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Zhang T, Xu Y, Ran J. Quantitative evaluation of the global impacts of human land modification on raptors. CONSERVATION BIOLOGY : THE JOURNAL OF THE SOCIETY FOR CONSERVATION BIOLOGY 2024; 38:e14228. [PMID: 38441344 DOI: 10.1111/cobi.14228] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 09/25/2023] [Accepted: 11/29/2023] [Indexed: 05/30/2024]
Abstract
Raptors are threatened by anthropogenic land modifications, but targeted quantitative assessment of these impacts is lacking. We conducted the first global quantitative evaluation of the impacts of human-modified land on raptors. We used eBird data from 2001 to 2020 on 425 raptor species and occupancy models to assess the impacts of human-modified land on raptor distribution. The mean spatiotemporal correlations of human settlement, cropland, and pasture with raptor occupancy probability were -0.048 (SE 0.031), -0.134 (0.032), and -0.145 (0.032), respectively. The mean sensitivity of raptor occupancy probability to settlement, cropland, and pasture was -5.760 (2.266), -3.128 (1.540), and -2.402 (1.551), respectively. The occupancy probability of raptors with a large body mass was more negatively correlated with cropland (phylogenetic generalized least squares regressions: slope = -0.052 [SE 0.022], t = -2.335, df = 1, 407, p = 0.020, λ = 0.006) and more positively correlated with pasture (slope = 0.047 [0.022], t = 2.118, df = 1, 407, p = 0.035, λ = 0.013). The occupancy probability of raptors with a more extensive range size was more positively correlated with cropland (slope = 0.002 [0.004], t = 0.399, df = 1, 407, p < 0.001, λ = 0.000). Raptors that prefer open habitats were more positively correlated with cropland (analysis of variance: F = 3.424, df = 2, p = 0.034, λ = 0.000) and pasture (F = 6.577, df = 2, p = 0.002, λ = 0.000). In Africa and South America, where raptor species are most abundant, raptor occupancy probability decreased over 20 years, most likely due to habitat fragmentation associated with human land modification. Although raptors with different ecological characteristics had different responses to human land modification, the impacts of settlement, cropland, and pasture on mean raptor occupancy probability were negative, regardless of space and time.
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Affiliation(s)
- Taxing Zhang
- Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, China
- Sichuan Key Laboratory of Conservation Biology on Endangered Wildlife, Sichuan University, Chengdu, China
| | - Yu Xu
- School of Life Sciences, Guizhou Normal University, Guiyang, China
| | - Jianghong Ran
- Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, China
- Sichuan Key Laboratory of Conservation Biology on Endangered Wildlife, Sichuan University, Chengdu, China
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Yackulic CB, Bailey LL, Dugger KM, Davis RJ, Franklin AB, Forsman ED, Ackers SH, Andrews LS, Diller LV, Gremel SA, Hamm KA, Herter DR, Higley JM, Horn RB, McCafferty C, Reid JA, Rockweit JT, Sovern SG. The past and future roles of competition and habitat in the range-wide occupancy dynamics of Northern Spotted Owls. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2019; 29:e01861. [PMID: 30835921 DOI: 10.1002/eap.1861] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Revised: 12/17/2018] [Accepted: 01/07/2019] [Indexed: 06/09/2023]
Abstract
Slow ecological processes challenge conservation. Short-term variability can obscure the importance of slower processes that may ultimately determine the state of a system. Furthermore, management actions with slow responses can be hard to justify. One response to slow processes is to explicitly concentrate analysis on state dynamics. Here, we focus on identifying drivers of Northern Spotted Owl (Strix occidentalis caurina) territorial occupancy dynamics across 11 study areas spanning their geographic range and forecasting response to potential management actions. Competition with Barred Owls (Strix varia) has increased Spotted Owl territory extinction probabilities across all study areas and driven recent declines in Spotted Owl populations. Without management intervention, the Northern Spotted Owl subspecies will be extirpated from parts of its current range within decades. In the short term, Barred Owl removal can be effective. Over longer time spans, however, maintaining or improving habitat conditions can help promote the persistence of northern spotted owl populations. In most study areas, habitat effects on expected Northern Spotted Owl territorial occupancy are actually greater than the effects of competition from Barred Owls. This study suggests how intensive management actions (removal of a competitor) with rapid results can complement a slower management action (i.e., promoting forest succession).
