Migratory birds like endangered whooping cranes (Grus americana) require suitable nocturnal roost sites during twice annual migrations. Whooping cranes primarily roost in shallow surface water ...wetlands, ponds, and rivers. All these features have been greatly impacted by human activities, which present threats to the continued recovery of the species. A portion of one such river, the central Platte River, has been identified as critical habitat for the survival of the endangered whooping crane. Management intervention is now underway to rehabilitate habitat form and function on the central Platte River to increase use and thereby contribute to the survival of whooping cranes. The goal of our analyses was to develop habitat selection models that could be used to direct riverine habitat management activities (i.e., channel widening, tree removal, flow augmentation, etc.) along the central Platte River and throughout the species' range. As such, we focused our analyses on two robust sets of whooping crane observations and habitat metrics the Platte River Recovery Implementation Program (Program or PRRIP) and other such organizations could influence. This included channel characteristics such as total channel width, the width of channel unobstructed by dense vegetation, and distance of forest from the edge of the channel and flow-related metrics like wetted width and unit discharge (flow volume per linear meter of wetted channel width) that could be influenced by flow augmentation or reductions during migration. We used 17 years of systematic monitoring data in a discrete-choice framework to evaluate the influence these various metrics have on the relative probability of whooping crane use and found the width of channel unobstructed by dense vegetation and distance to the nearest forest were the best predictors of whooping crane use. Secondly, we used telemetry data obtained from a sample of 38 birds of all ages over the course of seven years, 2010-2016, to evaluate whooping crane use of riverine habitat within the North-central Great Plains, USA. For this second analysis, we focused on the two metrics found to be important predictors of whooping crane use along the central Platte River, unobstructed channel width and distance to nearest forest or wooded area. Our findings indicate resource managers, such as the Program, have the potential to influence whooping crane use of the central Platte River through removal of in-channel vegetation to increase the unobstructed width of narrow channels and through removal of trees along the bank line to increase unforested corridor widths. Results of both analyses also indicated that increases in relative probability of use by whooping cranes did not appreciably increase with unobstructed views ≥200 m wide and unforested corridor widths that were ≥330 m. Therefore, managing riverine sites for channels widths >200 m and removing trees beyond 165 m from the channel's edge would increase costs associated with implementing management actions such as channel and bank-line disking, removing trees, augmenting flow, etc. without necessarily realizing an additional appreciable increase in use by migrating whooping cranes.
Full text
Available for:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Wildlife species confront threats from climate and land use change, exacerbating the influence of extreme climatic events on populations and biodiversity. Migratory waterbirds are especially ...vulnerable to hydrological drought via reduced availability of surface water habitats. We assessed how whooping cranes (Grus americana) modified habitat use and migration strategies during drought to evaluate their resilience to changing conditions and adaptive capacity. We categorized >8000 night‐roost sites used by 146 cranes from 2010 to 2022 and examined relative use during non‐drought, moderate drought, and extreme drought conditions. We found cultivated and uncultivated palustrine and lacustrine wetlands were generally used less during droughts than non‐drought conditions. Conversely, impounded palustrine and lacustrine systems and rivers served more frequently as drought refugia (i.e., used more during drought than non‐drought conditions). Night roosts occurred primarily on private lands (86% overall); public land use decreased with latitude and increased with drought severity, with greatest use (56%) occurring during severe autumn drought in the southern Great Plains. Quantifying use of identified critical habitats in the United States indicated that Cheyenne Bottoms State Waterfowl Management Area and Quivira National Wildlife Refuge were used less during drought, and the Central Platte River and Salt Plains National Wildlife Refuge received similar use during drought compared to non‐drought conditions. Our findings provide insights into compensatory use of habitats, where impounded surface water may function in a complementary fashion with natural wetlands. Collectively, these and other types of wetlands distributed across the migration corridor provided a reliable network of habitat available across the Great Plains. A diversity of wetlands available during variable environmental conditions would be useful in supporting continued recovery of whooping cranes and likely have benefits for a wide array of migratory birds.
Wildlife, particularly migratory waterbirds like whooping cranes, face increasing threats from climate change and land use shifts, especially during extreme weather events. Whooping cranes readily modified habitat use more so than migration patterns when encountering drought conditions. Regional patterns in habitat use shifts were evident but, overall, cultivated wetlands were used less and impounded wetlands and lakes used more during drought compared to non‐drought conditions. These findings underscore the importance of diverse wetland habitats in the Great Plains for supporting the recovery of whooping cranes and other migratory birds.
