Abstract
Ground‐nesting species are vulnerable to a wide range of predators and often experience very high levels of nest predation. Strategies to reduce nest vulnerability can include concealing nests in vegetation and/or nesting in locations in which nests and eggs are camouflaged and less easy for predators to locate. These strategies could have important implications for the distribution of ground‐nesting species and the success rates of nests in areas with differing vegetation structure. However, the factors influencing the success of nest concealment and camouflage strategies in ground‐nesting species are complex. Here we explore the effects of local vegetation structure and extent of nest concealment on nest predation rates in a range of ground‐nesting, sympatric wader species with differing nest concealment strategies (open‐nest species: Oystercatcher Haematopus ostralegus, Golden Plover Pluvialis apricaria and Whimbrel Numenius phaeopus; concealed‐nest species: Black‐tailed Godwit Limosa limosa, Redshank Tringa totanus and Snipe Gallinago gallinago) in south Iceland, in landscapes that comprise substantial variability in vegetation structure at a range of scales. We monitored 469 nests of these six wader species in 2015 and 2016 and ~40% of these nests were predated. Nest predation rates were similar for open‐nest and concealed‐nest species and did not vary with vegetation structure in the surrounding landscape, but nest‐concealing species were ~10% more likely to have nests predated when they were poorly concealed, and the frequency of poorly concealed nests was higher in colder conditions at the start of the breeding season. For concealed‐nest species, the reduced capacity to hide nests in colder conditions is likely to reflect low rates of vegetation growth in such conditions. The ongoing trend for warmer springs at subarctic latitudes could result in more rapid vegetation growth, with consequent increases in the success rates of early nests of concealed‐nest species. Temperature‐related effects on nest concealment from predators could thus be an important mechanism through which climate change affecting vegetation could have population‐level impacts on breeding birds at higher latitudes.
Highlights
Among ground-nesting birds, nest camouflage and nest concealment are commonly observed and are likely to influence vulnerability to predation
These landscapes comprise large areas of semi-natural habitats interspersed with agricultural land. At these subarctic latitudes (63°–66°N) the growing season is very short, with both the onset of vegetation growth and the rate of growth being highly temperature-dependent (Thorvaldsson et al 2005, Alves et al 2019). These conditions provide an opportunity to explore how nest predation rates of ground-nesting birds vary in relation to vegetation height and structure, and how this varies among species that employ nest camouflage or nest concealment strategies
Nests were located at 10 SITES across south Iceland (Fig. 1), all of which comprised open habitats with vegetation structures ranging from bare ground to grassy areas, and in landscapes comprising a mix of semi-natural and agricultural habitats
Summary
Among ground-nesting birds, nest camouflage and nest concealment are commonly observed and are likely to influence vulnerability to predation. Wading bird species, adopt a strategy in which nests are laid on bare ground or small stones, against which adult plumage and/or egg coloration are camouflaged (Troscianko et al 2016) These species typically rely on early detection of predators by breeding in open landscapes (Amat & Masero 2004, Bulla et al 2016) and increased vegetation cover can delay their departure from nests when potential predators are detected (Gomez-Serrano & Lopez-Lopez 2014). These landscapes comprise large areas of semi-natural habitats interspersed with agricultural land (primarily for livestock grazing and hayfields; Johannesdottir et al 2018, 2019) At these subarctic latitudes (63°–66°N) the growing season is very short, with both the onset of vegetation growth and the rate of growth being highly temperature-dependent (Thorvaldsson et al 2005, Alves et al 2019). These conditions provide an opportunity to explore how nest predation rates of ground-nesting birds vary in relation to vegetation height and structure, and how this varies among species that employ nest camouflage or nest concealment strategies
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