terrestrial arthropods collected from vegetation, particularly in spring. Consistent with these results, some songbird species using invaded sites displayed diet shifts towards aquatic-derived resources. Aquatic resources comprised approximately 34% of the songbird assemblage's diet, which highlights the importance of aquatic subsidies to riparian consumers. In contrast, there were no impacts of New Mexico locust on the aquatic insect community associated with the invasion. Overall, seasonal and annual variation best described patterns of arthropod subsidy production and consumption. Since locust invasion did not drive strong patterns in insect communities, and because seasonal and annual factors provide little information about environmental drivers of resource subsidies, we also assessed the importance of vegetation and stream characteristics on aquatic and terrestrial arthropod communities. I found terrestrial insect biomass and richness increased with percent ground cover, forb cover, and vertical vegetation structure, and decreased with percent cover of New Mexico locust. Interestingly, vegetation characteristics best described emergence patterns of adult aquatic insects, but stream characteristics best described larval aquatic insect patterns. Our results support the use of a multi-functional approach to assessing ecosystem alteration. By evaluating the multiple pathways through which a non-native species can affect riparian systems, I found a close connection between stream and riparian ecosystems. I found the impacts of invasion were most apparent for arthropod metrics directly related to vegetation (i.e., arthropods collected from foliage), with weaker responses for indirect metrics (i.e., aquatic insect biomass, songbird diet components).
Open Access
Assessing bird-mediated ecosystem services and disservices in Colorado apple orchards
(Colorado State University. Libraries, 2016) Mangan, Anna Mattern, author; Pejchar, Liba, advisor; Werner, Scott J., committee member; Kendall, William, committee member; Ode, Paul, committee member
Agriculture provides food, fuel and fiber to our growing human population and as the largest terrestrial biomes, crop and pastureland are major drivers of land use change. Small organic farms have the potential to provide habitat for biodiversity while also contributing to food security. My research examined the characteristics of organic apple orchards associated with habitat use of human-adapted and human-sensitive birds as well as how birds influence fruit production positively through insect pest control and negatively through fruit damage. I used a stratified study design to survey birds, observe bird frugivory, capture birds to collect and analyze avian fecal samples, and assess bird and insect damage with an exclosure experiment in small organic farms in western Colorado. I calculated species richness and community similarity among apple blocks and adjacent habitat and evaluated bird habitat use as a function of orchard characteristics (i.e., location in orchard, size of apple block or edge-to-area ratio). I calculated the proportion of bird observations associated with apple frugivory and the proportion of fecal samples that were positive for codling moth DNA to identify bird species that could affect production. I compared bird damage to apples as a function of orchard characteristics and investigated factors that influenced codling moth damage, including access to fruit and moths by birds. I found that organic apple orchards in this region provided habitat for 42 human-adapted and 27 human-sensitive bird species and the bird community in orchards was relatively similar to shrub/tree habitat adjacent to apple blocks. There was sufficient data to model habitat use by seven species; however, use did not vary as a function of the orchard characteristics I measured. Similarly, apple damage by birds and codling moths was consistent within and across apple blocks that varied in size and variety. However, codling moth damage was negatively associated with the exclusion of birds. The molecular technique used to detect codling moth DNA in fecal samples was successful and one species (brown-headed cowbird) had fecal samples positive for codling moth DNA. Five species of birds (Bullock's oriole, common raven, house finch, Lewis's woodpecker, and western scrub-jay) were observed foraging on apples. However, the effect of birds as either agents of fruit damage or pest control in this agroecosystem appeared rather minor. These results demonstrate that organic apple orchards have the potential to provide habitat for diverse bird communities, including species typically sensitive to human activities. Further, because rates of bird-induced fruit damage were low and attributed to a small subset of the avian community, these agroecosystems may provide bird habitat without compromising production.
Open Access
Bird and mammal response to large-scale habitat mitigation for game species in the oil and gas fields of northwest Colorado
(Colorado State University. Libraries, 2016) Gallo, H. Travis, author; Pejchar, Liba, advisor; Noon, Barry, committee member; Paschke, Mark, committee member; Wittemyer, George, committee member
To view the abstract, please see the full text of the document.
Open Access
Ecological and social consequences of collaborative bison reintroduction in the western U.S.
