Browsing by Subject "occupancy models"

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    Full Simulation Data and Worked Examples from Specht et al. Conditional Occupancy Manuscript
    (2017-02-27) Specht, Hannah S; Iannarilli, Fabiola; Edwards, Margaret R; Johnson, Michael K; Stapleton, Seth P; Weegman, Mitch; Yohannes, Brittney J; Arnold, Todd W; Reich, Henry T; spech030@umn.edu; Specht, Hannah M
    Occupancy models are widely used to describe the distribution of rare and cryptic species— those that occur on only a portion of the landscape and cannot be detected reliably during a single survey. However, occupancy models often provide inaccurate estimates of occupancy (ψ ̂) and detection probabilities (p ̂) under these circumstances. We developed a new "conditional" occupancy design that more accurately estimates occupancy for rare species. Here we provide the full simulation dataset used to compare estimation properties of standard, removal and conditional designs. Data were simulated in R and analyzed using MCMC methods in package R2jags. See Specht et al. (in review) for description of methods. Please cite Specht et al. in further use of this data set.
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    Habitat use and reproductive success of waterbirds in the human-dominated landscape of North America’s prairies: Using sparse data to inform management
    (2018-05) Specht, Hannah
    Information needed to implement effective management strategies requires an understanding of where, when and how target species use habitats available to them to survive and reproduce. I used new approaches for field data collection and analysis for rare and cryptic species to improve understanding of how anthropogenic and natural habitat characteristics affect the habitat use and reproductive success of grassland waterbirds, to better inform management in North America’s Northern Great Plains. Using historical data on waterfowl age ratios at banding and a database of upland shorebird nest records, I identified spatial and temporal variation in upland nesting waterfowl and shorebird fecundity. Specifically, I found positive relationships between vole population irruptions and metrics of fecundity (age ratios and nest survival) in both upland nesting waterfowl and shorebirds, and that fecundity of both groups was tightly tied to wetland conditions; increases in wetland inundation improved dabbling duck fecundity and Marbled Godwits (Limosa fedoa) experienced higher fecundity in territories with greater wetland cover. Density dependent effects were mixed across species. I used occupancy surveys with behavioral indicators of brood presence to assess whether habitat use by conservation concern upland shorebirds and Northern Pintail (Anas acuta) was altered by oil development in the Bakken oil field, using habitat suitability models to account for natural variation in habitat quality. I found reduced habitat use by breeding pairs and/or broods of all five studied species at sites with higher traffic and that Wilson’s phalarope (Phalaropus tricolor) breeding pairs avoided habitat with higher well density. Using behavior to infer brood presence facilitated identifying effects of traffic on brood habitat use where data would otherwise have been too sparse. Finally, I present a new occupancy survey sampling design that improves estimates for rare species. Management for upland-nesting waterbirds should continue to prioritize maintaining the capacity of less permanent wetland basins to rehydrate and active patch management of grassland. Infrastructure and activity that impacts grassland wildlife should be concentrated within corridors on the landscape while conservation should be concentrated in spaces between development corridors.