Full text
Available for:
FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Migratory birds use numerous strategies to successfully complete twice-annual movements between breeding and wintering sites. Context for conservation and management can be provided by characterizing ...these strategies. Variations in strategy among and within individuals support population persistence in response to changes in land use and climate. We used location data from 58 marked Whooping Cranes (Grus americana) from 2010 to 2016 to characterize migration strategies in the U.S. Great Plains and Canadian Prairies and southern boreal region, and to explore sources of heterogeneity in their migration strategy, including space use, timing, and performance. Whooping Cranes completed ∼3,900-km migrations that averaged 29 days during spring and 45 days during autumn, while making 11–12 nighttime stops. At the scale of our analysis, individual Whooping Cranes showed little consistency in stopover sites used among migration seasons (i.e. low site fidelity). In contrast, individuals expressed a measure of consistency in timing, especially migration initiation dates. Whooping Cranes migrated at different times based on age and reproductive status, where adults with young initiated autumn migration after other birds, and adults with and without young initiated spring migration before subadult birds. Time spent at stopover sites was positively associated with migration bout length and negatively associated with time spent at previous stopover sites, indicating Whooping Cranes acquired energy resources at some stopover sites that they used to fuel migration. Whooping Cranes were faithful to a defined migration corridor but showed less fidelity in their selection of nighttime stopover sites; hence, spatial targeting of conservation actions may be better informed by associations with landscape and habitat features rather than documented past use at specific locations. The preservation of variation in migration strategies existing within this species that experienced a severe population bottleneck suggests that Whooping Cranes have maintained a capacity to adjust strategies when confronted with future changes in land use and climate.
The central Platte River in Nebraska, USA, has undergone substantial channel narrowing since basin settlement in the mid-nineteenth century. Many researchers have studied the causes of channel ...narrowing and its implications for endangered species that use wide, shallow channel segments with barren sandbars. As a result, changes in metrics such as unvegetated channel width have been studied. With few exceptions, these measures are estimated from aerial imagery without mention of error in relation to actual channel conditions and/or investigator bias. This issue is not unique to central Platte River studies, as a general lack of commentary is apparent regarding the direct comparison of channel planform characteristics interpreted from aerial imagery relative to those measured in the field. Here we present a case study where data collected by the Platte River Recovery Implementation Program was used to make multiple comparisons using three years of field-measured unvegetated channel widths and those photointerpreted from aerial imagery. Widths were interpreted by three investigators, who identified similar widths in almost all cases. Photointerpretation from imagery collected during the fall resulted in unvegetated width estimates that were more consistent with field measurments than estimates derived using imagery collected in June. Differences were attributed to three main factors: (1) influences of discharge on photointerpretation of unvegetated channel width; (2) increases in vegetative cover throughout the growing season; and (3) resolution of imagery. Most importantly, we concluded that photointerpretation of unvegetated widths from imagery collected during high flows can result in significant over estimation of unvegetated channel width.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Collisions with anthropogenic structures by long-distance migrants and threatened and endangered species are a growing global conservation concern. Increasing the visibility of these structures may ...reduce collisions but may only be accepted by local residents if it does not create a visual disturbance. Recent research has shown the potential for ultraviolet (UV) light, which is nearly imperceptible to humans, to mitigate avian collisions with anthropogenic structures. We tested the effectiveness of two UV (390–400 nm) Avian Collision Avoidance Systems (ACASs) at reducing collisions at two 260-m spans of marked power lines at the Iain Nicolson Audubon Center at Rowe Sanctuary, an important migratory bird stopover location in Nebraska. We used a randomized design and a tiered model selection approach employing generalized linear models and the Akaike Information Criterion to assess the effectiveness of ACASs considering environmental (e.g., precipitation) and detection probability (e.g., migration chronology) variables. We found focal (assessed power line) and distal (neighboring power line) ACAS status and environmental variables were important predictors of avian collisions. Our top model suggests that the focal ACAS illumination reduced collisions by 88%, collisions were more likely at moderate (10–16 km/h) compared to lower or higher wind speeds, and collision frequency decreased with precipitation occurrence. Our top model also indicates that the distal ACAS illumination reduced collisions by 39.4% at the focal power line when that ACAS was off, suggesting a positive "neighbor effect" of power line illumination. Although future applications of ACASs would benefit from additional study to check for potential negative effects (for example, collisions involving nocturnal foragers such as bats or caprimulgiform birds drawn to insects), we suggest that illuminating power lines, guy wires, towers, wind turbines, and other anthropogenic structures with UV illumination will likely lower collision risks for birds while increasing human acceptance of mitigation measures in urban areas.