(Colorado State University. Libraries, 2018) Wilkins, Katherine DeWitt, author; Pejchar, Liba, advisor; Knapp, Alan, committee member; Garvoille, Rebecca, committee member; Knight, Rick, committee member
Collaborative conservation has been underway for centuries in diverse communities across the globe. More recently, collaborative groups of private and public land managers have coalesced around common natural resource objectives in the United States. This dissertation advances the science and practice of collaborative conservation through a literature review and two highly collaborative projects on bison reintroduction in the western United States. My specific objectives are: 1) To evaluate the status and impact of collaborative conservation groups in the United States; 2) To assess the ecological consequences of bison reintroduction for birds, mammals, and plants in Colorado's shortgrass prairie; 3) To understand how bison reintroduction affects human connections to grassland landscapes; and 4) To compare the effects of bison and cattle grazing on birds and plants in Colorado and New Mexico. To evaluate the status of U.S.-based collaborative conservation groups, I conducted a literature review to identify what factors motivate group formation, and to quantify biophysical, social, and economic goals, actions to achieve those goals and outcomes, and how outcomes were assessed. I also characterized the geographic distribution, participants and funding sources of U.S.-based collaborative conservation groups. To accomplish these objectives, I searched for peer-reviewed journal articles, book chapters, and reports in online databases, resulting in 174 papers that described 257 collaborative conservation groups in all 50 states. Overall, information on outcomes and how groups assessed outcomes was sparse. For those groups with published outcomes, most outcomes had positive results for biophysical, social, and economic goals. To assess the ecological consequences of species reintroduction and how reintroductions may catalyze public engagement in grassland conservation, I assessed both the ecological and social effects of bison reintroduction to northern Colorado. Specifically, I explored the effect of bison reintroduction on: 1) bird density and habitat use, 2) mammal habitat use, 3) vegetation composition and structure, and 4) human connections (place attachment) to a shortgrass prairie. To measure ecological responses, I surveyed birds, mammals, and plants before and after bison reintroduction. To understand how bison shape visitor connections to grasslands, I gave structured surveys to people who visited the site before and after bison reintroduction. I found few short-term effects of bison on grassland birds, mammals, and plants. However, I measured a significant increase in place attachment to the grassland site post reintroduction. These results suggest that bison reintroduction does not have strong, short-term ecological effects, but does have immediate, positive benefits for connecting people to ecosystems. I recommend that future projects prioritize monitoring ecological and social outcomes to advance the science and practice of bison reintroduction. To understand whether non-native species can serve as proxies for extinct or rare native species, I evaluated the role of bison and cattle grazing in shaping habitat for grassland birds and plants. To compare ecological responses, I surveyed birds and plants between bison, cattle, and reference sites in Colorado and New Mexico. While I found few differences in plant height and cover among bison, cattle, and reference sites, I did find significant differences in bird densities among the sites. In both Colorado and New Mexico, some grassland obligate birds preferred bison sites, while others preferred cattle sites. Bison and cattle may serve as reciprocal ecological surrogates in cases where they have similar densities on the landscape, where cattle graze on a rotational system. Overall, my dissertation demonstrates that collaborative conservation often achieves success, but these outcomes are not always assessed or reported. I also show that a highly collaborative bison reintroduction effort in Colorado had few ecological effects in the short-term, but did help connect people to a grassland landscape. In addition, my study found that collaboratively managed bison and cattle herds in Colorado and New Mexico create viable habitat for obligate grassland birds.
Open Access
Effects of a non-lethal chemical repellent on airport bird communities
(Colorado State University. Libraries, 2024) Urchek, Kathleen, author; Pejchar, Liba, advisor; Werner, Scott, committee member; Kendall, William, committee member; Bright, Alan, committee member
Human-wildlife conflicts are likely to occur wherever the interests and activities of humans and wildlife overlap. Airport environments are a prime example of where such conflict is pervasive because wildlife can view airports as habitat, yet the presence of wildlife increases the risk of collision. As humans increase our reliance on air travel and development encroaches on natural areas, conflicts between humans and wildlife will continue to be prevalent in airport settings, thus creating the need for effective management tools. To assess the effectiveness of one such tool, we evaluated the effect of a non-lethal chemical repellent on bird abundance, species richness, movement, and behavior in airport settings. Following a Before After Control Impact Paired study design we compared the changes among each variable from a period of pre-treatment to a period of active treatment, in both treated and control sites. Using Poisson and zero-inflated mixed effects models we found that the repellent is likely effective in shifting birds from treated to untreated areas within airports, and that the abundance of two common species, Bobolinks and European Starlings, declined following treatment. We also found that the repellent does not change the frequency in which birds move out of treated plots and intersect with runways, but may be altering the within-plot behavior of Eastern Meadowlarks, Red-winged Blackbirds, and Sandhill Cranes. Our mixed findings highlight the need for continued study of the mechanisms behind avian response to chemical repellents in airport settings. Although a diverse set of approaches will always be needed to alleviate the many human-wildlife conflicts associated with airports, here we show that, to promote co-existence with wildlife, this chemical repellent can be a part of that toolset.
