25 research outputs found
FLIGHT PATHS AND CHANGING PATTERNS: TRACKING INDIVIDUAL BIRDS TO UNDERSTAND AERIAL HABITAT SELECTION AND MIGRATION STRATEGIES
No full textAerial migrants such as birds must contend with dynamic atmospheric conditions that have the capacity to greatly assist or impede their movements. Understanding habitat selection aloft provides powerful insights into how birds complete their biannual journeys, both about how conditions shape behaviors and how birds may respond to future conditions. The earliest studies of flight behavior were estimated by using weather radar, with radar studies continuing to provide observations of the system-wide migration patterns. However, species and individual level data of flight behavior (i.e. altitudinal profiles of a species, departure and arrival behaviors) and migration strategies is logistically challenging to collect but would facilitate empirical hypothesis testing about aerial habitat selection and flight strategies. Fortunately, the recent production of more affordable and lightweight multi-sensor data-logging devices that can collect high resolution spatiotemporal data is helping to bridge the gap between data collection and research questions regarding aerial habitat. My dissertation uses data collected on individuals by the most recent tracking technology to address gaps in knowledge about the relationships between animal movement and environmental conditions in the air. In Chapter 1, we reanalyze historical movement data collected by light-level geolocators, a type of tag that estimates location by the timing of sunrise and sunset, to ask questions about how life history traits and atmospheric conditions affect decisions to depart rest and refueling areas during migration. Because birds are expected to be limited in time and energy during migration, departure from rest and refueling areas, or stopover areas as they are more commonly known, has received much study, but with inconclusive evidence of driving atmospheric factors as well as life history traits. We find that large temperature changes, average migration distance, windspeed, and interaction of body size and surface pressure had positive effects on departure, that is the individual was more likely to depart under those conditions, and that if it was fall migration, the time since arrival to departure, the interaction of the time since arrival and temperature at departure had negative relationships with departure. In Chapter 2, I use high resolution GPS tracking data from Long-billed Curlews (Numenius americana) to compare how current migration strategies, including departure time, migration duration, and migration speed may have changed in the last decade. Though migration distances haven’t changed, we find that southbound departure was delayed for both sexes, but an overall faster migration pace has led to an earlier arrival to the wintering grounds especially for males. While male departure dates in spring show little change, female departures were delayed. Spring arrival time to the breeding grounds, however, appears unchanged for both sexes. We also described flight bouts and found that Long-billed Curlews completed their ~2500 km migration usually in several bouts. In both seasons, the first bout was generally the longest, however southbound first bouts often covered 50% of the total flight distance compared to in northbound migration where the first bout covered only 25% of the total flight distance. Faster groundspeeds were significant for longer distances covered in a flight bout. In Chapter 3, I investigate flight speeds and aerial habitat selection of Long-billed Curlews during migration using high resolution GPS tracking data. We found strong differences between diel and seasonal cycles for flight speeds and altitudes and that temperature, wind support, and boundary layer height had the strongest effects on altitude selection. For example, while Long-billed Curlews often reach heights above 5000 meters above sea level during prolonged flights that extended into daylight hours, these prolonged diurnal flights only happened in the fall season
EXPERIENCE, NEIGHBHORHOODS, AND HABITATS: BREEDING DISPERSAL OF MALE BLACK-CAPPED VIREOS (VIREO ATRICAPILLA)
No full text1. Mechanisms driving breeding dispersal are complex and potentially interactive. These mechanisms are of general interest because dispersal strongly links individual fitness to population dynamics. We examine the relative importance of personal information, neighborhood effects, and structural habitat characteristics in determining an individual’s propensity for breeding dispersal.
2. To document dispersal events in 2017 and 2018, we individually marked and radio tagged male black-capped vireos in Southwestern Oklahoma. We used a classification tree analysis to explore ten potential factors that individuals used as information to evaluate for emigration. We used the correlation between arrival date and habitat structure to determine habitat preference.
3. Older and younger age classes that reproduced successfully did not disperse, but younger age class individuals that failed to reproduce were more likely to disperse than older individuals. Dispersal events among young males were significantly related to the proportion of their neighbors that successfully reproduced. More individuals dispersed from neighborhoods of fewer, less successful neighbors. Male black-capped vireos did not disperse due to the vegetation structure of their habitat, though there was a trend for young males to be located in habitats with structure less preferred by older males.
4. Breeding dispersal propensity among black-capped vireos, like many other avian species, depended mostly on their personal breeding experience, but also on reproductive information gleaned from their neighbors. In this Oklahoma population, black-capped vireos of different ages were spatially segregated into habitats of differing structure, which may further influence neighborhood quality and the degree to which age group participates in breeding dispersal.
