Lack of standardization in the use of road counts for surveying raptors
Abstract Examination of population trends for raptors is a research priority, especially given recent concern for their conservation status. Road counts—in which raptors are counted from a motorized vehicle moving along the ground—might be an effective method to expand the monitoring of raptor populations and estimation of trends. Here, we review past methods used to perform road counts of raptors and present revised recommendations to aid collaboration, data transfer, and interpretation of results across monitoring programs. We performed a standardized keyword search of online literature databases to obtain 148 past road count studies. The number of studies employing road counts increased per year since the 1970s. Most of these studies occurred in North America. The times of day during which road counts were conducted ranged from sunrise to sunset, and maximum speeds ranged from 10 to 113 km hr–1. The number of observers ranged from 1 (the driver) to 5. Most (93) of the studies used unlimited-width transects and fixed-width transects ranging from 0.02 to 2.50 km wide. Sixteen percent of studies calculated or corrected for the probability of detection. Such broad variation in the methodology used during road counts, coupled with infrequent correction for detection, hampers the interpretation of results across road survey programs. We suggest that road count practitioners should emphasize the collection of data, such as speed, number of observers, and distance to observed raptors, which would allow for the calculation of detection-corrected estimates. Such correction would likely improve trend estimation. Recent technology, including mobile apps, allows researchers to collect such data relatively easily, conducting their own studies while contributing to a broader raptor monitoring initiative. Road counts will likely become more useful as statistical analysis of road count data improves and researchers pool their data in a global effort to monitor raptors.
- The Condor
- Citations: 7
- Jan 5, 2021
Migratory status determines resource selection by American Woodcock at an important fall stopover, Cape May, New Jersey
Abstract Migration is a period of high activity and exposure during which risks and energetic demand on individuals may be greater than during nonmigratory periods. Stopover locations can help mitigate these threats by providing supplemental energy en route to the animal’s end destination. Effective conservation of migratory species therefore requires an understanding of use of space that provides resources to migratory animals at stopover sites. We conducted a radio-telemetry study of a short-distance migrant, the American Woodcock (Scolopax minor), at an important stopover site, the Cape May Peninsula, New Jersey. Our objectives were to describe land-cover types used by American Woodcock and evaluate home range habitat selection for individuals that stopover during fall migration and those that choose to overwinter. We radio-marked 271 individuals and collected 1,949 locations from these birds (0–21 points individual–1) over 4 yr (2010 to 2013) to inform resource selection functions of land-cover types and other landscape characteristics by this species. We evaluated these relationships at multiple spatial extents for (1) birds known to have ultimately left the peninsula (presumed migrants), and (2) birds known to have remained on the peninsula into the winter (presumed winter residents). We found that migrants selected deciduous wetland forest, agriculture, mixed shrub, coniferous wetland forest, and coniferous shrub, while wintering residents selected deciduous wetland forest, coniferous shrub, and deciduous shrub. We used these results to develop predictive models of potential habitat: 7.80% of the peninsula was predicted to be potential stopover habitat for American Woodcock (95% classification accuracy) and 4.96% of the peninsula was predicted to be potential wintering habitat (85% classification accuracy). Our study is the first to report habitat relationships for migratory American Woodcock in the coastal U.S. and provides important spatial tools for local and regional managers to support migratory and winter resident woodcock populations into the future.
- The Condor
- Citations: 1
- Dec 31, 2020
North American Breeding Bird Survey status and trend estimates to inform a wide range of conservation needs, using a flexible Bayesian hierarchical generalized additive model
Abstract The status and trend estimates derived from the North American Breeding Bird Survey (BBS) are critical sources of information for bird conservation. However, the estimates are partly dependent on the statistical model used. Therefore, multiple models are useful because not all of the varied uses of these estimates (e.g., inferences about long-term change, annual fluctuations, population cycles, and recovery of once-declining populations) are supported equally well by a single statistical model. Here we describe Bayesian hierarchical generalized additive models (GAMs) for the BBS, which share information on the pattern of population change across a species’ range. We demonstrate the models and their benefits using data from a selection of species, and we run full cross-validation of the GAMs against 2 other models to compare the predictive fit. The GAMs have a better predictive fit than the standard model for all species studied here and comparable predictive fit to an alternative first difference model. In addition, one version of the GAM described here (GAMYE) estimates a population trajectory that can be decomposed into a smooth component and the annual fluctuations around that smooth component. This decomposition allows trend estimates based only on the smooth component, which are more stable between years and are therefore particularly useful for trend-based status assessments, such as those by the International Union for the Conservation of Nature. It also allows for the easy customization of the model to incorporate covariates that influence the smooth component separately from those that influence annual fluctuations (e.g., climate cycles vs. annual precipitation). For these reasons and more, this GAMYE model is a particularly useful model for the BBS-based status and trend estimates.
- The Condor
- Citations: 8
- Dec 26, 2020
Habitat ecology of Nearctic–Neotropical migratory landbirds on the nonbreeding grounds
Abstract Of the approximately 716 bird species that breed in North America, 386 (54%) are considered Nearctic–Neotropical migrants by the U.S. Fish and Wildlife Service. In the past 50 yr, scores of these migratory species, including some once considered common, have declined dramatically. Nearctic–Neotropical migrants normally spend 6–8 months in tropical habitats, making the identification, availability, and management of Neotropical habitats critical issues for their conservation. Yet, for most species, complete and nuanced information about their use of tropical habitats and the relative effects of breeding vs. wintering conditions on survival, productivity, and population trends is not available, though many studies point to Neotropical overwintering habitats as being a strong driver of population change. Particularly important for long-distance Nearctic–Neotropical migrants is an understanding of how “carry-over effects” arise and influence population trends when conditions on wintering grounds and tropical stopover areas affect subsequent reproductive performance on breeding grounds. For example, why some species show strong carry-over effects from tropical habitats while others do not is not fully understood. In recent years, many studies have offered insights into these issues by taking advantage of new scientific methods and technological innovations. In this review, we explore threats facing North American breeding birds that migrate to the Neotropics, summarize knowledge of habitat selection and use on the wintering grounds, describe how conditions at one point in the annual cycle may manifest in subsequent seasons or life history stages, and discuss conservation concerns such as climate change and the potential for phenological mismatch.
- The Condor
- Citations: 15
- Oct 14, 2020
Advancing scientific knowledge and conservation of birds through inclusion of conservation social sciences in the American Ornithological Society
Abstract Conservation efforts are shaped by individual and collective human behaviors, cultural norms and values, economic pressures, and political and organizational structures. As such, the conservation social sciences—disciplines that draw on social science theories and approaches to improve conservation efforts—can play a vital role in advancing the science and practice of bird conservation. We connect the rich, ongoing discussion about the vital role of the conservation social sciences to the specific context of bird conservation and make an argument for the importance of proactive inclusion of these sciences in ornithological societies. First, we introduce the conservation social sciences and illustrate how they can improve the design and implementation of conservation programs and policies for birds. Drawing on discussions from a symposium we organized at the 2019 American Ornithological Society (AOS) annual meeting, we encourage the AOS to make institutional changes that could further support the inclusion of conservation social sciences. These changes ideally would include a working group, conference plenaries and themes, and high-quality social science publications, along with support and encouragement for ornithologists and bird conservationists to partake in trainings and collaborate with social scientists. Strategies for how to do so effectively can be adapted from other conservation societies that have paved the way for disciplinary inclusivity.
- The Condor
- Citations: 10
- Oct 5, 2020