Open Access
Effects of an introduced tree, New Mexico locust (Robinia neomexicana), on riparian birds
(Colorado State University. Libraries, 2017) Stinson, Lani Treadway, author; Pejchar, Liba, advisor; Clements, William H., committee member; Hufbauer, Ruth A., committee member
Biological invasions are global drivers of environmental change and riparian ecosystems are particularly susceptible to the effects of non-native species. While much research has focused on understanding the impacts of non-native introductions from other biogeographic regions, effects of plant species that spread close to or within their native ranges are relatively understudied. My research investigated the effects of the near-range introduction of a non-native woody plant, New Mexico locust (Robinia neomexicana), on a variety of ecological responses within the Clear Creek drainage of northwestern Colorado, USA. I used riparian songbirds as model species to investigate invasion-mediated effects on 1) changes to avian habitat use, including species richness, occupancy, and abundance; 2) effects on songbird reproductive success, including nest survival and productivity; and 3) changes to aquatic insect subsidies and avian diet compositions. My first chapter provides a general synthesis of fitness consequences of plant invasion through a global systematic review of introduced plant effects on songbird reproductive success. Only 16% of the 137 songbird responses examined resulted in significant effects, and these were predominately negative and highly context-dependent. However, non-significant trends were much more prevalent and mixed in direction. The literature review highlighted the lack of study on fitness-level impacts of invasion, uncovered a strong geographic bias for North American studies, and identified knowledge gaps, such as the lack of studies on juvenile survival during the postfledging period. In chapter two, I examine the effects of New Mexico locust invasion on the habitat use and reproductive success of breeding songbirds in the Clear Creek drainage of northwestern Colorado. Despite evidence of biotic homogenization of the vegetation community with increasing invasion intensity, I found few negative impacts on the songbird community. Rather, the introduced locust provided quality breeding habitat to support diverse assemblages of riparian birds. Not only did I find increased bird species richness with increasing invasion intensity, but nest productivity was significantly higher in invaded habitats compared to those where locust was absent. Overall, I found that environmental characteristics other than invasion (i.e., elevation and shrub density) were more important predictors of avian habitat use. There was also no evidence of reduced nest survival in nests built in locust or in nests in native plants situated in locust-invaded habitats. My third chapter, a collaboration with Colorado State University M.S. student Hannah Riedl, uses stable isotope analysis of avian fecal samples and insect prey to investigate invasion-mediated changes in the aquatic resource subsidies provided to avian insectivores. We quantified the amount of terrestrial- and aquatic-derived insect prey consumed by a riparian songbird assemblage and assessed whether relative prey contributions differed between non-invaded reference sites and sites invaded by New Mexico locust. We found that songbird diets were comprised of approximately one third aquatic resources and two-thirds terrestrial resources, highlighting the importance of aquatic resource subsidies for riparian consumers. Although differences in diet composition between reference and locust habitats were highly species-specific and inconsistent across years, we found significant diet shifts towards more aquatic-derived prey at locust sites for two species of avian insectivores. Collectively, my findings provide little support for negative impacts on riparian bird communities associated with the near-range introduction and establishment of New Mexico locust within Clear Creek drainage. Similar or stronger effects might be expected for invasive alien species introduced from more geographically isolated native ranges. Combining multiple ecological response variables to obtain a more complete and mechanistic understanding of invasion impacts is critical for advancing invasion biology and facilitating effective conservation of native communities.