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Affiliation(s)
- Charles B Yackulic
- U.S. Geological Survey, Southwest Biological Science Center, Flagstaff, Arizona, 86001, USA
| | - Larissa L Bailey
- Department of Fish, Wildlife, and Conservation Biology, Graduate Degree Program in Ecology, Colorado State University, Fort Collins, Colorado, 80523, USA
| | - Katie M Dugger
- U.S. Geological Survey, Oregon Cooperative Fish and Wildlife Research Unit, Department of Fisheries and Wildlife, Oregon State University, Corvallis, Oregon, 97331, USA
| | - Raymond J Davis
- USDA Forest Service, Pacific Northwest Research Station, Forestry Sciences Laboratory, Corvallis, Oregon, 97331, USA
| | - Alan B Franklin
- USDA APHIS National Wildlife Research Center, Fort Collins, Colorado, 80521, USA
| | - Eric D Forsman
- USDA Forest Service, Pacific Northwest Research Station, Forestry Sciences Laboratory, Corvallis, Oregon, 97331, USA
| | - Steven H Ackers
- Oregon Cooperative Fish and Wildlife Research Unit, Department of Fisheries and Wildlife, Oregon State University, Corvallis, Oregon, 97331, USA
| | - Lawrence S Andrews
- Oregon Cooperative Fish and Wildlife Research Unit, Department of Fisheries and Wildlife, Oregon State University, Corvallis, Oregon, 97331, USA
| | - Lowell V Diller
- Green Diamond Resource Company, Korbel, California, 95550, USA
| | - Scott A Gremel
- USDI National Park Service, Olympic National Park, Port Angeles, Washington, 98362, USA
| | - Keith A Hamm
- Green Diamond Resource Company, Korbel, California, 95550, USA
| | | | - J Mark Higley
- Hoopa Tribal Forestry, Hoopa, California, 95546, USA
| | - Rob B Horn
- USDI Bureau of Land Management, Roseburg District Office, Roseburg, Oregon, 97471, USA
| | - Christopher McCafferty
- Oregon Cooperative Fish and Wildlife Research Unit, Department of Fisheries and Wildlife, Oregon State University, Corvallis, Oregon, 97331, USA
| | - Janice A Reid
- USDA Forest Service, Pacific Northwest Research Station, Roseburg Field Station, Roseburg, Oregon, 97471, USA
| | - Jeremy T Rockweit
- Department of Fish, Wildlife, and Conservation Biology, Graduate Degree Program in Ecology, Colorado State University, Fort Collins, Colorado, 80523, USA
| | - Stan G Sovern
- Oregon Cooperative Fish and Wildlife Research Unit, Department of Fisheries and Wildlife, Oregon State University, Corvallis, Oregon, 97331, USA
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Srivathsa A, Karanth KU, Kumar NS, Oli MK. Insights from distribution dynamics inform strategies to conserve a dhole Cuon alpinus metapopulation in India. Sci Rep 2019; 9:3081. [PMID: 30816170 PMCID: PMC6395595 DOI: 10.1038/s41598-019-39293-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Accepted: 01/18/2019] [Indexed: 11/09/2022] Open
Abstract
Most large carnivore populations currently occur in heterogeneous landscapes, with source populations embedded in a matrix of human-dominated habitats. Understanding changes in distribution of endangered carnivores is critical for prioritizing and implementing conservation strategies. We examined distribution and dynamics of a dhole Cuon alpinus metapopulation, first in 2007 and subsequently in 2015, based on indirect sign surveys across 37, 000sq. km of India's Western Ghats. Predicted dhole occupancy declined from 0.62 (95% CI: 0.58-0.66) in 2007 to 0.54 (95% CI: 0.50-0.58) in 2015. Occupancy was associated with abundance of primary prey species and anthropogenic disturbance. Local extinction appeared to be influenced by forest cover loss, and offset by protected reserves; colonization was influenced by occupancy in neighbouring sites. Perturbation analysis indicated that occupancy was more sensitive to local extinction within reserves and to colonization in sites abutting reserves. The Western Ghats could serve as a stronghold for the endangered dhole, provided future colonizations are facilitated through habitat consolidation beyond reserve boundaries, and local extinctions are prevented by increasing protection efforts within select reserves. We advocate for wildlife managers to adopt a landscape-based approach and periodic monitoring to ensure persistence of the dhole metapopulation in Western Ghats, and in other critical conservation regions across the species' geographic range.
