Browsing by Author "Buler, Jeffrey J."
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Item Artificial light at night is a top predictor of bird migration stopover density(Nature Communications, 2023-12-04) Horton, Kyle G.; Buler, Jeffrey J.; Anderson, Sharolyn J.; Burt, Carolyn S.; Collins, Amy C.; Dokter, Adriaan M.; Guo, Fengyi; Sheldon, Daniel; Tomaszewska, Monika Anna; Henebry, Geoffrey M.As billions of nocturnal avian migrants traverse North America, twice a year they must contend with landscape changes driven by natural and anthropogenic forces, including the rapid growth of the artificial glow of the night sky. While airspaces facilitate migrant passage, terrestrial landscapes serve as essential areas to restore energy reserves and often act as refugia—making it critical to holistically identify stopover locations and understand drivers of use. Here, we leverage over 10 million remote sensing observations to develop seasonal contiguous United States layers of bird migrant stopover density. In over 70% of our models, we identify skyglow as a highly influential and consistently positive predictor of bird migration stopover density across the United States. This finding points to the potential of an expanding threat to avian migrants: peri-urban illuminated areas may act as ecological traps at macroscales that increase the mortality of birds during migration.Item Autumn stopover hotspots and multiscale habitat associations of migratory landbirds in the eastern United States(Proceedings of the National Academy of Sciences, 2023-01-09) Guo, Fengyi; Buler, Jeffrey J.; Smolinsky, Jaclyn A.; Wilcove, David S.Significance: Understanding the en route habitat requirements of migratory birds is critical for conservation but difficult to know at a large scale. We mapped stopover density of landbirds during autumn migration for the eastern United States using radar data. At a coarse scale, we found that birds migrate across a relatively broad front, underscoring the importance of widespread, locally based conservation efforts. At finer scales, we identified stopover hotspots that consistently support high densities of migrants. We demonstrate that forests provide the most important habitats for autumn migrants and that deciduous forest fragments in heavily deforested regions support especially high densities of migrants. We also present evidence that the now-agriculture-dominated Midwest constitutes an inland migration barrier for forest birds. Abstract: Halting the global decline of migratory birds requires a better understanding of migration ecology. Stopover sites are a crucial yet understudied aspect of bird conservation, mostly due to challenges associated with understanding broad-scale patterns of transient habitat use. Here, we use a national network of weather radar stations to identify stopover hotspots and assess multiscale habitat associations of migratory landbirds across the eastern United States during autumn migration. We mapped seasonal bird densities over 5 y (2015 to 2019) from 60 radar stations covering 63.2 million hectares. At a coarse scale, we found that landbirds migrate across a broad front with small differences in migrant density between radar domains. However, relatively more birds concentrate along the Mississippi River and Appalachian Mountains. At a finer scale, we identified radar pixels that consistently harbored high densities of migrants for all 5 y, which we classify as stopover hotspots. Hotspot probability increased with percent cover of all forest types and decreased with percent cover of pasture and cultivated crops. Moreover, we found strong concentrating effects of deciduous forest patches within deforested regions. We also found that the prairie biome in the Midwest (now mostly cropland) is likely a migration barrier, with large concentrations of migrants at the prairie–forest boundary after crossing the agricultural Midwest. Overall, the broad-front migration pattern highlights the importance of locally based conservation efforts to protect stopover habitats. Such efforts should target forests, especially deciduous forests in highly altered landscapes. These findings demonstrate the value of multiscale habitat assessments for the conservation of migratory landbirds.Item Effects of broadcasting calls during surveys to estimate density and occupancy of northern bobwhite(Wildlife Society Bulletin, 2012-03-23) Duren, Kenneth R.; Buler, Jeffrey J.; Jones, William L.; Williams, Christopher K.We assessed the effects of using a broadcast caller during surveys and increasing survey duration to estimate northern bobwhite (Colinus virginianus) density and occupancy. From 15 May 2009 to 15 August 2009, we conducted repeat-visit breeding bobwhite surveys at 180 sites in Delaware, USA. Increasing survey duration from 3 min to 7 min, or using a broadcast caller, improved detection probability for a single visit by 52% and 42%, respectively. However, density estimates when using a broadcast caller were biased high—≥3 times greater compared to passive-listening surveys. Density estimates for 3-min and 7-min passive surveys were not different. Additionally, bobwhite occupancy was similar among all 3 survey treatments. Use of a broadcast caller to survey for bobwhites appears to violate the assumption of distance sampling that an individual is detected prior to movement. Use of a broadcast caller is inappropriate for determining density estimates through distance sampling, but may be appropriate for determining site occupancy. © 2011 The Wildlife Society.Item Potential Effect of Low-Rise, Downcast Artificial Lights on Nocturnally Migrating Land Birds(Integrative and