Open Access
Home range estimates, habitat selection, and nesting behavior of Ferruginous Hawks (Buteo regalis) in western Wyoming
(Colorado State University. Libraries, 2024) Ramirez, Sarah Kathleen, author; Pejchar, Liba, advisor; Koons, David, committee member; Angeloni, Lisa, committee member
Oil and gas development has the potential to negatively impact wildlife, but the consequences for some raptor species are less well understood. Ferruginous Hawks could be particularly susceptible to negative effects due to their large habitat requirements and sensitivity to anthropogenic disturbance. Given the rapid expansion of oil and gas development in many parts of the range of Ferruginous Hawks, it is critical to evaluate habitat use in both a pre-construction and post-construction environment. Understanding selection of habitat resources and nest sites, as well as the factors that contribute to home range estimates, nest success and nest productivity could help inform efforts to mitigate against potential negative effects of land use change. In my first chapter, I aimed to investigate factors associated with breeding Ferruginous Hawk home range estimates and habitat selection in a landscape slated for energy development. In a sagebrush-steppe study site in western Wyoming, I captured breeding hawks and used radio and satellite-telemetry to collect location data, estimate home range estimates, and model habitat selection. Home range estimates were smaller for females and hawks with egg-laying breeding status, and larger with increasing numbers of producing wells. Ferruginous Hawks selected habitat with high terrain ruggedness, low shrub cover, and areas closer to primary prey, and avoided areas with high density of wells. The relationship between lagomorph density and distance to development was dependent on scale. My findings show that home range estimates are smaller in my study relative to other parts of the species' range, and that future energy development is likely to reduce habitat quality and availability for Ferruginous Hawks. In my second chapter, I investigated the factors associated with nest site selection, success, and productivity in the same study site in western Wyoming. I used an existing dataset on nest site locations, nest success, and productivity, and collected new data on these response variables between 2019 and 2023. I used a resource selection function model (RSF) to evaluate nest site selection and used generalized linear mixed models (GLMMs) to evaluate nest success and productivity. Ferruginous Hawks selected nest sites in developed-open space landcover (e.g., areas cleared of vegetation with little or no infrastructure), higher topographic position index (TPI), and in closer proximity to producing wells (km). In contrast, breeding hawks avoided nest sites in areas with higher densities of producing wells (per km2) and more shrub cover (%). Nest success and productivity of egg-laying pairs was positively associated with artificial nesting platforms (ANPs) and negatively associated with anthropogenic structures and rocky outcrops, developed-open space landcover, TPI and year. These findings suggest that Ferruginous Hawks may be subject to an ecological trap when they nest on anthropogenic structures, but that ANPs are a potentially viable tool for mitigation.
Embargo
How common bird populations respond to their environment across species and scales
(Colorado State University. Libraries, 2022) Davis, Kristin Petersilia, author; Pejchar, Liba, advisor; Sofaer, Helen, committee member; Horton, Kyle, committee member; Ruegg, Kristen, committee member
To view the abstract, please see the full text of the document.
Open Access
I. Seed dispersal by the critically endangered Alala (Corvus hawaiiensis). II. Integrating community values into Alala (Corvus hawaiiensis) recovery
(Colorado State University. Libraries, 2011) Culliney, Susan Moana, author; Pejchar, Liba, advisor; Savidge, Julie, committee member; Bruyere, Brett, committee member
Species loss can lead to cascading effects on communities, including the disruption of ecological processes such as seed dispersal. The endangered Alala (Corvus hawaiiensis), the largest remaining species of native Hawaiian forest bird, was once common in mesic and dry forests on the Island of Hawaii, but today exists solely in captivity. Prior to its extinction in the wild, the Alala may have helped establish and maintain native Hawaiian forest communities by dispersing seeds of a wide variety of native plants. In the absence of Alala, the structure and composition of Hawaii's forests may be changing and some large-fruited plants may be dispersal limited, persisting primarily as ecological anachronisms. I fed captive Alala a variety of native fruits, documented behaviors relating to seed dispersal, and measured the germination success of seeds that passed through the gut of Alala relative to the germination success of seeds in control groups. Alala ate and carried fourteen native fruits and provided germination benefits to several species by ingesting their seeds. My results suggest that some plants rely heavily on Alala for these services. In captivity, juvenile birds displayed seed dispersal behaviors more often than adult birds for most fruiting plants in my study. I introduced captive Alala to two large-fruited, dry forest plants, not previously recorded as Alala food resources, but which may have once been part of their natural diet. The seed dispersal behavior that Alala displayed towards these species supports the inclusion of dry and mesic forests in Alala habitat restoration plans and adds weight to the idea that plant dispersal limitation may contribute to the rarity of these plants. My study provides evidence that Alala have the capacity to play a vital role in maintaining the diversity of fruiting plants in native Hawaiian forests through seed dispersal and enhanced seed germination, thus adding greater urgency to efforts to restore Alala to their former range. Incorporating community values and perspectives into endangered species recovery programs is generally underutilized but can be an important tool for achieving conservation success. Species recovery programs adjacent to human communities can particularly benefit from integrating local perspectives on nature into program goals and practices. The Alala or Hawaiian Crow (Corvus hawaiiensis) is currently extinct in the wild but once possessed great cultural value to ancient Hawaiians and may have played a pivotal role as a seed disperser in Hawaii's forests. Past efforts to restore this charismatic bird to its historical range failed in part due to human conflict. I conducted focus group interviews in two communities bordering Alala historical range to assess participants' ability to recognize the Alala, and to understand how these community members value natural resources. I found that although very few participants recognized the Alala, many expressed curiosity and concern for the species. Participants demonstrated predominantly utilitarian views towards natural resources but these value orientations were steeped with cultural significance. Alala recovery efforts will benefit through emphasis of both the utilitarian and cultural value of this species. Reintroduction projects in Hawaii and elsewhere should dedicate a portion of their resources towards understanding the perspectives of the human communities surrounding future reintroduction sites. This approach will help avoid potential conflicts before they arise and maximize the likelihood of success by building programs based on shared values.
