Continental-scale radar monitoring of the aerial movements of animals

Summary Radars of various types have been used in ornithological research for about 70 years. However, the potential of radar wind profiler (RWP) as a tool for biological purposes remains poorly understood. The aim of this study is to assess the suitability of RWP for ornithological research questions. A 1290 MHz RWP at the south‐eastern coast of the Bay of Biscay has been known to exhibit seasonally occurring nocturnal signals attributed to migrating birds. As a first step to verify the origin of these seasonal patterns, historical radar data from 2010 to 2012 were analysed, and both bird patterns and temporal occurrence were identified in RWP data at different levels of the signal processing. A thermal‐imaging (TI) camera in conjunction with moon watching was used as verification systems at the radar site to confirm the ornithological origin of the radar echoes. The simultaneous data on spring migration served as a basis for the identification of biological signatures (qualitative parameters) on time‐series level (raw data) and to derive quantitative migration parameters (flight altitude, migration traffic rates) thereof. Finally, the quantitative measurements of the TI camera and the radar were compared considering meteorological conditions. The approach allowed identifying reproducible criteria based on time series to calculate migration traffic rates and altitudinal flight distribution. General flight directions were only available in the final wind data. In clear weather conditions, the calibration methods coincided well with the wind profiler data. Findings show that wind profiler raw data offer reliable information on migration intensity, flight altitudes and flight directions in a variety of meteorological conditions. The method presented can be applied as a complement to present efforts to use weather radars for large‐scale bird monitoring. Furthermore, it is also interesting for the meteorological community to refine signal‐processing methods.

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“…at higher altitudes or in the dark), as well as better applicability for large‐scale monitoring (Shamoun‐Baranes et al . ).…”

Section: Introductionmentioning

confidence: 97%

Radar wind profilers and avian migration: a qualitative and quantitative assessment verified by thermal imaging and moon watching

Weisshaupt¹,

Lehmann

Arizaga³

et al. 2017

Methods Ecol Evol

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“…; Shamoun‐Baranes et al . ). Radar has also been applied to ecological problems at more local scales, such as counting cryptic species (Burger ), avoiding bird–airplane collisions at airports (Nohara et al .…”

Section: Introductionmentioning

confidence: 99%

Quantitative ornithology with a commercial marine radar: standard‐target calibration, target detection and tracking, and measurement of echoes from individuals and flocks

Urmy

Warren

2016

Methods Ecol Evol

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Summary Marine surveillance radars are commonly used for radar ornithology, but they are rarely calibrated. This prevents them from measuring the radar cross‐sections (RCS) of the birds under study. Furthermore, if the birds are aggregated too closely for the radar to resolve them individually, the bulk volume reflectivity cannot be translated into a numerical density. We calibrated a commercial off‐the‐shelf marine radar, using a standard spherical target of known RCS. Once calibrated, the radar was used to measure the RCS of common and roseate terns (Sterna hirundo L. and Sterna dougallii Montagu) tracked from a land‐based installation at their breeding colony on Great Gull Island, NY, USA. We also integrated echoes from flocks of terns, comparing these total flock cross‐sections with visual counts from photos taken at the same time as the radar measurements. The radar's calibration parameters were determined with 1% error. RCS measurements made after calibration were expected to be accurate within ±2 dB. Mean tern RCS was estimated at −28 dB relative to one square meter (dBsm), agreeing in magnitude with a simple theoretical model. RCS was 3–4 dB higher when birds’ aspect angles were broadside to the radar beam compared with head‐ or tail‐on. Integrated flock cross‐section was linearly related to the number of birds. The slope of this line, an independent estimate of RCS, was −32 dBsm, within an order of magnitude of the estimate from individual birds, and near the middle of the frequency distribution of RCS values. These results indicate that a calibrated marine radar can count the birds in an aggregation via echo integration. Field calibration of marine radars is practical, enables useful measurements, and should be done more often.

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“…It has been used to estimate distances to birds (Petersen et al 2006), and in the context of a distance sampling survey to calibrate observer estimates of distanceto-bird measurements (Mateos et al 2010). Shamoun-Baranes et al (2014) propose the use of these systems to evaluate bird migrations at a continental scale.…”

Section: Radar Surveysmentioning

confidence: 99%