One of the greatest challenges to informed conservation of migratory animals is elucidating spatiotemporal variation in distributions. Without such information, it is impossible to understand full-annual-cycle ecology and effectively implement conservation actions that address where and when populations are most limited. We deployed and recovered light-level geolocators (n = 34) at 6 breeding sites in North America across the breeding range of a declining long-distance migratory bird, the Prothonotary Warbler (Protonotaria citrea). We sought to determine migratory routes, stopover location and duration, and the location of overwintering grounds. We found that the species exhibits a large-scale, east‒west split in migratory routes and weak migratory connectivity across its range. Specifically, almost all individuals, regardless of breeding origin, overlapped in their estimated wintering location in northern Colombia, in an area 20% the size of the breeding range. Additionally, most of the individuals across all breeding locations concentrated in well-defined stopover locations in Central America while en route to Colombia. Although error inherent in light-level geolocation cannot be fully ruled out, surprisingly much of the estimated wintering area included inland areas even though the Prothonotary Warbler is considered a specialist on coastal mangroves in winter. Based on these results, conservation efforts directed at very specific nonbreeding geographical areas will potentially have benefits across most of the breeding population. Our findings highlight the importance of using modern technologies to validate assumptions about little-studied portions of a species’ annual cycle, and the need to distribute sampling across its range.

Climate change is predicted to impact tropical mangrove forests due to decreased rainfall, sea‐level rise, and increased seasonality of flooding. Such changes are likely to influence habitat quality for migratory songbirds occupying mangrove wetlands during the tropical dry season. Overwintering habitat quality is known to be associated with fitness in migratory songbirds, yet studies have focused primarily on territorial species. Little is known about the ecology of nonterritorial species that may display more complex movement patterns within and among habitats of differing quality. In this study, we assess within‐season survival and movement at two spatio‐temporal scales of a nonterritorial overwintering bird, the prothonotary warbler (Protonotaria citrea), that depends on mangroves and tropical lowland forests. Specifically, we (a) estimated within‐patch survival and persistence over a six‐week period using radio‐tagged birds in central Panama and (b) modeled abundance and occupancy dynamics at survey points throughout eastern Panama and northern Colombia as the dry season progressed. We found that site persistence was highest in mangroves; however, the probability of survival did not differ among habitats. The probability of warbler occupancy increased with canopy cover, and wet habitats were least likely to experience local extinction as the dry season progressed. We also found that warbler abundance is highest in forests with the tallest canopies. This study is one of the first to demonstrate habitat‐dependent occupancy and movement in a nonterritorial overwintering migrant songbird, and our findings highlight the need to conserve intact, mature mangrove, and lowland forests.

Estimates of migratory connectivity are needed for full annual cycle population models of migratory bird species experiencing rapid declines in abundance. One technique to determine migratory connectivity is through stable isotope analysis. This low-resolution method may be influenced by how data are calibrated between isotopes measured in precipitation and those measured in feathers, and can be informed by incorporating relative abundance into the assignment model. eBird abundance maps are a new tool combining citizen science data into a predictive species distribution model. In the Prothonotary Warbler (Protonotaria citrea), a wetland-associated songbird with a patchy breeding distribution, we sought to use stable-hydrogen isotope analysis informed by a species-specific calibration equation and eBird abundance data to determine the strength of migratory connectivity. We developed a species-specific calibration equation using known-origin samples from the breeding grounds and found that stable-hydrogen isotope values measured in precipitation explained 50% of the variation in stable-hydrogen isotope values among feathers. We found that the assignment model incorporating eBird abundance data correctly identified the true origins of 66% of individuals, and that the average assignment area (as a measure of precision) was 64% of the breeding distribution. These results represented a 7% increase in precision and a 3% decrease in accuracy when compared to a model that was not informed by abundance. Based on these models, wintering populations from 6 countries represented a mix of likely breeding origins, suggesting low migratory connectivity for Prothonotary Warblers. We found evidence that wintering latitude was related to likely breeding origin, with individuals at western wintering locations more likely to have southern breeding origins, but this relationship was weak. These results corroborate studies using archival light-level geolocators and high-resolution genetic markers, which also demonstrated weak migratory connectivity in this species. For patchily distributed species, eBird abundance data may not provide a useful increase in precision and accuracy for isotope assignments.

SummaryThe status of range resources is not being adequately portrayed to the Agency, Department, Congress, or constituent groups by the existing methods of measuring range management. The measures traditionally used have been range condition and numbers of animal unit months (AUMs) of livestock grazing. Range condition is slow to change, often taking decades; and the number of AUMs of authorized grazing does not accurately reflect the work being accomplished on the ground.These problems are further complicated by effective range resources management creating a flow of outputs that go beyond those traditionally associated with range programs. Multiple products flow from range management, yet traditional budget and accounting constraints force separation of the benefits and costs into functional program areas. Legislation and General Accounting Office (GAO) reports have emphasized integrated resource management and the need to consider all outputs in resource decisionmaking.The Range Measurement Task Group of Agency personnel was assembled in January 1988 to evaluate and recommend methods of measurement that would best reflect the various jobs involved in managing range 'vegetation resources--their ecological status and interrelations. The overriding principle guiding the effort was that range management is broader than mere livestock grazing. Recreation, water quality and quantity, soil stability, wildlife habitat, and timber are other outputs associated with range management. Measurements of all products are needed to accurately describe the range program when budget decisions, project selections, and program justifications are prepared.The Range Measurement Task Group recommended that the tasks and outputs of range managers be summarized in five broad areas. Each area has methods of measuring that are useful in assessing progress toward goals and relating the area's status. The five areas are range vegetation management, riparian vegetation management, grazing management, noxious weed management, and wild horse and burro management. Separating riparian vegetation is done only to put emphasis on that portion of range vegetation. Managing and monitoring range resources require tracking many elements other than those highlighted here; however, these five have been identified for reports to the National level. Regions, National Forests, and Ranger Districts can use additional measures as necessary.In the task group proposal, vegetation management objectives of Forest plans are the yardsticks for measuring the effectiveness of range vegetation management. Measurements are in acres and describe whether range vegetation is being managed to meet Forest plan objectives: A similar measure is used for riparian vegetation. Noxious weed management is measured in acres treated or untreated and is reported annually. A status report showing the acres of infestation is suggested at 5-year intervals. Grazing management measures will reflect the status of allotment management plans being used to meet Forest plan objectives. Stat...