Open Access
Impacts of elk management and riparian condition on songbirds in Rocky Mountain National Park
(Colorado State University. Libraries, 2015) Craig, Apryle Dawn, author; Pejchar, Liba, advisor; Aldridge, Cameron, committee member; Noon, Barry, committee member; Bobowski, Ben, committee member
The widespread loss of apex predators from the western U.S. is having cascading effects on ecosystems. As in other western parks, riparian willow (Salix spp.) communities in Rocky Mountain National Park (RMNP) are declining as a result of a trophic cascade involving the local extinction of wolves (Canis lupus) and an exponential increase in elk (Cervus elaphus). In 2008, RMNP began installing elk exclosures to protect and restore willow communities and the diverse taxa that depend on riparian ecosystems from heavy browsing. Using point counts, I evaluated the effect of elk exclosures and riparian shrub condition on songbird density and occupancy. I found little support for a direct effect of elk exclosures on bird communities, with the exception of shrub nesting birds which occurred at higher densities within exclosures. However, the density and occupancy of some riparian bird species and guilds was positively correlated with particular vegetation conditions in this ecosystem. Shrub height positively related to both density and occupancy of Dusky Flycatcher. For the Lincoln Sparrow and shrub-nesting guild, occupancy also had a positive relationship with shrub height. The percent of shrub cover within 15 m of the survey point was an important positive predictor of density for Lincoln's Sparrows, Song Sparrows, and Wilson's Warblers, and foliage-gleaner and shrub-nesting guilds. The percent of riparian shrub cover within 300 m was an important positive predictor for the density of Wilson's Warblers. American Robin, a habitat generalist, and ground-nesting and foraging guilds did not respond strongly to shrub cover or height at any scale. These results reflect the variable shrub conditions inside and outside exclosures, and affirm that managing for mid to high density shrub cover and height will be beneficial for some riparian specialists. My findings provide park managers critical information on bird communities in experimental elk exclosures, and insight into the conditions needed to support songbird communities in the park's riparian ecosystems.
Open Access
Improving ungulate habitat in a region undergoing rapid energy development: consequences for songbirds and small mammals
(Colorado State University. Libraries, 2014) Bombaci, Sara Petrita, author; Pejchar, Liba, advisor; Wilson, Kenneth R., committee member; Paschke, Mark, committee member
Habitat manipulation intended to mitigate the impact of energy development on game animals is well underway in the western U.S. Yet, the consequences of these actions for other species are not well understood. A habitat manipulation experiment was established in the Piceance Basin, a region of Colorado undergoing rapid energy development, to evaluate alternative methods (i.e. chaining, hydro-axe, and roller-chop treatments) for reducing pinyon-juniper woodlands to promote mule deer habitat. I use this experimental design to additionally test the initial effects of these treatments on birds and small mammals, and to evaluate selection of habitat components in treatments by birds and small mammals. I found lower bird species occupancy in all treatment plots compared to control plots; however the strength of this response varied by bird guild. I found a positive relationship between bird species occupancy and percent tree cover and a negative relationship between bird species occupancy and percent grass and forb cover. I found no evidence of differences in small mammal species occupancy or density between controls and treatments. I found a positive relationship between small mammal species occupancy and percent grass and forb cover. Species richness did not significantly differ between control and treatment plots for birds or small mammals. My approach and research findings can be used to inform habitat management and multiple-species conservation objectives in pinyon-juniper and sage-steppe ecosystems undergoing energy development. Specifically, I have identified that recently developed roller-chop and hydro-axe treatments have similar impacts to woodland bird guilds as traditional chaining treatments. I have also identified species that are sensitive to habitat mitigation treatments, and thus should be monitored if woodland reduction continues to be used as a habitat mitigation strategy. Since all bird guilds were positively associated with tree cover, woodland reduction strategies that promote landscape heterogeneity by leaving standing trees to provide structure for birds may have fewer impacts than those that clear large contiguous patches of woodland. This approach has the potential to increase the conservation value of habitat mitigation treatments for pinyon-juniper obligates as well as shrubland and grassland species.
