Does the decline in numbers of Ringed Plovers breeding in a river catchment in the central Highlands of Scotland reflect the extent and suitability of habitats?

N.E. BUXTON

The number of pairs of breeding Ringed Plovers decreased on rivers in Badenoch in the central Highlands of Scotland during 1993–2017. Breeding birds were counted along a 42 km section of the River Spey, its associated tributaries and adjacent lochs. Potential influences on the population were assessed. By 2007 Ringed Plovers had ceased to breed on most shingle banks along the main stem of the River Spey, decreased on its tributaries and also at some nearby lochs in the catchment. Whilst the extent of available breeding habitat decreased and management of adjacent agricultural areas had changed, potential prey abundance on territories suggested no trend over seven years, and changes in river flow rates were subtle. A confounding factor was that wintering numbers in Scotland and the UK decreased along with the breeding numbers in the study area so further work is necessary to determine whether limiting factors are acting on the breeding or wintering grounds.

Introduction

The Ringed Plover Charadrius hiaticula breeds commonly in both coastal and inland habitats throughout many parts of the UK (Balmer et al. 2013), and has done so for many decades (Holloway 1996). Murray (1986) suggested that there had been a sequential new colonisation by breeding birds from the coast along the River Tweed in the last few years of the 18th century and, whilst many observers including Harvie-Brown & Buckley (1887), Booth et al. (1984), Smout (1986), and Vittery (1997) have noted pairs inland, few have commented on changes in numbers. The three BTO breeding bird atlases (Sharrock 1976, Gibbons et al. 1993, Balmer et al. 2013), presenting data approximately 40 years apart (1968–72, 1988–9 & 2007–11) and national population surveys (Conway et al. 2019), allowed both range and some numerical comparisons within the UK, but the only contemporary detailed study in the UK until the late 20th century was in north-west England (Briggs 1983). As a result, in comparison to coastal birds, little was known of the dynamics of inland populations. This was the case in the Badenoch area, where Ringed Plovers have bred for over 100 years (Harvie Brown & Buckley 1896, Nethersole-Thompson & Watson 1981, Dennis 1995). The aim of this study was to describe the distribution and any fluctuations in numbers of Ringed Plovers over 25 years (1993 to 2017) in Badenoch in relation to variations in the availability of breeding habitat and prey.

Methods Study area

The study area lay in Badenoch in the central Highlands of Scotland (Figures 1a & b) and comprised locations within a 42 km stretch of the River Spey, from Kingussie westwards to 12 km upstream of Spey Dam (the upper River Spey) and lengths of three of its tributaries (the Rivers Truim, Calder, and Dulnain) and the River Findhorn (Table 1), along all of which shingle banks occurred. All the shingle banks within the study area were initially surveyed for breeding Ringed Plovers and those supporting

Does the decline of Ringed Plovers breeding in the central Highlands reflect the extent and suitability of habitats? 43:3 (2023)