A new role for pond management in farmland bird conservation

Abstract

1. Biodiversity declines in agricultural landscapes represent a major conservation challenge. In the UK, some agricultural landscapes contain high pond densities, but many farmland ponds have become terrestrialised since the 1960s, with input of organic material resulting in a decrease in the size and depth of ponds that eventually transform into wet woodland habitats. Pond management, including removal of overhanging scrub and sediment, has proven highly effective in enhancing freshwater biodiversity. However, the implications of this management for farmland bird assemblages are unknown. 2. Bird surveys were undertaken at recently managed, open, macrophyte-dominated and at highly terrestrialised, macrophyte-free ponds in the intensively cultivated farmland of North Norfolk, UK. The diversity, abundance and composition of bird assemblages visiting these ponds were compared to determine responses to pond management by tree and mud removal. 3. Avian species richness, abundance and bird-visit frequencies were all higher at open farmland ponds. The observed patterns of bird occurrence were best explained by management-induced reductions in tree shading that resulted in aquatic macrophyte-dominance likely associated with high emergent invertebrate prey abundance. Moreover, we predict that open-canopy ponds offer greater habitat heterogeneity than overgrown ponds, allowing diversified bird use. Overgrown, terrestrialised ponds were preferred by some woodland bird species. Gamma diversity across the entire pondscape exceeded all individual pond alpha diversity measures by an order of magnitude, suggesting distinct variation in the bird assemblages visiting farmland ponds during different successional stages. 4. Pond management that generates a mosaic of pond successional stages, including open-canopy, macrophyte-dominated ponds, could help to address the long-term decline of farmland birds. We strongly advocate increased agro-ecological research in this field, combined with greater emphasis on ponds and pond management options in agri-environment schemes.

Small Water Bodies in Great Britain and Ireland: Ecosystem function, human-generated degradation, and options for restorative action

“…The effects of changing habitat quality will vary according to the nature of the deterioration and some species may actually benefit, although generally not conservation-priority species. For example, ponds overtaken by scrub are poor for aquatic bird species, but provide habitat for various scrub- species, such as warblers ( Davies et al, 2016 ). Similarly, eutrophication could enhance food resources for birds that exploit emergent Chironomidae, although ephemeral flushes of invertebrate food abundance (e.g.…”

“Ghost ponds” – How to resurrect in-filled farmland ponds to assist aquatic biodiversity conservation in agricultural landscapes

“…Farmland ponds afford crucial oases within intensively managed agricultural landscapes, contributing to habitat heterogeneity (Benton et al 2003), and to aquatic and terrestrial biodiversity (Williams et al 2003, Davies et al 2016. Despite their ecological importance, over 50% of farmland ponds in the UK have been lost during the last century, with many filled in due to agricultural land consolidation (Hassall 2014).…”

Big things come in small packages: why limnologists should care about small ponds

“…Ponds have clearly been shown to have enormous value for amphibians (Beja & Alcazar, 2003;Knutson et al, 2004), invertebrates (Cayrou & Céréghino, 2005;Friday, 1987;Williams, 1997), and other groups of organisms (Davies et al, 2016;Sebastián-González et al, 2010). Soomets et al (2016) demonstrated that ponds constructed for amphibians also serve as habitat for many other Downing et al, 2008).…”