Geology topics

Kenneth V. Jacobson

Publications and source records attributed to Kenneth V. Jacobson.

4 recordsLinked to original sources

USGS2025

Using integrated step-selection analyses to map high-risk electrocution areas for a highly mobile species

Knowledge of animal-movement patterns is a crucial component in identifying areas with high potential for human–wildlife conflict and in prioritizing associated management actions. Electrical energy infrastructure is a major source of mortality for animals worldwide, with millions of birds colliding with or being electrocuted by power lines and power-pole infrastructure each year. Movement, habitat use, and the spatial distribution of electrocution risk can vary with age, but studies of younger age classes are often hampered because these groups are difficult to observe and lack well-defined home ranges. To identify movement patterns and high-use areas of bald eagles in Arizona, USA, we analyzed global positioning system (GPS) telemetry data collected from 13 immature bald eagles ( Haliaeetus leucocephalus ) across Arizona between 2017 and 2023. We built multi-scale, integrated step-selection functions that evaluated eagle responses to a suite of environmental covariates. We then used these models to simulate eagle movement and predict habitat use within and surrounding Maricopa County, which contains both the Phoenix Metropolitan Area and the plurality of bald eagle breeding areas in Arizona. We provide a use case for how these simulated movements could be used by resource managers to identify high-risk areas for electrocution. Eagles avoided urban areas and selected steeper slopes, more pronounced ridges, and areas with greater water and wetland land cover. Predicted habitat use by bald eagles was greatest near waterbodies and along ridges and steep slopes, and indicated where power infrastructure may pose greater electrocution risk. We show how integrated step-selection analyses and movement path simulation may be used for subadult animals lacking stable home ranges to predict high-use areas and identify locations with greater potential for negative human–wildlife interactions.

Arizona↗

USGS2025

Northward migrations of nonbreeding Bald Eagles from Arizona, USA.

Knowledge of the spatiotemporal patterns of migratory and nonbreeding-season movements by animals is critical for conservation, but can be difficult to obtain if animals move far from known breeding territories and across administrative and country borders. To understand the migratory movements of Bald Eagles ( Haliaeetus leucocephalus ) originating from a demographically closed population in Arizona, USA, we deployed GPS transmitters on 24 juveniles and 2 nonbreeding adult eagles between 2017 and 2023. We identified common migration routes, stopover locations, and migration phenology. Eagles moved north from Arizona during the population's post-breeding period in the boreal spring and summer, and returned south in autumn in advance of the breeding season. Eagles migrated along two primary routes: (1) along the Wasatch Mountains in Utah and extending into the Rocky Mountains of southern Idaho, and (2) through eastern Nevada and along the Rocky Mountains in western and northern Idaho. Stopover locations were frequently near lakes and rivers. Recent fledglings began migration later than older individuals and 15 of 16 of these juveniles that survived until the following breeding season returned to Arizona. The individual that did not return showed evidence of permanent emigration to northern California. Our results contribute to a growing understanding of avian migration routes within the Pacific Flyway and the diverse migration strategies, including northward migration following the breeding season, exhibited across raptor populations. We highlight that explicit studies of juveniles, subadults, and nonbreeding adults are key to understanding avian migration dynamics and identifying opportunities for conservation.

Arizona↗

USGS2024

Evaluating the effects of nest management on a recovering raptor using integrated population modeling

Evaluating population responses to management is a crucial component of successful conservation programs. Models predicting population growth under different management scenarios can provide key insights into the efficacy of specific management actions both in reversing population decline and in maintaining recovered populations. Bald eagle ( Haliaeetus leucocephalus ) conservation in the United States has seen many successes over the last 50 years, yet the extent to which the bald eagle population has recovered in Arizona, an important population within the Southwest region, remains an area of debate. Estimates of the species' population trend and an evaluation of ongoing nest-level management practices are needed to inform management decisions. We developed a Bayesian integrated population model (IPM) and population viability analysis (PVA) using a 36-year dataset to assess Arizona bald eagle population dynamics and their underlying demographic rates under current and possible future management practices. We estimated that the population grew from 77 females in 1993 to 180 females in 2022, an average yearly increase of 3%. Breeding sites that had trained personnel (i.e., nestwatchers) stationed at active nests to mitigate human disturbance had a 28% higher reproductive output than nests without this protection. Uncertainty around population trends was high, but scenarios that continued the nestwatcher program were less likely to predict abundance declines than scenarios without nestwatchers. Here, the IPM-PVA framework provides a useful tool both for estimating the effectiveness of past management actions and for exploring the management needs of a delisted population, highlighting that continued management action may be necessary to maintain population viability even after meeting certain recovery criteria.

Arizona↗

USGS2018

Prevalence and risk factors of Trichomonas gallinae and trichomonosis in golden eagle (Aquila chrysaetos) nestlings in western North America

Avian trichomonosis, caused by the protozoan Trichomonas gallinae , affects bird-eating raptors worldwide. Raptors can develop trichomonosis by feeding on infected prey, particularly Rock Pigeons (C olumba livia ), which are a reservoir for T. gallinae . Raptors may be particularly vulnerable to T. gallinae infection in degraded habitats, where changes in resources may cause raptors to switch from foraging on native prey to synanthropic avian species such as Rock Pigeons. Golden Eagles ( Aquila chrysaetos ) typically forage on mammals; however, habitat across much of their range is experiencing degradation through changes in land use, climate, and human encroachment. In 2015, we examined the prevalence of T. gallinae infection in Golden Eagle nestlings across western North America and conducted an intensive study on factors associated with T. gallinae infection and trichomonosis in southwestern Idaho. We found T. gallinae infection in 13% (12/96) of eagle nestlings across 10 western states and in 41% (13/32) of nestlings in southwestern Idaho. At the Idaho site, the probability of T. gallinae infection increased as the proportion of Rock Pigeons in nestling diet increased. Nestlings with diets that consisted of ≥10% Rock Pigeons had a very high probability of T. gallinae infection. We compared historical (1971–81) and recent (2014–15) diet data and incidence of trichomonosis lesions of nestling eagles in Idaho and found that the proportion of Rock Pigeons in eagle diets was higher in recent versus historical periods, as was the proportion of eagle nestlings with trichomonosis lesions. Our results suggested that localized shifts in eagle diet that result from habitat degradation and loss of historical prey resources have the potential to affect Golden Eagle nestling survival and supported the hypothesis that land use change can alter biologic communities in a way that might have consequences for disease infection and host susceptibility.

Journal of Wildlife Diseases↗