Abstract
Conservation grazing for breeding birds needs to balance the positive effects on vegetation structure and negative effects of nest trampling. In the UK, populations of Common redshank Tringa totanus breeding on saltmarshes declined by >50% between 1985 and 2011. These declines have been linked to changes in grazing management. The highest breeding densities of redshank on saltmarshes are found in lightly grazed areas. Conservation initiatives have encouraged low‐intensity grazing at <1 cattle/ha, but even these levels of grazing can result in high levels of nest trampling. If livestock distribution is not spatially or temporally homogenous but concentrated where and when redshank breed, rates of nest trampling may be much higher than expected based on livestock density alone. By GPS tracking cattle on saltmarshes and monitoring trampling of dummy nests, this study quantified (i) the spatial and temporal distribution of cattle in relation to the distribution of redshank nesting habitats and (ii) trampling rates of dummy nests. The distribution of livestock was highly variable depending on both time in the season and the saltmarsh under study, with cattle using between 3% and 42% of the saltmarsh extent and spending most their time on higher elevation habitat within 500 m of the sea wall, but moving further onto the saltmarsh as the season progressed. Breeding redshank also nest on these higher elevation zones, and this breeding coincides with the early period of grazing. Probability of nest trampling was correlated to livestock density and was up to six times higher in the areas where redshank breed. This overlap in both space and time of the habitat use of cattle and redshank means that the trampling probability of a nest can be much higher than would be expected based on standard measures of cattle density. Synthesis and applications: Because saltmarsh grazing is required to maintain a favorable vegetation structure for redshank breeding, grazing management should aim to keep livestock away from redshank nesting habitat between mid‐April and mid‐July when nests are active, through delaying the onset of grazing or introducing a rotational grazing system.
Highlights
Grazing by wild or domestic animals is commonly used to conserve landscapes and ecosystems and to preserve their associated species and communities (WallisDeVries, 1998)
As redshank nest in these higher elevation habitats, and breeding coincides with the early period of grazing (Adam, 1990; Hale, 1980), this pattern of grazing causes a much higher nest loss to trampling than would be expected merely based on the mean density of cattle on the saltmarsh, and means that some parts of the saltmarshes are grazed much more heavily than may be intended while large areas go completely ungrazed
Livestock grazing is used as a management tool for conserving numerous target species and communities in a wide range of landscapes and ecosystems (WallisDeVries, 1998), including heathlands, grasslands, and woodlands (Bakker, De Bie, Dallinga, Tjaden, & De Vries, 1983; Eglington et al, 2009; Smart, Gill, Sutherland, & Watkinson, 2006)
Summary
Grazing by wild or domestic animals is commonly used to conserve landscapes and ecosystems and to preserve their associated species and communities (WallisDeVries, 1998). Previous studies on the spatial distribution of livestock have found that their distribution can vary markedly in space and depends on numerous biotic and abiotic factors such as the availability of shelter, distance to drinking water, and forage quality and quantity (Bailey, 1995; Putfarken, Dengler, Lehmann, & Härdtle, 2008) These studies have focused mainly on intensively grazed highly managed pasture systems that tend to have a homogenous and species-poor vegetation with universal accessibility. European saltmarshes are an important breeding habitat for a range of ground nesting bird species, for example, common redshank (Tringa totanus: hereafter redshank; Figure 1), eurasian oystercatcher (Haematopus ostralegus), eurasian skylark (Alauda arvensis), and meadow pipit (Anthus pratensis) These species tend to nest in the higher elevation saltmarsh zones that are closer to the landward edge and out of reach of most high tides (van Klink et al, 2016; Norris, Cook, Odowd, & Durdin, 1997). When water and food are spatially separated, cattle can spend up to 45% of their time grazing and 25% of their time walking, with the rest of the time spent sleeping or ruminating (Hughes & Reid, 1951)
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