Open Access
Mammalian habitat use along a residential development gradient in northern Colorado
(Colorado State University. Libraries, 2013) Goad, Erica H., author; Pejchar, Liba, advisor; Knight, Richard L., advisor; Reed, Sarah E., committee member; Sibold, Jason S., committee member
"Exurban" development occupies nearly five times more land in the United States than urban and suburban development combined. Understanding the effects of exurban development on biodiversity thus has important and wide-ranging implications for the planning, construction and stewardship of sustainable communities and surrounding rural lands. To assess the impact of exurban development on mammalian habitat use, wildlife cameras were placed along a unique development gradient designed to capture landscape permeability in a rapidly growing rural region of Colorado. Multiple-season species occupancy and relative activity (frequency of detections) were measured in summer and winter seasons and these data were analyzed in conjunction with a novel, acoustic-based approach to assessing human activity. Impacts of exurban housing varied by mammal species, with some species, such as bobcats, elk, and coyotes, showing decreased activity and occupancy levels at higher housing densities, whereas others, including red foxes and Abert's squirrels, occurred more frequently in these areas. Human-sourced activities associated with development and non-natural sound levels emerged as top models for most species. Relative activity rates corroborated occupancy results, indicating that some species not only use habitat in high density areas, they use it more frequently. In addition, some species, including black bears, preferentially used embedded greenbelts in high-density exurban subdivisions, suggesting that greenbelts may be important for structural and functional connectivity. This study demonstrates that the impacts of exurban development are species-dependent. However, incorporating well-designed and naturally vegetated open spaces into development projects and minimizing human disturbance may be critical to mitigating development impacts to most wildlife in regions undergoing continued exurban expansion.
Open Access
Restoring island birds and seed dispersal in New Zealand's fenced mainland island sanctuaries
(Colorado State University. Libraries, 2018) Bombaci, Sara Petrita, author; Pejchar, Liba, advisor; Reed, Sarah, committee member; Savidge, Julie, committee member; Smith, Melinda, committee member
Island ecosystems are global biodiversity hotspots, but many island species face population declines and extinction. These losses are mainly driven by invasive mammals that consume or compete with native animals and degrade their habitats. The decline of island animal populations may also impact ecosystem processes that depend on them, e.g. seed dispersal, pollination, and nutrient cycling. The island nation of New Zealand has pioneered a unique solution – fenced mainland island sanctuaries – which exclude invasive mammals from natural habitats and provide opportunities to restore native birds and other wildlife. Yet, critics question whether sanctuaries, which are costly and require continuous maintenance, effectively conserve birds and ecosystems, given minimal research on sanctuary project outcomes. I assessed if sanctuaries are an effective conservation tool for restoring birds and seed dispersal in New Zealand. I compared bird population densities and bird-mediated seed dispersal in three fenced sanctuary sites to three paired reference sites (with minimal mammal control). From January-April 2016 and 2017, I set seed traps to measure dispersed-seed abundance, conducted focal tree observations to determine foraging rates for six tree species, and used distance sampling-based point counts to survey birds at randomly placed sampling locations within each site. I supplemented my bird surveys with a paired acoustic sampling method that uses acoustic recorders to increase survey sample size when estimating population densities with distance sampling. I tested the effectiveness of paired acoustic sampling for monitoring New Zealand forest bird populations by assessing whether density estimates from acoustic data were biased relative to densities estimated from human point counts, and by assessing whether the paired acoustic sampling method corrects bias from acoustic data, when present. Thus, the objectives of this dissertation were to assess 1) whether audio data could be used to estimate population densities for New Zealand forest birds (Chapter 1), 2) whether fenced mainland island sanctuaries increase the density of native or introduced bird species relative to unprotected areas in New Zealand (Chapter 2), and 3) whether sanctuaries enhance bird-mediated seed dispersal (foraging rates and dispersed-seed abundance) relative to unprotected areas (Chapter 3). I found that acoustic recorders underestimated bird population densities for four bird species but incorporating statistical offsets from the paired sampling method in generalized linear mixed models corrected the bias for all four species. Across both years, I found 0.27 to 9.00 more birds/ha on average for nine of twelve native bird species (including seven frugivores) in sanctuaries compared to unprotected sites, and no difference in mean population densities for three introduced bird species (two frugivores) and three biogeographically recent native species (one frugivore). Mean foraging rates and dispersed seed counts were also higher (0.1-0.6 more fruits consumed/observation period; 2-22 more seeds dispersed/plot) in sanctuary sites for several native tree species. Frugivore density, or both frugivore density and fruit abundance were significant positive predictors of foraging rates and dispersed seed counts for most tree species. Finally, native bird densities were correlated with foraging rates and dispersed seed counts for most tree species, but introduced bird densities were rarely correlated with foraging or dispersed seed counts. Thus, higher densities of native frugivorous birds in sanctuary sites appears to have resulted in increased fruit removal and dispersed seed counts for several native tree species. My study is one of the first to demonstrate that fenced mainland island sanctuaries, which require a substantial investment of conservation funds, are meeting ecological objectives. Furthermore, I demonstrate that paired acoustic sampling can be used to produce unbiased population density estimates from acoustic data, relative to human point counts, which holds great promise for increasing the scope and efficiency of bird population monitoring in New Zealand. I show that sanctuaries increase bird population densities for several native bird species and have no effect on introduced and biogeographically recent native species. These findings support predictions made over a decade ago on the potential 'winners' and 'losers' of mammal eradication and offer evidence that fenced sanctuaries effectively conserve New Zealand's native bird populations. By increasing bird densities and seed dispersal, fenced mainland island sanctuaries could be a viable tool for restoring other island and mainland ecosystems under threat from invasive mammals.
