After a well-documented recovery following substantial population declines throughout most of North America, the Peregrine Falcon (Falco peregrinus) was delisted under provisions of the Endangered Species Act in 1999. Post-delisting monitoring for the Peregrine Falcon stipulated surveys of breeding locations and did not specifically emphasize other metrics of population dynamics such as survival. We used banding data from Peregrine Falcons captured on the Washington coast during 1212 vehicle surveys between 1995 and 2018 to assess apparent survival and resighting frequencies. Our mark-recapture data set included 226 Peregrine Falcons: 148 females and 78 males. Fourteen Peregrine Falcons were recovered dead and another eight were found injured or uninjured and unable to fly due to illness or substantially soiled feathers. We had 744 resightings, 67.1% (n = 499) by our research group during surveys (Group A) and 32.9% (n = 245) by others (Group B). We found a dramatic increase in Group B contributions beginning in 2008 due to the emergence of digital camera use in wildlife photography and increased public awareness of our project. Data from 1995 to 2018 supported the estimation of apparent survival for three age classes of Peregrine Falcons: 0.424 (SE = 0.057) for hatch-year (<1 yr old); 0.663 (SE = 0.066) for second-year (1–2 yr old), and 0.738 (SE = 0.030) for after-second-year (>2 yr old). Our long-term mark-resighting analyses of overwintering and migratory Peregrine Falcons along the Washington coast provide evidence of a reasonably high level of apparent survival that suggests good population performance.
Northern bobwhites have experienced population declines in Colorado and range wide. Estimating vital rates can provide clues to factors limiting population growth rate. Although recent estimates of breeding season survival in the northwest corner of the northern bobwhite range are available, there have been no recent studies on nonbreeding season survival. We used radio‐telemetry to estimate nonbreeding season (October–March) survival of northern bobwhites at two study sites in northeastern Colorado during winter 2019–2020 and 2020–2021. Based on our sample of 157 bobwhites, we found that survival was highly variable between years and was negatively affected by colder daily minimum temperatures and deeper snow depths. Seasonal (six‐month) survival during the first year was 0.219 (SE = 0.040) and during the second year was 0.006 (SE = 0.005). We found no evidence that sex, age or study site influenced survival, and very weak support for an effect of body mass. During our study, there were two extreme winter weather events, during which we found unusually high numbers of non‐predation mortality. Overall, northern bobwhite nonbreeding season survival in the northwest corner of their range appears to be generally similar to other regions, except during extreme winter weather events, which resulted in high mortality. We encourage managers to create or maintain vegetation characteristics that will provide shelter from winter weather while also providing abundant food in close proximity.
Raynor, E. J., C. E. Whalen, M. Bomberger Brown, and L. A. Powell. 2017. Location matters: evaluating Greater Prairie-Chicken (Tympanuchus cupido) boom chorus propagation. Avian Conservation and Ecology 12(2):17. https://doi.org/10.5751/ACE-01126-120217
Biologists often estimate separate survival and movement rites from radiotelemetry and markrecapture data from the same study population.We describe a method for combining these data types in a single model to obtain joint, potentially less biased estimates of survival and movement that use all available data.We furnish an example using wood thrushes (Hylocichla mustelina) captured at the Piedmont National Wildlife Refuge in central Georgia in 1996.The model structure allows estimation of survival and capture probabilities, as well as estimation of movements away from and into the study area.In addition, the model structure provides many possibilities for hypothesis testing.Using the combined model structure, we estimated that weekly survival of wood thrushes was 0.989 ?0.007 (-SE).Survival rates of banded and radiomarked individuals were not different (&[Sradioed, Sbanded] = log[Sradioed/Sbanded] = 0.0239, 95% CI = -0.0196 to 0.0486).Fidelity rates (weekly probability of remaining ih a stratum) did not differ between geographic strata (4 = 0.911 ?0.020; a&["11, •22] = 0.0161, 95% CI = -0.0309 to 0.0631), and recapture rates (p = 0.097 + 0.016) of banded and radiomarked individuals were not different (&[Pradioed, Pbandedl = 0.145, 95% CI = -0.510 to 0.800).Combining these data types in a common model resulted in more precise estimates of movement and recapture rates than separate estimation, but ability to detect stratum or mark-specific differences in parameters was weak.We conducted simulation trials to investigate the effects of varying study designs on parameter accuracy and statistical power to detect important differences.Parameter accuracy was high (relative bias [RBIAS] <2%) and confidence interval coverage close to nominal, except for survival estimates of banded birds for the "off study area" stratum, which were negatively biased (RBIAS -7 to -15%) when sample sizes were small (5-10 banded or radioed animals "released" per time interval).To provide adequate data for useful inference from this model, study designs should seek a minimum of 25 animals of each marking type observed (marked or observed via telemetry) in each time period and geographic stratum.
