The decline of a population of farmland breeding waders: a twenty-five-year case study

Long-term studies can make an important contribution to our understanding of wader decline, as is demonstrated by work carried out by BTO’s Regional representative for Perthshire, Mike Bell. Mike had the foresight to start monitoring what was an important concentration of breeding waders in Strathallan (Perthshire, Scotland) in the late 1980s. Twenty-five years after establishing repeatable methods over the study area proved an appropriate time to take stock of changes that occurred. The four most numerous species in the area were Oystercatcher, Lapwing, Curlew and Redshank, which respectively achieved densities of 12, 36, 3 and 5 pairs per km² in 1990. All are facing serious declines across the UK. Alongside information on the breeding populations of these four waders, Mike also documented agricultural changes; from this it was possible to determine how local farming practices were likely to have influenced the waders.

Over the period of 1990-2015 Oystercatchers showed the greatest proportional decline with the breeding population falling by 95%, followed by Lapwing (-88%), Redshank (-87%) and Curlew (-67%). Although the greatest declines were associated with changing land use, the declines appeared greater than could be accounted by losses of preferred habitat alone. Furthermore, breeding success was low throughout the study and probably not sufficient to maintain the population. This raises the importance of understanding the roles of source and sink populations for breeding waders in the wider countryside. Alongside this, threats from poor weather, increased disturbance (e.g. from dog walkers), and increased predator numbers could further implicate the population, although this was not studied specifically at Strathallan.

Mike Bell is a long-term volunteer for the BTO and now Regional Representative for Perthshire. This 25-year (and ongoing) study was undertaken in his own time, highlighting the value of volunteers to science and conservation. It also emphasises how long-term datasets such as this can provide invaluable insights into the pressures that bird species are facing, and how we may alleviate these pressures. As most long-term studies are possible only with volunteers, the importance of their contribution is increasingly important. With support from the BTO’s recent Curlew Appeal, BTO has been trialling a range of approaches where volunteers can add to our understanding of the ecology of breeding waders, knowledge which will be vital to provide these beautiful birds with a fighting chance.