Open Access
Social and ecological aspects of conservation development as a strategy for biodiversity conservation on private lands
(Colorado State University. Libraries, 2015) Farr, Cooper Marie, author; Pejchar, Liba, advisor; Reed, Sarah E., advisor; Bailey, Larissa L., committee member; Seidl, Andrew F., committee member
Private lands harbor a large proportion of the world’s biodiversity, and they are also facing widespread threats from extractive land uses, anthropogenic disturbances, and land conversion for residential and commercial development. With decreased funding and support for public land acquisition and management, developing effective and economically viable tools for conservation on private lands is increasingly important. One method is conservation development (CD), an alternative to residential sprawl designed to decrease negative environmental impacts by clustering houses in a small portion of a property while preserving the remaining land as protected open space. Although CD makes up approximately one-fourth of all of the private lands conserved in the U.S., little research has assessed where and why this tool is implemented, long-term management of CD open space, or specific positive or negative effects on wildlife communities. I conducted a thorough investigation of CD as a private land conservation strategy using a variety of methods. In chapter one, I investigated CD’s ability to successfully protect animal populations by examining bird and mammal occurrence in 14 CD subdivisions (range: 14-432 ha) in Northern Colorado, USA. Using point count and camera trap data in an occupancy modeling framework, I evaluated the relative importance of 9 subdivision design factors (e.g. housing density, proportion of CD preserved, total area of the protected space) and 14 stewardship factors (e.g. mowing, livestock, native vegetation cover) in influencing the richness of human-sensitive and human-adapted species and probability of use by 16 birds and 6 mammals. I found that bird and mammal species richness and habitat use were associated predominantly with design characteristics that maximize the natural or undisturbed land area both within and surrounding the development (e.g., proportion of CD preserved, total area of the protected space, proportion of natural land cover types at large scales). Habitat use by birds was frequently influenced by local habitat composition and quality, and several bird and mammal species had decreased habitat use in areas with increased localized disturbances such as the presence of humans and mowing in the open space. In chapter two, I used Social Network Analysis (SNA) to examine participation of individuals and companies (actors) in CD implementation. Using data gathered from public county records, I quantified actor participation in CD subdivisions in six counties in Colorado, USA. I examined and compared the patterns of actor participation in CDs among counties and identified the individuals and organizations that were most consistently associated with the implementation of CDs within each county. I found that social networks of actor participation in CD differed among counties, and network characteristics varied depending on the population of the county, the total number of CDs in the county, and the total number of actors in the network. My results also showed that the most highly connected actors that were consistently involved in the implementation of many CDs were biological and geological consultants, surveyors, engineers, and planners. In chapter three, I formally assessed the content of management plans and conservation easements for existing CD subdivisions in six Colorado counties. I quantified the proportion of CDs with management documents. I also examined the land uses and stewardship activities that were prohibited, permitted, encouraged or required in the protected open space of existing CDs. I determined which activities and practices were most and least frequently addressed in these documents in order to prioritize strategies to improve CD as an effective private land conservation tool. More than two-thirds (69%) of 302 CDs had documents on file that included guidelines and regulations for the long-term stewardship of the protected land. However, CD management documents rarely mentioned issues relating to wildlife habitat improvement, species-specific monitoring and management, homeowner education, and access to the open space by domestic pets. This research identifies several key design and stewardship factors that influence the conservation value of CD open space for birds and mammals, and the key actors and actor types in CD implementation. These findings can inform the strategies used to communicate recommendations to improve CD effectiveness at achieving conservation objectives. This research also examines the current strengths and weaknesses in the documents that guide stewardship of CD subdivisions. Using these findings, I made recommendations for critical guidelines and regulation that should be included in management documents to attain conservation benefits. By incorporating characteristics that promote the persistence of sensitive animal species on private lands, CDs have strong potential to balance the housing needs of growing human populations with the preservation of diverse and abundant animal communities. With direct application to improving the way that CDs are designed, developed and managed, my findings could enhance the potential of CD to sustain native biodiversity on private lands.
