Action: Manage ditches to benefit wildlife
Key messagesRead our guidance on Key messages before continuing
- Three out of four replicated studies from the UK found that some farmland birds responded positively to the presence of ditches managed for wildlife. All three also found that some species did not respond positively or responded negatively to management.
- A replicated, controlled and paired sites study from the UK found that bunded ditches were visited by more birds than non-bunded ditches.
Managing ditches to benefit wildlife can involve reduced or delayed cutting of vegetation on ditch banks and restricted fertiliser, herbicide or pesticide use on ditch banks or in fields adjoining ditches. ‘Bunded’ ditches are blocked to allow them to fill with water.
Supporting evidence from individual studies
A replicated, controlled and paired sites study of bunded and non-bunded drainage ditches in arable and pastoral areas of Leicestershire, UK (Defra 2007), found that bird visit rates were significantly higher in bunded compared to non-bunded ditches (1.0 vs. 0.5 visits/month). Sampling involved bird observations (45 minutes, 1-2/month between April 2005 and March 2007.
A replicated study in February 2008 across 97, 1 km2 plots in East Anglia, England (Davey et al. 2010), found that four farmland birds showed strong positive responses to field boundaries (hedges and ditches) managed under agri-environment schemes. Six others showed weak or negative responses. This study is discussed in detail in ‘Manage hedges to benefit wildlife’.
A replicated site comparison of 2,046, 1 km squares of agricultural land across England in 2005 and 2008 (Davey et al. 2010) found that management of hedges (see ‘Manage hedges to benefit wildlife’) and ditches under Entry Level Stewardship did not have clear impacts on farmland bird species. Management had significant positive impacts on five species in at least region of England, but these effects were often very weak and four of the same species showed negative responses in other regions. The other five ‘hedgerow’ species investigated were never positively associated with boundary management. Generally, effects appeared to be more positive in the north of England.
A replicated 2010 site comparison study (Davey et al. 2010) of the same 2,046, 1 km² plots of lowland farmland in England as in (Davey et al. 2010) found that three years after the 2005 introduction of the Entry Level Stewardship and Countryside Stewardship Schemes, there was no consistent association between the length of ditches managed according to the agri-environment scheme on a plot and farmland bird numbers. Although there were higher numbers of linnet Carduelis cannabina and reed bunting Emberiza schoeniclus (two species known to nest in vegetation at the side of ditches) in plots with ditches managed according to the Countryside Stewardship Scheme and Entry Level Stewardship than in other plots, this difference was not observed for other species also expected to benefit from ditch management, including the yellowhammer Emberiza citrinella and yellow wagtail Motacilla flava. Between 2005 and 2008, skylark Alauda arvensis and grey partridge Perdix perdix declines were greater in plots with lengths of ditch management than other plots. For example, grey partridges showed decreases of 1.3 birds for each 0.08 km of ditch on pastoral farmland. The 2,046 1 km² lowland plots were surveyed in both 2005 and 2008 and classified as arable, pastoral or mixed farmland. Eighty-four percent of plots included some area managed according to the Entry Level Stewardship or Countryside Stewardship Schemes. In both survey years, two surveys were conducted along a 2 km pre-selected transect route through each 1 km² square.