Landscapes in agricultural systems continue to undergo significant change, and the loss of biodiversity is an ever-increasing threat. Although habitat restoration is beneficial, management actions do not always result in the desired outcome. Managers must understand why management actions fail; yet, past studies have focused on assessing habitat attributes at a single spatial scale, and often fail to consider the importance of ecological mechanisms that act across spatial scales. We located survey sites across southern Nebraska, USA and conducted point counts to estimate Ring-necked Pheasant abundance, an economically important species to the region, while simultaneously quantifying landscape effects using a geographic information system. To identify suitable areas for allocating limited management resources, we assessed land cover relationships to our counts using a Bayesian binomial-Poisson hierarchical model to construct predictive Species Distribution Models of relative abundance. Our results indicated that landscape scale land cover variables severely constrained or, alternatively, facilitated the positive effects of local land management for Ring-necked Pheasants.
We monitored adult and juvenile breeding-season movements and habitat use of radio-tagged Wood Thrushes (Hylocichla mustelina) at the Piedmont National Wildlife Refuge, central Georgia, USA. We investigated the effects that management for Red-cockaded Woodpeckers (Picoides borealis), thinning and burning >30 year old loblolly pine (Pinus taeda) habitat, had on Wood Thrushes, a ground-foraging and midstory-nesting species. Adult Wood Thrush pairs regularly moved long distances between nesting attempts (range 1 to 17,388 m). The only experimental effect we found on adult movements was a decrease in weekly emigration rates (Ψ) from thinned and burned compartments after silvicultural management. Adult males preferred riparian hardwoods with sparse to moderate cover and those preferences increased following management. Juveniles remained near their nest site (x̄ = 177 m, SE = 113) for an average 24 days (SE = 6.3), and then dispersed a mean 2,189 m (SE = 342). Before dispersal, juveniles preferred upland hardwood–pine mixed habitat (P < 0.05) with moderate overstory cover (P < 0.05). We found no management effects on dispersal distances or predispersal habitat use. However, juveniles from thinned and burned compartments dispersed to hardwood habitats with dense cover, whereas birds from control compartments dispersed to pine-dominated habitats with sparse cover. All juveniles dispersed to areas with habitat similar to what they used before dispersal. Small-scale thinning and burning for Red-cockaded Woodpeckers may have had little effect on Wood Thrush habitat use and movements because typical movements were often larger than the scale (stand or compartment) targeted for management.
Quantifying patterns of nest survival is a first step toward understanding why birds decide when and where to breed. Most studies of nest survival have relied on generalized linear models (GLM) to explore these patterns. However, GLMs require assumptions about the models' structure that might preclude finding nonlinear patterns in survival data. Generalized additive models (GAM) provide a flexible alternative to GLMs for estimating linear and nonlinear patterns in data. Here we present a comparison of GLMs and GAMs for explaining variation in nest-survival data. We used two different model-selection criteria, the Bayes (BIC) and Akaike (AIC) information criteria, to select among simple and complex models. Our study was focused on the analysis of Redwinged Blackbird (Agelaius phoeniceus) nests in the Rainwater Basin wetlands of south-central Nebraska. Under BIC, our quadratic model of nest age had the most support, and the model predicted a concave pattern of daily nest survival. We found more model-selection uncertainty under AIC and found support for additive models with ordinal effects of both day and age. These models predicted much more temporal variation than did the linear models. Following our analysis, we discuss some of the advantages and disadvantages of GAMs. Despite the possible limitations of GAMs, our results suggest that they provide an efficient and flexible way to demonstrate nonlinear patterns in nest-survival data.
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