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348 results on '"CLARK, NIGEL A."'

15. Effects of Horseshoe Crab Harvest in Delaware Bay on Red Knots: Are Harvest Restrictions Working?

Author

Niles, Lawrence J., Bart, Jonathan, Sitters, Humphrey P., Dey, Amanda D., Clark, Kathleen E., Atkinson, Phillip W., Baker, Allan J., Bennett, Karen A., Kalasz, Kevin S., Clark, Nigel A., Clark, Jacquie, Gillings, Simon, Gates, Albert S., González, Patricia M., Hernandez, Daniel E., Minton, Clive D. T., Morrison, R. I. Guy, Porter, Ronald R., Ross, R. Ken, and Veitch, C. Richard

Published
2009
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20. Chapter A Framework for Realistic Virtual Representation for Immersive Training Environments.

Author

Plumb, Caolan, Thomas, Hannah, Clark, Nigel, Pour Rahimian, Farzad, and Pandit, Diptangshu

Subjects
Digital twin, 3D reconstruction, Virtual reality, Laser scanning, Photogrammetry, Training simulation, Unreal Engine, thema EDItEUR::U Computing and Information Technology::UT Computer networking and communications::UTV Virtualization
Abstract

As mixed-reality (XR) technology becomes more available, virtually simulated training scenarios have shown great potential in enhancing training effectiveness. Realistic virtual representation plays a crucial role in creating immersive experiences that closely mimic real-world scenarios. With reference to previous methodological developments in the creation of information-rich digital reconstructions, this paper proposes a framework encompassing key components of the 3D scanning pipeline. While 3D scanning techniques have advanced significantly, several challenges persist in the field. These challenges include data acquisition, noise reduction, mesh and texture optimisation, and separation of components for independent interaction. These complexities necessitate the search for an optimised framework that addresses these challenges and provides practical solutions for creating realistic virtual representations in immersive training environments. The following exploration acknowledges and addresses challenges presented by the photogrammetry and laser-scanning pipeline, seeking to prepare scanned assets for real-time virtual simulation in a games-engine. This methodology employs both a camera and handheld laser-scanner for accurate data acquisition. Reality Capture is used to combine the geometric data and surface detail of the equipment. To clean the scanned asset, Blender is used for mesh retopology and reprojection of scanned textures, and attention given to correct lighting details and normal mapping, thus preparing the equipment to be interacted with by Virtual Reality (VR) users within Unreal Engine. By combining these elements, the proposed framework enables realistic representation of industrial equipment for the creation of training scenarios that closely resemble real-world contexts

Published
2023
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31. Evaluating the Impact of Headstarting on the Critically Endangered Spoon-Billed Sandpiper Calidris pygmaea.

Author

Loktionov, Egor Y., Digby, Roland A., Yakushev, Nickolay N., Shepelev, Ivan A., Clements, Jodie P., Tomkovich, Pavel S., Jarrett, Nigel S., Clark, Nigel A., Green, Rhys E., Lappo, Elena G., and Syroechkovskiy, Evgeny E.

Subjects
SANDPIPERS, COMMUNITIES, SEX ratio, PHILOPATRY, EGGS, CHICKS
Abstract

Headstarting is a conservation approach that suggests offering an advantage to a population by improving egg production, survival of embryos and/or juveniles. In this article, we are providing the quantitative data obtained during 10 years for different stages of headstarting (production of eggs per pair, hatching and fledging rates) and the resulting impact (survival to maturity, philopatry rate, sex ratio, apparent survival, growth/decline rate) on the local population of the critically endangered spoon-billed sandpiper. We have shown that headstarting gains are reduced over time from fledging to long-term recruitment to the local breeding population. The possible reasons for this reduction are suggested and discussed. The unexpected finding was a drastic difference in sex ratios of the new recruits, which was about even for headstarting, but strongly male-biased for wild-reared birds. We suggest this happens due to increased mortality of female chicks in nature. We have also shown only headstarting could stop the global decline of the species, particularly once the suggested improvements are implemented and the number of pairs involved is scaled up. Headstarting also had a significant social effect due to the involvement of increasing numbers of people both in the local communities in Chukotka and from many countries on the flyway into searching for marked birds and learning about waders, raising awareness about ecological problems on the East Asian–Australasian Flyway. Thus, it has made the need for conservation actions on the flyway more obvious and sensible. [ABSTRACT FROM AUTHOR]

Published
2023
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33. Daily, seasonal, and annual variation in area use of Lesser Black-backed Gulls Larus fuscus related to offshore renewable developments.