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Affiliation(s)
- Arjun Srivathsa
- School of Natural Resources and Environment, University of Florida, Gainesville, FL, USA.
- Department of Wildlife Ecology and Conservation, University of Florida, Gainesville, FL, USA.
- Wildlife Conservation Society-India, Bengaluru, India.
- Centre for Wildlife Studies, Bengaluru, India.
| | - K Ullas Karanth
- Centre for Wildlife Studies, Bengaluru, India
- Wildlife Conservation Society, Global Conservation Program, New York, NY, USA
- National Centre for Biological Sciences, Bengaluru, India
| | - N Samba Kumar
- Wildlife Conservation Society-India, Bengaluru, India
- Centre for Wildlife Studies, Bengaluru, India
| | - Madan K Oli
- School of Natural Resources and Environment, University of Florida, Gainesville, FL, USA
- Department of Wildlife Ecology and Conservation, University of Florida, Gainesville, FL, USA
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Miller DAW, Grant EHC, Muths E, Amburgey SM, Adams MJ, Joseph MB, Waddle JH, Johnson PTJ, Ryan ME, Schmidt BR, Calhoun DL, Davis CL, Fisher RN, Green DM, Hossack BR, Rittenhouse TAG, Walls SC, Bailey LL, Cruickshank SS, Fellers GM, Gorman TA, Haas CA, Hughson W, Pilliod DS, Price SJ, Ray AM, Sadinski W, Saenz D, Barichivich WJ, Brand A, Brehme CS, Dagit R, Delaney KS, Glorioso BM, Kats LB, Kleeman PM, Pearl CA, Rochester CJ, Riley SPD, Roth M, Sigafus BH. Quantifying climate sensitivity and climate-driven change in North American amphibian communities. Nat Commun 2018; 9:3926. [PMID: 30254220 PMCID: PMC6156563 DOI: 10.1038/s41467-018-06157-6] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2017] [Accepted: 08/16/2018] [Indexed: 11/09/2022] Open
Abstract
Changing climate will impact species' ranges only when environmental variability directly impacts the demography of local populations. However, measurement of demographic responses to climate change has largely been limited to single species and locations. Here we show that amphibian communities are responsive to climatic variability, using >500,000 time-series observations for 81 species across 86 North American study areas. The effect of climate on local colonization and persistence probabilities varies among eco-regions and depends on local climate, species life-histories, and taxonomic classification. We found that local species richness is most sensitive to changes in water availability during breeding and changes in winter conditions. Based on the relationships we measure, recent changes in climate cannot explain why local species richness of North American amphibians has rapidly declined. However, changing climate does explain why some populations are declining faster than others. Our results provide important insights into how amphibians respond to climate and a general framework for measuring climate impacts on species richness.
