Estimating flight heights of seabirds using optical rangefinders and GPS data loggers: a methodological comparison

Borkenhagen, Kai; Corman, Anna‐Marie; Garthe, Stefan

doi:10.1007/s00227-017-3273-z

Cited by 21 publications

(21 citation statements)

References 19 publications

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“…Although Borkenhagen et al. () suggested that measuring altitudes of birds flying very low with a rangefinder was difficult, we did not experience any such bias and this may be due to differences between studies in equipment or survey platforms. Indeed, larger, more stable survey vessels may also reduce variability in rangefinder measurements, but could also influence surveyor and rangefinder performance given a greater eye height.…”

Section: Discussionmentioning

confidence: 66%

“…Borkenhagen et al. () used a more sophisticated (i.e., more expensive) rangefinder (< 2% of values to −3 m) and altimeters in GPS tags (0.3% of records to −10 m), but also reported negative heights, as did Cleasby et al. () using GPS tags (2.7% of flight records at ≤ 0 m).…”

Section: Discussionmentioning

confidence: 95%

“…), and from a boat platform to derive flight‐height distributions for 15 seabird taxa (Borkenhagen et al. ). Rangefinders have also been used as a form of theodolite (the “ornithodolite”) from a fixed station to track the three‐dimensional movements of birds and determine their air speed (Pennycuick et al.…”

mentioning

confidence: 99%

“…Estimates of the heights of flying birds are critical to understanding collision risks as part of impact assessments and determination of appropriate mitigation at wind farms (de Lucas et al 2012, Johnston et al 2014, Marques et al 2014, Masden and Cook 2016, Thaxter et al 2017. Flight heights of birds have been determined using a range of methods, including optical rangefinders (hereafter, rangefinders), digital aerial surveys, fixed-beam radar, thermal imagery, tag telemetry, and LiDAR (light detecting and ranging systems) as well as, most commonly, surveyors simply estimating heights both on land and during boat-based surveys at sea (Bruderer and Liechti 1995, Camphuysen et al 2004, Garvin et al 2011, Bouten et al 2013, Corman and Garthe 2014, Stantial and Cohen 2015, Thaxter et al 2015, Johnston and Cook 2016, Borkenhagen et al 2018, Skov et al 2018.…”

mentioning

confidence: 99%

“…The use of rangefinders in combination with visual observations is often advocated for onshore monitoring to provide height and distance estimates for collision risk assessments (Madders and Whitfield 2006, Stantial and Cohen 2015, Wulff et al 2016. Offshore, rangefinders have been employed from wind turbine platforms at-sea to track birds and determine flight heights (Skov et al 2018), and from a boat platform to derive flight-height distributions for 15 seabird taxa (Borkenhagen et al 2018). Rangefinders have also been used as a form of theodolite (the "ornithodolite") from a fixed station to track the three-dimensional movements of birds and determine their air speed (Pennycuick et al 2013).…”

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confidence: 99%

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Use of an optical rangefinder to assess the reliability of seabird flight heights from boat‐based surveyors: implications for collision risk at offshore wind farms

Harwood¹,

Perrow²,

Berridge³

2018

J. Field Ornithol.

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Visual estimates of the distribution of the flight heights of birds are often critical for collision risk assessments for wind‐energy projects. However, the reliability of such data is largely unknown. The results of trials where rangefinder height estimates were compared with those of an Unmanned Aerial Vehicle (UAV) used to mimic a flying bird at varying distances and heights from the operator suggested that the rangefinder performed well, with an overall mean deviation from the actual UAV height of −0.4 m. Accuracy and precision were influenced by an interaction between UAV height and distance to the surveyor. We also compared measurements of the flight heights of 16 species of seabirds made with an optical rangefinder to surveyor estimates made in 5‐m bands during boat‐based surveys off the east coast of Scotland UK from May to October 2017. Overall agreement between the rangefinder and surveyor estimates (N = 1235) was 58%, but increased to 92% when including the adjacent 5‐m bands. We found that surveyors were more likely to underestimate bird heights, potentially influencing collision‐risk assessments for wind farm projects. Use of rangefinders may be limited to days with good visibility, but their accuracy can be excellent within equipment limitations. However, suitability of rangefinders for the species or task in question should be verified before application. Further use of rangefinders is recommended for training, assessment of surveyor accuracy and consistency, calibration of visual flight height distributions, or replacement of visual observations where appropriate. Such applications could increase confidence in impact assessments and inform appropriate mitigation for wind farms.

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Section: Discussionmentioning

confidence: 66%

Section: Discussionmentioning

confidence: 95%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Use of an optical rangefinder to assess the reliability of seabird flight heights from boat‐based surveyors: implications for collision risk at offshore wind farms

Harwood¹,

Perrow²,

Berridge³

2018

J. Field Ornithol.

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Temporal patterns in offshore bird abundance during the breeding season at the Dutch North Sea coast

et al. 2021

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The expanding development of offshore wind farms brings a growing concern about the human impact on seabirds. To assess this impact a better understanding of offshore bird abundance is needed. The aim of this study was to investigate offshore bird abundance in the breeding season and model the effect of temporally predictable environmental variables. We used a bird radar, situated at the edge of a wind farm (52.427827° N, 4.185345° E), to record hourly aerial bird abundance at the North Sea near the Dutch coast between May 1st and July 15th in 2019 and 2020, of which 1879 h (51.5%) were analysed. The effect of sun azimuth, week in the breeding season, and astronomic tide was evaluated using generalized additive modelling. Sun azimuth and week in the breeding season had a modest and statistically significant (p < 0.001) effect on bird abundance, while astronomic tide did not. Hourly predicted abundance peaked after sunrise and before sunset, and abundance increased throughout the breeding season until the end of June, after which it decreased slightly. Though these effects were significant, a large portion of variance in hourly abundance remained unexplained. The high variability in bird abundance at scales ranging from hours up to weeks emphasizes the need for long-term and continuous data which radar technology can provide.

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Aerial photogrammetry of seabirds from digital aerial video images using relative change in size to estimate flight height

Humphries¹,

Fail²,

Watson³

et al. 2023

Mar Biol

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Estimating flight heights of seabirds using optical rangefinders and GPS data loggers: a methodological comparison

Cited by 21 publications

References 19 publications

Use of an optical rangefinder to assess the reliability of seabird flight heights from boat‐based surveyors: implications for collision risk at offshore wind farms

Use of an optical rangefinder to assess the reliability of seabird flight heights from boat‐based surveyors: implications for collision risk at offshore wind farms

Temporal patterns in offshore bird abundance during the breeding season at the Dutch North Sea coast

Aerial photogrammetry of seabirds from digital aerial video images using relative change in size to estimate flight height

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