Perspectives in using shorebird counts for assessing long-term changes in wader numbers in the Wadden Sea

Abstract

Over the past 20 years, a tradition has developed in western Europe of carrying out shorebird surveys in estuaries. These counts are mostly conducted by amateur ornithologists, usually well acquainted with the area in which they are active. The results of these surveys are well reproducible for at least the abundant species, and information is available on the size of the errors which occur. In several parts of Europe, shorebird surveys have been carried out long enough to allow trend analysis of population size. Four examples from Great Britain demonstrate that monitoring schemes may also be used for management purposes, especially if combined with specific research projects. Long-term shorebird surveys can be used not only for simple analysis of trends in bird numbers, but also to provide a deeper understanding of the functioning of the ecosystem. They may also act as a tool to document the .effects of management activities in the area concerned. Shorebird surveys in the Wadden Sea have not only revealed the extremely large importance of the area, especially for waders, but also show that different areas are exploited in different ways. They have also provided data on changes in bird numbers throughout the year.

Frequency‐dependent tolerance to aircraft disturbance drastically alters predicted impact on shorebirds

“…At the same time, aircraft disturbance is difficult to study since performing experiments is hardly feasible (but see Ward et al, 1999), and most studies rely on observations at sites where aircraft overflights are common (Blackwell et al, 2019;van der Kolk, Krijgsveld, et al, 2020). Many studies highlighted large differences in disturbance potential among aircraft types (Blackwell et al, 2019;Goudie, 2006;Komenda-Zehnder & Bruderer, 2002;Smit & Visser, 1993;van der Kolk, Krijgsveld, et al, 2020), but sometimes with contrasting rankings. For example, Komenda-Zehnder and Bruderer (2002) concluded that transport aircraft were less disturbing than jets, helicopters and small civil airplanes, whereas van der Kolk, Krijgsveld, et al (2020) showed that transport aircraft had by far the highest disturbance potential among these same types of aircraft.…”

Aerial Surveys Do Not Reliably Survey Boreal-nesting Shorebirds

“…Specifically, the concordance between aerial observations and the actual number of breeding birds (i.e., the detection rate) has not been established for boreal-nesting shorebirds, or for most small birds. With no objective measurement of bias, the reliability of aerial surveys for shorebirds is unknown (Smit 1989). In this study, we attempted to measure detection rates for aerial surveys of three species of boreal-nesting shorebirds, and examined what parameters affected detection.…”