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Affiliation(s)
- David A W Miller
- Department of Ecosystem Science and Management, Pennsylvania State University, University Park, PA, 16802, USA.
| | - Evan H Campbell Grant
- U.S. Geological Survey, Patuxent Wildlife Research Center, SO Conte Anadromous Fish Lab, 1 Migratory Way, Turners Falls, MA, 01376, USA.
| | - Erin Muths
- U.S. Geological Survey, Fort Collins Science Center, Fort Collins, CO, 80523, USA.
| | - Staci M Amburgey
- Department of Ecosystem Science and Management, Pennsylvania State University, University Park, PA, 16802, USA
- Intercollege Graduate Ecology Program, Pennsylvania State University, University Park, PA, 16802, USA
| | - Michael J Adams
- U.S. Geological Survey, Forest and Rangeland Ecosystem Science Center, Corvallis, OR, 97331, USA
| | - Maxwell B Joseph
- Ecology and Evolutionary Biology Department, University of Colorado, Boulder, Boulder, CO, 80309, USA
| | - J Hardin Waddle
- U.S. Geological Survey, Wetland and Aquatic Research Center, Lafayette, LA, 70506, USA
| | - Pieter T J Johnson
- Ecology and Evolutionary Biology Department, University of Colorado, Boulder, Boulder, CO, 80309, USA
| | - Maureen E Ryan
- School of Environment and Forest Sciences, University of Washington, Seattle, WA, 98195, USA
- Conservation Science Partners, Seattle, WA, 98102, USA
| | - Benedikt R Schmidt
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, 8057, Switzerland
- Info Fauna Karch, 2000, Neuchâtel, Switzerland
| | - Daniel L Calhoun
- U.S. Geological Survey, South Atlantic Water Science Center, Norcross, GA, 30093, USA
| | - Courtney L Davis
- Department of Ecosystem Science and Management, Pennsylvania State University, University Park, PA, 16802, USA
- Intercollege Graduate Ecology Program, Pennsylvania State University, University Park, PA, 16802, USA
| | - Robert N Fisher
- U.S. Geological Survey, Western Ecological Research Center, San Diego, CA, 92101, USA
| | - David M Green
- Redpath Museum, McGill University, Montreal, QC, H3A 0C4, Canada
| | - Blake R Hossack
- U.S. Geological Survey, Northern Rocky Mountain Science Center, Aldo Leopold Wilderness Research Institute, Missoula, MT, 59801, USA
| | - Tracy A G Rittenhouse
- Department of Natural Resources and the Environment, University of Connecticut, Storrs, CT, 06269, USA
| | - Susan C Walls
- U.S. Geological Survey, Wetland and Aquatic Research Center, Gainesville, FL, 32653, USA
| | - Larissa L Bailey
- Department of Fish, Wildlife and Conservation Biology, Colorado State University, Fort Collins, CO, 80523, USA
| | - Sam S Cruickshank
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, 8057, Switzerland
| | - Gary M Fellers
- U.S. Geological Survey, Western Ecological Research Center, Point Reyes Station, CA, 94956, USA
| | - Thomas A Gorman
- Department of Fish and Wildlife Conservation, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Carola A Haas
- Department of Fish and Wildlife Conservation, Virginia Tech, Blacksburg, VA, 24061, USA
| | | | - David S Pilliod
- U.S. Geological Survey, Forest and Rangeland Ecosystem Science Center, Boise, ID, 83706, USA
| | - Steven J Price
- Department of Forestry and Natural Resources, University of Kentucky, Lexington, KY, 40506, USA
| | - Andrew M Ray
- Greater Yellowstone Network, National Park Service, Bozeman, MT, 59715, USA
| | - Walt Sadinski
- U.S. Geological Survey, Upper Midwest Environmental Sciences Center, La Crosse, WI, 54603, USA
| | - Daniel Saenz
- U. S. Department of Agriculture, Southern Research Station, Forest Service, Nacogdoches, TX, 75965, USA
| | - William J Barichivich
- U.S. Geological Survey, Wetland and Aquatic Research Center, Gainesville, FL, 32653, USA
| | - Adrianne Brand
- U.S. Geological Survey, Patuxent Wildlife Research Center, SO Conte Anadromous Fish Lab, 1 Migratory Way, Turners Falls, MA, 01376, USA
| | - Cheryl S Brehme
- U.S. Geological Survey, Western Ecological Research Center, San Diego, CA, 92101, USA