Predicting a species' distribution can be helpful for evaluating management actions such as critical habitat designations under the U.S. Endangered Species Act or habitat acquisition and ...rehabilitation. Whooping Cranes (Grus americana) are one of the rarest birds in the world, and conservation and management of habitat is required to ensure their survival. We developed a species distribution model (SDM) that could be used to inform habitat management actions for Whooping Cranes within the state of Nebraska (U.S.A.). We collated 407 opportunistic Whooping Crane group records reported from 1988 to 2012. Most records of Whooping Cranes were contributed by the public; therefore, developing an SDM that accounted for sampling bias was essential because observations at some migration stopover locations may be under represented. An auxiliary data set, required to explore the influence of sampling bias, was derived with expert elicitation. Using our SDM, we compared an intensively managed area in the Central Platte River Valley with the Niobrara National Scenic River in northern Nebraska. Our results suggest, during the peak of migration, Whooping Crane abundance was 262.2 (90% CI 40.2–3144.2) times higher per unit area in the Central Platte River Valley relative to the Niobrara National Scenic River. Although we compared only 2 areas, our model could be used to evaluate any region within the state of Nebraska. Furthermore, our expert-informed modeling approach could be applied to opportunistic presence-only data when sampling bias is a concern and expert knowledge is available. Predecir la distribución de una especie puede ser útil para la evaluación de las acciones de manejo, como la designación de hábitats críticos bajo el Acta Estadunidense de Especies. Amenazadas o la adquisición y rehabilitación de hábitats. La grulla trompetera (Grus americana) es una de las aves más raras en el mundo y la conservación y el manejo de hábitat son requeridos para asegurar su supervivencia. Desarrollamos un modelo de distribución de especies (MDE) que podría usarse para informar a las acciones de manejo de hábitat de esta grulla dentro del estado de Nebraska (E.U.A). Cotejamos 407 registros oportunistas de grupos de grullas trompeteras, reportados desde 1998 hasta 2012. La mayoría de estos registros fueron contribuidos por el público, por lo que fue esencial desarrollar un MDE que explicara el sesgo de muestreo, ya que las observaciones en algunas localidades de escala migratoria podrían estar sub-representadas. Un conjunto auxiliar de datos, requerido para explorar la influencia del sesgo de muestro, fue obtenido con información de expertos. Con el uso de nuestro MDE, comparamos un área de manejo intensivo en el Valle del Río Platte Central con el Río Escénico Niobrara en el norte de Nebraska. Nuestros resultados sugieren que durante el pico de la migración, la abundancia de la grulla trompetera fue 262.2 (90% IC 40.2. 3144-2) veces más alta por unidad de área en el Valle del Río Platte Central en relación con el Río Escénico Niobrara. Aunque sólo comparamos dos áreas, nuestro modelo podría usarse para evaluar cualquier región dentro del estado de Nebraska. Más allá, nuestra estrategia de modelado informado por expertos podría aplicarse a los datos que representan únicamente a la presencia oportunista cuando el sesgo de muestreo es un motivo de preocupación y el conocimiento de expertos está disponible.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NMLJ, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
Summary
Species distribution models (SDMs) for presence‐only data depend on accurate and precise measurements of geographical and environmental covariates that influence presence and abundance of the ...species. Some data sets, however, may contain both systematic and random errors in the recorded location of the species. Environmental covariates at the recorded location may differ from those at the true location and result in biased parameter estimates and predictions from SDMs.
Regression calibration is a well‐developed statistical method that can be used to correct the bias in estimated coefficients and predictions from SDMs when the recorded geographical location differs from the true location for some, but not all locations. We expand the application of regression calibration methods to SDMs and provide illustrative examples using simulated data and opportunistic records of whooping cranes (Grus americana).
We found we were able to successfully correct the bias in our SDM parameters estimated from simulated data and opportunistic records of whooping cranes using regression calibration.
