Upland rush management advocated by agri‐environment schemes increases predation of artificial wader nests

Abstract

Farmland birds, including breeding waders, have declined across Europe. One frequently advocated strategy to facilitate population recovery is using agri-environment schemes (AES) to improve vegetation structure. A key example is cutting dense rush Juncus to open the sward which aims to increase the abundance of wading birds, for example by improving foraging conditions. Effects on breeding success are, however, unknown. This is a critical knowledge gap as high nest and chick predation rates are a key driver of wader declines. For wader species that nest across a range of sward structures, for example Eurasian curlew Numenius arquata and common snipe Gallinago gallinago, converting denser swards to more open ones may reduce opportunities for nest concealment and thus increase predation risk. Due to the difficulties of locating large numbers of wader nests, we assess rush management impacts on nest predation risk using artificial wader nests (n = 184) in two upland areas of England, using fields in which rush is managed according to AES prescriptions (treatment; n = 21) or un-managed (control; n = 22) fields. Daily nest predation rates (DPRs) were twice as high in treatment (0.064 day À1) than control fields (0.027 day À1). Within treatment fields, DPRs were twice as high for nests in cut rush patches (0.108 day À1) than in uncut rush (0.055 day À1). Modelling links higher DPRs associated with rush cutting to the resultant shorter and less dense vegetation. Our results highlight the need to assess how AES prescriptions that alter vegetation structure impact all aspects of the target species' fitness and thus determine population recovery. Studies using real wader nests should test whether AES rush management inadvertently creates an ecological trap by altering vegetation structure, and identify the sward structure and configuration that optimizes trade-offs between foraging conditions and nest predation risk.

Inter-Specific Variation in the Potential for Upland Rush Management Advocated by Agri-Environment Schemes to Increase Breeding Wader Densities

“…Whilst our findings are not indicative of strong, and regionally uniform increases in Lapwing and Snipe breeding densities arising from rush management, they do suggest that these species are more likely to respond positively than Curlew, especially in the case of Snipe. This is perhaps logical given (1) the preference of nesting Lapwing for short, open vegetation (Baines, 1988;Milsom et al, 2000;Durant et al, 2008) that is generated by rush cutting (Robson and Allcorn, 2006;Kelly et al, 2021), and (2) smaller-and medium-bodied species (Snipe and Lapwing, respectively) may be particularly negatively impacted by taller and denser swards that will obscure their view and thus ability to detect predators (limiting their willingness to forage and nest in such habitats) to a greater extent than larger species such as Curlew (Devereux et al, 2004;Whittingham and Evans, 2004;.…”

“…Such a situation could arise either because the current prescriptions to cut onethird of the rush within a field on an annual basis are insufficient, or because such prescriptions are too difficult for farmers to follow as they feel that they should cut a larger proportion of the field when they are able to access fields for rush cutting (this is often difficult in winter due to waterlogged conditions). It is also important to note that rush cutting through AES prescriptions has been found to increase the risk of artificial wader nest predation (Kelly et al, 2021) and thus birds may be avoiding nesting in such fields due to perceived, or realised, increases in nest predation risk.…”

“…The study design is described in full by Kelly et al (2021). Field selection was performed without prior knowledge on wader use of the selected fields, and was based on fields meeting our criteria on rush management, spatial configuration and obtaining permission from landowners to conduct the research.…”

“…It could consequently restrict physical access to the soil for foraging (Devereux et al, 2004;Robson and Allcorn, 2006), and reduce waders' ability to detect predators and thus their willingness to breed and forage in such locations (Whittingham and Evans, 2004;Robson and Allcorn, 2006). Although, the taller, denser vegetation generated by increased rush cover could provide nests and chicks with greater concealment from predators (Valkama et al, 1998;Kelly et al, 2021).…”

“…These prescriptions, which typically comprise a long-term aim to reduce the extent of dense rush swards within a field to <30%, involve mowing, aftermath grazing, and occasionally herbicide application (precise prescriptions deviate slightly between United Kingdom countries; Natural England, 2012;Welsh Government, 2017;Shellswell and Humpidge, 2018). In the short-term, rush management opens up the sward and reduces vegetation height and density (Kelly et al, 2021). There is, however, little published data supporting the assumed beneficial impacts of these changes in sward structure on breeding waders.…”