Author

Clewley, Gary D., Thaxter, Chris B., Scragg, Emily S., Masden, Elizabeth A., Barber, Lee J., Conway, Greg J., Clark, Nigel A., and Burton, Niall H.K.

Abstract

Individually tracked Lesser Black-backed Gulls Larus fuscus rarely visited offshore areas in this study but showed high variation across multiple time scales in overall area use. To quantify the variation in space use by Lesser Black-backed Gulls, a species of conservation concern, from short- and long-term data on tracked individuals, and to assess the time spent offshore and interacting with offshore wind farms (OWFs) before and after their construction. GPS tracking data were collected between 2016 and 2019 from 36 Lesser Black-backed Gulls breeding in a declining colony in the UK with several operational OWFs nearby. Variations in home ranges, foraging trip metrics and the proportion of time spent offshore or within OWFs were analysed at three temporal scales: (i) over a daily cycle, (ii) across the breeding season and (iii) between years. Individuals predominantly used terrestrial areas. Less than 1.25% of the overall breeding season time budgets were spent offshore across years, and offshore use and time within OWFs did not vary significantly between years. However, home range sizes and foraging trip metrics did vary significantly across all time scales and individual variation was significant. Our results suggested that there was little change in the relative use of offshore areas over time and thus in the macro-scale response of Lesser Black-backed Gulls to the OWFs, one of which was under construction during the period of study. Colony productivity and changes in the terrestrial environment were likely to be more important for influencing foraging movements at this colony. [ABSTRACT FROM AUTHOR]

Published
2023
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34. Estimating recruitment rate and population dynamics at a migratory stopover site using an integrated population model.

Author

Tucker, Anna M., McGowan, Conor P., Nuse, Bryan L., Lyons, James E., Moore, Clinton T., Smith, David R., Sweka, John A., Anstead, Kristen A., DeRose‐Wilson, Audrey, and Clark, Nigel A.

Subjects
LIMULUS polyphemus, LIMULIDAE, SHORE birds, ACQUISITION of data, GROWTH rate, SURVIVAL analysis (Biometry)
Abstract

Consideration of the full annual cycle population dynamics can provide useful insight for conservation efforts, but collecting data needed to estimate demographic parameters is often logistically difficult. For species that breed in remote areas, monitoring is often conducted during migratory stopover or at nonbreeding sites, and the recruitment rate of new breeding adults can be difficult to estimate directly. Here, we present an integrated population model that uses mark‐resight and count data to estimate survival probability, population growth rate, and recruitment rate for an Arctic‐breeding shorebird of conservation concern, the red knot (Calidris canutus rufa), from data collected during spring stopover in Delaware Bay, USA, from 2005 to 2018. At this site, red knots feed primarily on the eggs of spawning horseshoe crabs (Limulus polyphemus), a legally harvested species. We used this model to estimate the relationship between horseshoe crab abundance and red knot demographics, which informed a recent revision to the framework used to establish horseshoe crab harvest regulations. Our analysis indicates that the red knot population was most likely stable from 2005 to 2018 (average λ = 1.03, 95% credible interval [CRI]: 0.961, 1.15) despite low recruitment rates (average ρ = 0.088, 95% CRI: 0.012, 0.18). Adult survival probability was positively associated with horseshoe crab abundance in the same year (β = 0.35, 95% CRI: 0.09, 0.63), but we found no effect of horseshoe crab abundance two years previously on recruitment of new adults (β = −0.08, 95% CRI: −0.41, 0.38). Our approach demonstrates the utility of integrated population models for understanding population dynamics, even when data are only available from migratory stopover monitoring. [ABSTRACT FROM AUTHOR]

Published
2023
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