Analysis Of Low Level Nocturnal Bird Migration

Author : Marc Victor d'Entremont
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (133 download)

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Download or read book Movement Patterns of Noctural Avian Migrants at a Wind Energy Project in Northeast British Columbia written by Marc Victor d'Entremont and published by . This book was released on 2015 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: "In North America, the migration corridors of passerine birds between breeding and non-breeding grounds are relatively well documented, and along these corridors passerines generally move in a broad-front fashion interspersed with stopover periods in which to rest and replenish fuel stores. Understanding movement patterns at individual locations along these routes is required to identify whether anthropogenic developments, such as wind energy installations, can lead to disruption or collision risk during migrations. Wind energy installations are becoming more numerous in the corridors along migration routes as they use the same wind resources exploited by migratory birds. Documenting collision risk to nocturnal migrants, particularly passerines, through the collection of accurate data on the movement patterns and flight altitudes at wind energy sites during both pre-operational and operational phases is needed to correctly assess the level of risk to these birds. Using standard marine radar units equipped with an inexpensive digital interface system, I automated the detection and extraction of radar echo signatures or target information for nocturnal migrants (Chapter 2) at a wind energy site in northeast British Columbia. Using the open source software program radR, I identified optimal values for input criteria to automatically detect and track these migrants with high accuracy from the digital radar data, when compared to known, manually-tracked targets (R2=0.94). The program was also effective in reducing the amount of insects that were detected and tracked. Use of the auto-tracking software also increased the number of detected targets by over 500% compared to the real-time collection of radar data. Using radR, I analyzed the micro-scale movements of nocturnal migrants during the pre-operational and operational periods of the wind energy project (Chapter 3). Despite variations in wind conditions between seasons, migrants showed consistent directionality and general trends of broad-front migration at altitudes typically above the height of wind turbines. In the spring, migrants were predominantly utilizing favourable tailwinds, but when wind conditions changed, migratory direction at the micro-scale level appeared to remain constant. In the fall, migrants were rarely moving with favourable winds and were predominantly facing headwind or crosswind conditions. Regardless, at the micro-scale level nocturnal migrants were not significantly adjusting their movements around the wind energy facility during the operational period and their typical migratory behaviour was not placing them in potential collision risk situations. Unfavourable weather and the influence of artificial lights have been identified as contributing factors in bird collisions with tall human-made structures. I used vertical radar data on the heights of migrating passerines to document the number of birds within 300 m height categories above ground per hour before and after 54 separate rain events. The number of birds did not increase in the lower height categories immediately before the rain event, suggesting that isolated rain events may not increase collision risk (Chapter 4). Nocturnal migrants rely on rod-dominated vision at night and are likely sensitive to intense artificial light sources. I broadcasted lights at different wavelengths (blue, green, red and white) and flash rates (solid or flashing) from a portable spotlight and documented the response of migrants (trajectories and heights of migrants) as they travelled past the light source (Chapter 5). Migrants exposed to light colours at shorter wavelengths consistently displayed lower flight altitudes compared to migrants exposed to light colours at longer wavelength. My results strongly suggest that artificial light colours at shorter wavelengths may have a greater attraction effect on nocturnal migrants than other lighting regimes. Overall, my results demonstrate that nocturnal migrants moving through northeast British Columbia are at a low risk of colliding with wind turbines under both favourable and unfavourable conditions."--Leaves i-iii.