Comparison of bird migration in a radar wind profiler and a dedicated bird radar

Authors: Nadja Weisshaupt, Maxime Hervo & Birgen Haest

Year: 2023

Publication: Remote Sensing in Ecology and Ecology

Publication Link:

Keywords: biological radar, bird migration, radar wind profiler, weather

Abstract: Various types of radar systems are increasingly being used to monitor aerial
biodiversity. Each of these types has different detection capabilities and sensitivities
to environmental conditions, which affect the quantity and quality of the
measured objects of interest. Radar wind profilers have long been known to
detect birds, but their use in ornithology has remained limited, largely because
of biologists’ unfamiliarity with these systems. Although the potential of radar
wind profilers for quantitative bird monitoring has been illustrated with time
series of raw data, a comparison with a similar radar system more established
in biology is missing. Here, we compare nocturnal bird migration patterns
observed by a radar wind profiler during October 2019 and April 2021 with
those from a dedicated bird radar BirdScan MR1. The systems were located
50 km apart with an altitudinal difference of about 850 m. The nightly migration
intensities measured with both systems were highly correlated in both
spring and autumn (Pearson correlation coefficient 0.8, P < 0.001), but estimated
traffic measured by the radar wind profiler was on average five times
higher in spring and nine times higher in autumn. Low ratios of the migration
traffic rates of the Birdscan MR1 to those of the radar wind profiler occurred
primarily in clear conditions. In both radar systems, migration occurred at significantly
higher altitudes in spring than in autumn. Discrepancies in absolute
numbers between both systems are likely due to both system-inherent and
external environmental and topographical factors, but also different quantification
approaches. These findings support the capacity of radar wind profilers for
aerial biomonitoring, independent of environmental conditions, and open up
further avenues for studying the impact of weather on bird migration at
detailed temporal and altitudinal scales.

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