Abstract
This report builds on the outcomes of D3.1, which covered a feasibility study of Laser Range Finder (LRF) work to ascertain seabird flight heights as well as a calibration study to ascertain the precision and accuracy of the two main LRFs we intended to use in Year 1 of the ProcBe project. The LRF work to collect flight height data on Manx Shearwaters (MSW) and storm petrels is intended to complement the work of Work Packages 1 and 2 that are collecting flight height data on these species using tagging devices on individuals from a range of sites.
A successful calibration trial (involving testing LRFs against objects of known height and a drone) at the start of the year allowed us to train fieldworkers and gave valuable information on the limitations of the two main devices. As a result of this trial, land-based fieldwork was determined to be practically achievable for the summer of 2024.
Fieldwork at two principal sites demonstrated that calibrating land-based heights, including observer height, was challenging at times due to difficulties in acquiring an accurate height above sea level at all times. However, we developed a new LRF methodology for calibrating bird flight heights above sea level collected on land, using objects on the sea surface at a range of distances.
We determined the limitations of both devices getting ‘real world’ data, compared with findings from the earlier calibration trial. The Nikon LRF appeared to be most effective out to 100m distance, with declining accuracy and precision beyond this distance. The Vector LRF appeared to be most effective out to 100m, but also collected reasonable data out to 100-300m distance. The calibration trial in March 2024 using the Vector pointed to a marginal but consistent under-estimate of flight height (<1.0m) under 300m, although this requires further testing. Overall, the Vector was found to be more accurate and precise than the Nikon.
We collected 79 records of MSW flight height in Phase 1 (May 2024) and 137 in Phase 2 (July/August 2024). While this is not sufficient data to calculate flight height distributions currently, the Year 1 data collection provides a proof of concept, demonstrates the feasibility of collecting reliable land-based data within defined distances, and allows us to make recommendations as to the feasibility and focus of future boat-based data collection. Opportunistic boat-based data collected in Year 1 indicated birds flew much closer to the observer during vessel-based surveys than land-based surveys. We anticipate that boat-based work in Year 2 will eliminate some of the problems encountered in Year 1 due to: 1) a new LRF model with increased range becoming available to the project, 2) birds being closer to the observer (and therefore LRF) than earlier land-based restricted observations, and 3) reduced need to calibrate with objects on the sea surface, due to known height above sea level.