Comparison of visual bird migration counts with radar estimates |
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Authors: | Matthias Schmidt Janine Aschwanden Felix Liechti Gábor Wichmann Erwin Nemeth |
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Affiliation: | 1. BirdLife ?sterreich, Vienna, Austria;2. Swiss Ornithological Institute, Sempach, Switzerland |
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Abstract: | In the context of an extensive study on bird migration in the Austrian Alps, we compared data from a fixed‐beam radar with data collected by visual observation to estimate the intensity of migrating birds up to a height of 150 m above the ground. Migration traffic rates calculated from visual bird counts and radar measurements were strongly correlated. Using resampling techniques, we calculated a minimum observation effort for counting birds during a 5‐week period of peak migration. We chose ±20% of the real mean as the criterion for a reliable estimation. Our results showed that at least 19 observation days are necessary to assess the mean number of migrants passing within this low altitudinal range. |
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Keywords: | Alps Austria environmental impact assessment observation effort wind farms |
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