Comparative Biology, 2021-07-08) Cabrera-Cruz, Sergio A.; Larkin, Ronald P.; Gimpel, Maren E.; Gruber, James G.; Zenzal, Theodore J. Jr; Buler, Jeffrey J.Artificial light at night (ALAN) on tall or upward-pointed lighting installations affects the flight behavior of night-migrating birds. We hypothesized that common low-rise lights pointing downward also affect the movement of nocturnal migrants. We predicted that birds in flight will react close to low-rise lights, and be attracted and grounded near light sources, with a stronger effect on juveniles during their autumn migration. We conducted a controlled longitudinal experiment with light-emitting diode floodlights and considered nearby structures that turn on lights at night. We analyzed 1501 high-resolution 3D nocturnal flight paths of free-flying migrants and diurnally captured 758–2009 birds around experimental lights during spring and autumn 2016, and spring 2017. We identified change points along flight paths where birds turned horizontally or vertically, and we considered these indicative of reactions. Flight paths with and without reactions were generally closer to our experimental site in spring than in autumn when the lights were on. Reactions were up to 40% more likely to occur in autumn than in spring depending on the threshold magnitude of turning angle. Reactions in spring were up to ∼60% more likely to occur at ∼35 m from the lights than at >1.5 km. In autumn, some vertical reactions were ∼40% more likely to occur at ∼50 m from the lights than at >2.2 km. Interactions between distance to lights and visibility or cloud cover were consistent with known effects of ALAN on nocturnal migrants. Under poor visibility, reactions were up to 50% more likely to occur farthest from structures in spring, but up to 60% more likely to occur closest to lights in autumn. Thus, the effects of ALAN on night-migrating land birds are not limited to bright lights pointing upward or lights on tall structures in urban areas. Diurnal capture rates of birds were not different when lights were on or off for either season. To our knowledge, this is the first study to show that low-rise lights pointing downward affect night-migrating birds. Although the interpreted reactions constitute subtle modifications in the linearity of flight paths, we discuss future work that could verify whether the protection of nocturnal migrants with lights-out programs would have greater impact if implemented beyond urban areas and include management of low-rise lights.Item Seasonal patterns and protection status of stopover hotspots for migratory landbirds in the eastern United States(Current Biology, 2024-01-22) Guo, Fengyi; Buler, Jeffrey J.; Smolinsky, Jaclyn A.; Wilcove, David S.Summary Migratory landbirds in North America are experiencing dramatic population declines. Although considerable research and conservation attention have been directed toward these birds’ breeding and wintering grounds, far less is known about the areas used as stopover sites during migration. To address this knowledge gap, we used 5 years of weather surveillance radar data to map seasonal stopover densities of landbirds across the eastern United States during spring and autumn migration. We identified stopover hotspots covering 2.47 million ha that consistently support high densities of migratory landbirds in spring or autumn. However, only 16.7% of these sites are hotspots in both seasons. The distribution of hotspots is shifted eastward in autumn compared with spring. Deciduous forest is the most important habitat type in both seasons, with deciduous forest fragments embedded in broadly deforested regions having the highest probability of being hotspots. The concentration of birds in these forest fragments is stronger in spring, especially in the agricultural Midwest. We found generally higher stopover densities in protected areas than in unprotected areas in both seasons. Nonetheless, only one-third of identified stopover hotspots have some sort of protected status, and more than half of these protected hotspots are subject to extractive uses. A well-distributed network of well-protected stopover areas, complementing conservation efforts on the breeding and wintering grounds, is essential to sustaining healthy populations of migratory landbirds in North America.Item Using weather radar to help minimize wind energy impacts on nocturnally migrating birds(Conservation Letters, 2022-05-02) Cohen, Emily B.; Buler, Jeffrey J.; Horton, Kyle G.; Lodd, Scott R.; Cabrera-Cruz, Sergio A.; Smolinsky, Jaclyn A.; Marra, Peter P.As wind energy rapidly expands worldwide, information to minimize impacts of this development on biodiversity is urgently needed. Here we demonstrate how data collected by weather radar networks can inform placement and operation of wind facilities to reduce collisions and minimize habitat-related impacts on nocturnally migrating birds. We found over a third of nocturnal migrants flew through altitudes within the rotor-swept zone surrounding the North American Great Lakes, a continentally important migration corridor. Migrating birds concentrated in terrestrial stopover habitats within 20-km from shorelines, a distance well beyond the current guidelines for construction of new land-based facilities, and their distributions varied seasonally and at local and regional scales, creating predictable opportunities to minimize impacts from wind energy development and operation. Networked radar data are available across the United States and other countries and broad application of this approach could provide information critical to bird-friendly expansion of this globally important energy source.