| | - Rosi Dagit
- Resource Conservation District of the Santa Monica Mountains, Topanga, CA, 90290, USA
| | - Katy S Delaney
- National Park Service-Santa Monica Mountains Recreation Area, Thousand Oaks, CA, 91360, USA
| | - Brad M Glorioso
- U.S. Geological Survey, Wetland and Aquatic Research Center, Lafayette, LA, 70506, USA
| | - Lee B Kats
- Natural Sciences Division, Seaver College, Pepperdine University, Malibu, CA, 90263, USA
| | - Patrick M Kleeman
- U.S. Geological Survey, Western Ecological Research Center, Point Reyes Station, CA, 94956, USA
| | - Christopher A Pearl
- U.S. Geological Survey, Forest and Rangeland Ecosystem Science Center, Corvallis, OR, 97331, USA
| | - Carlton J Rochester
- U.S. Geological Survey, Western Ecological Research Center, San Diego, CA, 92101, USA
| | - Seth P D Riley
- National Park Service-Santa Monica Mountains Recreation Area, Thousand Oaks, CA, 91360, USA
| | - Mark Roth
- U.S. Geological Survey, Upper Midwest Environmental Sciences Center, La Crosse, WI, 54603, USA
| | - Brent H Sigafus
- U.S. Geological Survey, Southwest Biological Science Center, Tucson, AZ, 85719, USA
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Davis CL, Miller DAW, Walls SC, Barichivich WJ, Riley JW, Brown ME. Species interactions and the effects of climate variability on a wetland amphibian metacommunity. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2017; 27:285-296. [PMID: 28052496 DOI: 10.1002/eap.1442] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Revised: 08/01/2016] [Accepted: 09/07/2016] [Indexed: 06/06/2023]
Abstract
Disentangling the role that multiple interacting factors have on species responses to shifting climate poses a significant challenge. However, our ability to do so is of utmost importance to predict the effects of climate change on species distributions. We examined how populations of three species of wetland-breeding amphibians, which varied in life history requirements, responded to a six-year period of extremely variable precipitation. This interval was punctuated by both extensive drought and heavy precipitation and flooding, providing a natural experiment to measure community responses to environmental perturbations. We estimated occurrence dynamics using a discrete hidden Markov modeling approach that incorporated information regarding habitat state and predator-prey interactions. This approach allowed us to measure how metapopulation dynamics of each amphibian species was affected by interactions among weather, wetland hydroperiod, and co-occurrence with fish predators. The pig frog, a generalist, proved most resistant to perturbations, with both colonization and persistence being unaffected by seasonal variation in precipitation or co-occurrence with fishes. The ornate chorus frog, an ephemeral wetland specialist, responded positively to periods of drought owing to increased persistence and colonization rates during periods of low-rainfall. Low probabilities of occurrence of the ornate chorus frog in long-duration wetlands were driven by interactions with predators due to low colonization rates when fishes were present. The mole salamander was most sensitive to shifts in water availability. In our study area, this species never occurred in short-duration wetlands and persistence probabilities decreased during periods of drought. At the same time, negative effects occurred with extreme precipitation because flooding facilitated colonization of fishes to isolated wetlands and mole salamanders did not colonize wetlands once fishes were present. We demonstrate that the effects of changes in water availability depend on interactions with predators and wetland type and are influenced by the life history of each of our species. The dynamic species occurrence modeling approach we used offers promise for other systems when the goal is to disentangle the complex interactions that determine species responses to environmental variability.