When modelling species distributions with data that have geographical location errors, we recommend researchers consider the effect of location errors. Correcting for location errors requires that at least a portion of the data have locations recorded without error. Bias correction can result in an increase in variance; this increase in variance should be considered when evaluating the utility of bias correction.
Full text
Available for:
FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Available stopover habitats with quality foraging opportunities are essential for migrating waterbirds, including Whooping Crane (Grus americana). Several studies have evaluated habitats used by ...Whooping Crane for roosting throughout its migration corridor; however, habitats associated with foraging and other diurnal activities have received less attention. We used data collected from 42 Whooping Crane individuals that included 2169 diurnal use locations within 395 stopover sites evaluated during spring 2013 to fall 2015 to assess diurnal habitat selection throughout the U.S. portion of the migration corridor. We found that Whooping Crane selected wetland land-cover types (i.e., open water, riverine, and semipermanent wetlands) and lowland grasslands for diurnal activities over all other land-cover types that we evaluated, including croplands. Whooping Crane generally avoided roads, and avoidance varied based on land-cover class. There has been considerable alteration and destruction of natural wetlands and rivers that serve as roosting and foraging sites for migrating Whooping Crane. Given recent droughts and the likelihood of future landscape changes within the migration corridor, directing conservation efforts toward protecting and enhancing wetland stopover areas may prove critical for continued growth of the last remaining wild population of Whooping Crane. Future studies of this Whooping Crane population should focus on specific wetland complexes and riverine sites throughout the migration corridor to identify precise management actions that could be taken to enhance and protect these imperilled land-cover types.
A portion of the Aransas-Wood Buffalo population of Whooping Cranes (Grus americana) stopover within the Central Platte River Valley (CPRV) annually. Past studies have found Whooping Cranes select ...herbaceous wetlands over agricultural fields when evaluated at a migration-corridor scale. However, recent studies conducted within the CPRV have reported Whooping Cranes selected agricultural fields and avoided herbaceous landcover classes. We hypothesized that much of this discrepancy was due to differences in landcover classifications used in previous studies, particularly those related to wetland designations. We used multiple existing, fine-scale geospatial data sources considering both landcover and hydrological factors to define unique and regionally specific ecotopes, which are the smallest homogenous and biologically relevant mappable units of analysis in landscape ecology (e.g., meadow-marsh, upland agriculture, etc.). We examined whether ecotope-based landcover, when evaluated at multiple spatial scales (i.e., 400 m and 1000 m), predicted terrestrial Whooping Crane occurrence within the CPRV. We used generalized linear mixed models within an information-theoretic approach to assess Whooping Crane occurrence within the CPRV. We found distinct ecotopes at the 1000-m scale explained nearly 40% of the variation in Whooping Crane occurrence. Ecotope models outperformed models including only their component parts such as flooding frequency and wetland designation. Whooping Cranes occurred more frequently within wetland portions of both agricultural fields and natural herbaceous communities and were less likely to use analogous upland components. We also found that occurrence was positively associated with proximity to the main channel of the Platte River and that Whooping Cranes avoided roads and developed areas, as several other studies have reported. Our findings indicate herbaceous and agricultural wetland areas should be targeted for Whooping Crane conservation efforts within the CPRV and perhaps regionally.
The Platte River Recovery Implementation Program (PRRIP) and its partners invested substantial resources in creating and managing off-channel nesting habitat for Interior Least Terns (Sternula ...antillarum athalassos) and Piping Plovers (Charadrius melodus) along the central Platte River in Nebraska. Among other things, management activities implemented at nesting sites to increase nest and brood survival have included tree removal, construction of a water barrier surrounding the nesting areas, installation of predator fences, and predator trapping. We used 15 years of data at off-channel sites along the central Platte River to assess the influence of several biotic and abiotic variables on the survival of Interior Least Tern and Piping Plover nests and broods. We observed high survival rates for Interior Least Tern and Piping Plover nests and broods as two-thirds of Interior Least Tern and three-quarters of Piping Plover nests were successful and three-quarters of all Interior Least Tern and Piping Plover broods were successful. We found productivity of Interior Least Terns and Piping Plovers was reduced during both the nesting and brood-rearing stages by weather-related variables rather than variables the PRRIP can manage. As such, we conclude habitat management activities implemented at off-channel sites to date are sufficient for maintaining high levels of productivity for Interior Least Terns and Piping Plovers along the central Platte River.
PDF