5. Our results indicate localized, neighborhood effects are important to breeding dispersal, which has implications for the genesis of new populations or a population to become stabilized within a metapopulation. The creation of preferred habitat will be needed to produce rates of nest success that support healthy metapopulation dynamics. These preferred habitats are needed to balance potential high rates of breeding dispersal out of habitats with low neighborhood quality for this species. Future studies focused on the spatio-temporal aspects of breeding dispersal would be valuable. Especially useful would be studies of search behaviors of dispersing individuals and processes involved in selecting new habitat after leaving their initial territory. In general, further study is needed on interactions of multiple dispersal cues and how spatial structuring influences the evaluation of these cues by potential dispersers
Using Animal Movement Data to Uncover Hidden Links Between Long-Billed Curlews and Black-Tailed Prairie Dogs
No full textBlack-tailed prairie-dogs (PDs) are keystone species and ecosystem engineers in grassland systems of western North America. However, they have been eradicated from greater than 90% of their range through grassland conversion, persecution by humans, and introduced sylvatic plague. Because of how quickly and thoroughly prairie-dogs were lost from our grassland ecosystems, their role as a keystone species remains poorly understood. Based on field observations of large aggregations of breeding long-billed curlews (LBCU) in the vicinity of PD colonies, we hypothesized that curlews were using prairie-dog colonies for breeding and foraging disproportionately compared with their availability on the landscape. To test this, we tagged 32 LBCU over 4 years with GPS satellite tags and modeled resource selection on the breeding grounds in a study area containing several large PD colonies. Using continuous-time resource selection functions we found curlews do, in fact, select for active PD colonies. Confirmation of this pattern sets up several hypotheses for the mechanism underpinning this association, which out research group is currently testing. Finally, this PD-LBCU link is an example of a potentially important keystone function of PDs in grassland systems, one that we stand to lose in the absence of large-scale PD conservation efforts
Author response
No full textThe hormone estrogen (E2) binds the estrogen receptor to promote transcription of E2-responsive genes in the breast and other tissues. E2 also has links to genomic instability, and elevated E2 levels are tied to breast cancer. Here, we show that E2 stimulation causes a rapid, global increase in the formation of R-loops, co-transcriptional RNA-DNA products, which in some instances have been linked to DNA damage. We show that E2-dependent R-loop formation and breast cancer rearrangements are highly enriched at E2-responsive genomic loci and that E2 induces DNA replication-dependent double-strand breaks (DSBs). Strikingly, many DSBs that accumulate in response to E2 are R-loop dependent. Thus, R-loops resulting from the E2 transcriptional response are a significant source of DNA damage. This work reveals a novel mechanism by which E2 stimulation leads to genomic instability and highlights how transcriptional programs play an important role in shaping the genomic landscape of DNA damage susceptibility
Delineating ecologically distinct groups for annual cycle management of a declining shorebird
No full text1. Patterns of migratory connectivity are increasingly used to understand and manage threats throughout the annual cycle of migratory species. Strong migratory connectivity refers to when individuals from different populations remain spatially separated across the annual cycle, which may expose populations to unique sets of threats and conditions that cause differential population trends. However, the populations or groups used for species' management are often defined a priori based on expert knowledge and/or management units, which may mask important population segregation and obscure differential population trends and their drivers.
2. We compared three approaches to defining management groups of a declining shorebird, the long-billed curlew (Numenius americanus), for annual cycle management: by expert-opinion, according to management flyways, and with unsupervised clustering of satellite tracking data that maximizes the strength of migratory connectivity.
3. Despite the curlews having a continuous breeding range and a pattern of parallel migration, all three approaches identified groups with different population trends, movement behaviours and habitat selection across the annual cycle, suggesting these are meaningful ecological groups. The expert and clustering approaches resulted in similar group structure, strong estimates of migratory connectivity (measured as MC = 0.64 across seasons), movement behaviour and habitat selection; however, the expert approach identified an additional divide between the easternmost grouping, which revealed strongly negative population trends in the group occupying the Chihuahuan desert during the stationary nonbreeding season. In contrast, the flyway delineation resulted in weaker estimates of migratory con- nectivity, marginal differences in population trends and less
between-group differences in movement behaviour and habitat selection.
4. Synthesis and applications. Using measurements of migratory connectivity in concert with expert opinion can define ecologically distinct groups for wildlife management that differ in the environmental conditions they experience across seasons of the annual cycle, which is a key component for understanding and reversing declines of migratory species.This article is published as Knight, Elly C., Jay Carlisle, Andy J. Boyce, David Bradley, Paula Cimprich, Stephanie Coates, Stephen J. Dinsmore et al. "Delineating ecologically distinct groups for annual cycle management of a declining shorebird." Journal of Applied Ecology (2025). doi:10.1111/1365-2664.14885.U.S. Bureau of Land Management; BC Hydro; John and Adrienne Mars; American Prairie; California Department of Fish and Wildlife; Meg and Bert Raynes Wildlife Fund; Habitat Conservation Trust Foundation; Columbia Basin Trust; McDanel Land Foundation; Page Family Foundation; Wyoming Governor's Office Big Game License Coalition; ConocoPhillips; Environment and Climate Change Canada; Nature Conservancy; MPG Ranch; U.S. Fish and Wildlife Service; Wyoming Game and Fish Departmen
The role of industrial actors in the circular economy for critical raw materials: a framework with case studies across a range of industries
No full textIn this article, we explore concrete examples of circularity strategies for critical raw materials (CRMs) in commercial settings. We propose a company-level framework for systematically evaluating circularity strategies (e.g., material recycling, product reuse, and product or component lifetime extension) in specific applications of CRMs from the perspectives of specific industrial actors. This framework is applied in qualitative analyses—informed by relevant literature and expert consultation—of five case studies across a range of industries: (1) rhenium in high-pressure turbine components, (2) platinum group metals in industrial catalysts for chemical processing and oil refining, (3) rare earth permanent magnets in computer hard disk drives, (4) various CRMs in consumer electronics, and (5) helium in magnetic resonance imaging (MRI) machines. Drawing from these case studies, three broader observations can be made about company circularity strategies for CRMs. Firstly, there are multiple, partly competing motivations that influence the adoption of circularity strategies, including cost savings, supply security, and external stakeholder pressure. Secondly, business models and value-chain structure play a major role in the implementation of circularity strategies; business-to-business models appear to be more conducive to circularity than business-to-consumer models. Finally, it is important to distinguish between closed-loop circularity, in which material flows are contained within the “focal” actor’s system boundary, and open-loop circularity, in which material flows cross the system boundary, as the latter has limited potential for mitigating material criticality from the perspective of the focal actor.Climate Design and Sustainabilit