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Affiliation(s)
- Courtney L Davis
- Department of Ecosystem Science and Management, Pennsylvania State University, University Park, Pennsylvania, 16802, USA
- Intercollege Graduate Ecology Program, Pennsylvania State University, University Park, Pennsylvania, 16802, USA
| | - David A W Miller
- Department of Ecosystem Science and Management, Pennsylvania State University, University Park, Pennsylvania, 16802, USA
| | - Susan C Walls
- Wetland and Aquatic Research Center, United States Geological Survey, Gainesville, Florida, 32653, USA
| | - William J Barichivich
- Wetland and Aquatic Research Center, United States Geological Survey, Gainesville, Florida, 32653, USA
| | - Jeffrey W Riley
- South Atlantic Water Science Center, United States Geological Survey, Norcross, Georgia, 30093, USA
| | - Mary E Brown
- Cherokee Nation Technology Solutions Contracted to the Wetland and Aquatic Research Center, United States Geological Survey, Gainesville, Florida, 32653, USA
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Miller DAW, Brehme CS, Hines JE, Nichols JD, Fisher RN. Joint estimation of habitat dynamics and species interactions: disturbance reduces co-occurrence of non-native predators with an endangered toad. J Anim Ecol 2012; 81:1288-1297. [PMID: 22702337 DOI: 10.1111/j.1365-2656.2012.02001.x] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
1. Ecologists have long been interested in the processes that determine patterns of species occurrence and co-occurrence. Potential short-comings of many existing empirical approaches that address these questions include a reliance on patterns of occurrence at a single time point, failure to account properly for imperfect detection and treating the environment as a static variable. 2. We fit detection and non-detection data collected from repeat visits using a dynamic site occupancy model that simultaneously accounts for the temporal dynamics of a focal prey species, its predators and its habitat. Our objective was to determine how disturbance and species interactions affect the co-occurrence probabilities of an endangered toad and recently introduced non-native predators in stream breeding habitats. For this, we determined statistical support for alternative processes that could affect co-occurrence frequency in the system. 3. We collected occurrence data at stream segments in two watersheds where streams were largely ephemeral and one watershed dominated by perennial streams. Co-occurrence probabilities of toads with non-native predators were related to disturbance frequency, with low co-occurrence in the ephemeral watershed and high co-occurrence in the perennial watershed. This occurred because once predators were established at a site, they were rarely lost from the site except in cases when the site dried out. Once dry sites became suitable again, toads colonized them much more rapidly than predators, creating a period of predator-free space. 4. We attribute the dynamics to a storage effect, where toads persisting outside the stream environment during periods of drought rapidly colonized sites when they become suitable again. Our results support that even in highly connected stream networks, temporal disturbance can structure frequencies with which breeding amphibians encounter non-native predators. 5. Dynamic multi-state occupancy models are a powerful tool for rigorously examining hypotheses about inter-species and species-habitat interactions. In contrast to previous methods that infer dynamic processes based on static patterns in occupancy, the approach we took allows the dynamic processes that determine species-species and species-habitat interactions to be directly estimated.
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Affiliation(s)
- David A W Miller
- US Geological Survey, Patuxent Wildlife Research Center, 12100 Beech Forest Rd, Laurel, MD 20708, USAUS Geological Survey, Western Ecological Research Center, San Diego Field Station, 4165 Spruance Road, Suite 200, San Diego, CA 92101, USA
| | - Cheryl S Brehme
- US Geological Survey, Patuxent Wildlife Research Center, 12100 Beech Forest Rd, Laurel, MD 20708, USAUS Geological Survey, Western Ecological Research Center, San Diego Field Station, 4165 Spruance Road, Suite 200, San Diego, CA 92101, USA
| | - James E Hines
- US Geological Survey, Patuxent Wildlife Research Center, 12100 Beech Forest Rd, Laurel, MD 20708, USAUS Geological Survey, Western Ecological Research Center, San Diego Field Station, 4165 Spruance Road, Suite 200, San Diego, CA 92101, USA
| | - James D Nichols
- US Geological Survey, Patuxent Wildlife Research Center, 12100 Beech Forest Rd, Laurel, MD 20708, USAUS Geological Survey, Western Ecological Research Center, San Diego Field Station, 4165 Spruance Road, Suite 200, San Diego, CA 92101, USA
| | - Robert N Fisher
- US Geological Survey, Patuxent Wildlife Research Center, 12100 Beech Forest Rd, Laurel, MD 20708, USAUS Geological Survey, Western Ecological Research Center, San Diego Field Station, 4165 Spruance Road, Suite 200, San Diego, CA 92101, USA
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