Open Access
The effectiveness of urban conservation programs for engaging the public and enhancing wildlife habitat
(Colorado State University. Libraries, 2019) Jimenez, Miguel F., author; Pejchar, Liba, advisor; Reed, Sarah, advisor; McHale, Melissa, committee member
The ecological and social effects of urbanization pose significant threats to global biodiversity. Habitat loss and fragmentation associated with urban development often displace native, human-sensitive species and replace them with exotic and human-adapted species. Urban residents also have limited access to natural areas, which may limit public support for conservation. Given these challenges, effectively engaging the public in conservation initiatives is increasingly important. The Nature in the City (NIC) initiative was launched in 2014 by the City of Fort Collins to create: "a connected open space network accessible to the entire community that provides a variety of experiences and functional habitat for people, plants, and wildlife." Here, I evaluated the extent to which two NIC programs achieved their goals to monitor plant and animal communities, enhance habitat for native species, and engage the public in conservation. My first chapter focused on the NIC Biodiversity Project, a citizen science ecological monitoring program. This program recruits and trains volunteers to collect data on the distribution of birds and butterflies across Fort Collins. Specifically, I assessed the tradeoffs associated with collecting data with citizen scientists as compared to paid technicians in terms of 1) data quality, 2) cost efficiency, and 3) the effectiveness of public engagement. I found mixed results for data quality; the probability of detecting human-adapted species was similar for citizen scientists and technicians, but citizen scientists were less likely to detect human-sensitive species. Additionally, citizen scientists tended to over report the abundance of human-adapted birds as compared to technicians. Habitat use estimates for four out of five species were comparable between data collected by citizen scientists and technicians. Citizen scientists were more cost efficient, producing more surveys and detections per paid work-hour than paid technicians. Finally, the citizen science program increased volunteers' ability to identify local wildlife and intentions to participate in similar programs but did not affect nature relatedness and self-efficacy for environmental action. My second chapter focused on the City of Fort Collin's Certified Natural Areas (CNA) program, which encourages private landowners to engage in stewardship practices that provide habitat for native plants and animals. I assessed 1) whether the CNA program increased native vegetation cover and vegetation structural heterogeneity, 2) provided habitat for human-sensitive birds and butterflies, and 3) which site- or landscape-level factors influenced these outcomes. I compared 10 residential open spaces not enrolled in the CNA program, 10 enhanced residential open spaces enrolled in the CNA program and 12 public natural areas managed by the City of Fort Collins. Although I did not detect significant differences in the amount of native vegetation cover or structure across site types, enhanced residential open spaces and public natural areas had consistently less mowed vegetation cover than residential open spaces, which was associated with more detections of insectivorous and shrub-nesting bird species. I also detected more human-sensitive bird species in enhanced residential open spaces than residential open space and found that across all sites, native vegetation was positively related to butterfly richness. Together, these results demonstrate that although enhanced residential open spaces are not a substitute for public natural areas providing high-quality habitat for human-sensitive wildlife, even relatively simple stewardship practices, such as not mowing vegetation, can have a positive influence on bird and butterfly communities in urban neighborhoods.
Open Access
The impact of energy sprawl on biodiversity and ecosystem services
(Colorado State University. Libraries, 2012) Jones, Nathan Forrest, author; Pejchar, Liba, advisor; Theobald, David M., committee member; Aldridge, Cameron L., committee member
The future of energy production is uncertain as society demands clean and abundant energy to meet the needs of a growing and increasingly developed population. Wind energy offers the benefit of reduced greenhouse gas emissions; however, like conventional power sources such as oil and natural gas, wind energy results in an environmental footprint that contributes to energy sprawl, or the use and degradation of land due to energy production. In order to better understand these potential affects I summarized and evaluated the impacts on a diverse set of indicators including habitat loss, fragmentation, wildlife mortality, noise and light pollution, invasive species, and changes in carbon stock and water resources. I quantified these indicators by digitizing the land-use footprint within 375 randomly selected one kilometer diameter plots, stratified across each energy type, within Colorado and Wyoming, USA. I found substantial differences in impacts between energy types for most indicators, although the magnitude and direction of the differences varied. Wind energy resulted in greater impacts to noise and light pollution whereas oil and natural gas development resulted in greater habitat fragmentation and impacts to biomass carbon stock and water resources. Underlying land-use and location of production activities were a critical factor in describing the impacts. This novel technique and my specific findings can be used by developers, planners and policy-makers to design energy development that retains biodiversity while meeting society's demand for energy.

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