A1 Refereed original research article in a scientific journal
How many observation days are needed to reliably describe bird migration? Hur många observationsdagar behövs för att tillförlitligt beskriva fågelflyttning?
Authors: Antti Tanskanen, Rauno A. Yrjölä, Ulrike Baum, Sakari Tanskanen, Jörgen Eriksson
Publisher: Sveriges ornitologiska förening
Publication year: 2018
Journal: Ornis Svecica
Journal name in source: Ornis Svecica
Volume: 28
Issue: 1
First page : 3
Last page: 13
ISSN: 1102-6812
eISSN: 2003-2633
DOI: https://doi.org/10.34080/os.v28.19519
Web address : https://journals.lub.lu.se/os/article/view/19519
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/41778771
The total number of migrating birds is needed, for example, to estimate collisions risk as part of the assessment process for wind-power parks. This estimation is often based on a small sample of observation days, making estimates uncertain. To determine the number of days needed to obtain reliable figures we used observations of migrating birds obtained from the Signilskär bird observatory, Åland, Finland during the autumn seasons from 2009 to 2013. We sampled 1–14 days during each 14 day time window and used linear extrapolation and Poisson regression with weather covariates to estimate the total number of migrating birds and distribution of estimates. We calculated the head-wind and side-wind components according to the species’ most common flight directions. We found that observations should cover at least 90% of the migration period to obtain precise results and 70–90% to obtain results sufficiently reliable to use in practice. Linear extrapolation is the best model for small samples. The larger the proportion of days observed, the better is Poisson regression with weather covariates.
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