Can agri-environment schemes halt and reverse corn bunting declines in eastern Scotland?
Corn buntings are a UK BAP priority species, having declined by 88 per cent between 1967 and 2010.
A farmland specialist favouring open landscapes, nesting on or close to the ground usually within crops, corn buntings have a seed-based diet supplemented in summer by insects. In Scotland, the population is now as low as 800 territorial males, with most concentrated in the mixed and arable farming areas of the eastern lowlands, from Fife and Angus in the south to Moray in the north.
Land management through agri-environment schemes that provides food and nesting habitats for corn buntings is the main mechanism that could lead to population recovery. Therefore, we need to monitor the effectiveness of such schemes, identify the best management options for corn buntings, and recommend further improvements where necessary.
- To determine whether land management through agri-environment schemes is associated with recovery of corn bunting populations, by comparing changes in numbers over several years on farms in Scotland's main scheme at that time, the Rural Stewardship Scheme (RSS), with 'control' farms not in the scheme. Population response to management targeted specifically at corn buntings, on farms participating in RSPB East Scotland's Farmland Bird Lifeline (FBL) project, was also measured.
- Additional field-studies and analyses of existing long-term datasets will also inform the design of agri-environment measures for corn buntings.
Key dates so far
- Improved our understanding of the species' ecology and requirements.
- Demonstrated that targeted agri-environment measures can reverse local corn bunting population declines.
- Developed a new, improved delayed grass mowing option to protect nests, and contributed to creation of a corn bunting 'package' of options within the current Scottish agri-environment scheme (Rural Development Contracts - Rural Priorities).
- Estimated the cost and scale of intervention required to halt the species' decline in Scotland.
- Raised the profile of the species amongst farming community and policy makers.
- Seven scientific papers published and PhD thesis completed.
Work planned or underway
Monitoring ran from winter 2002/03 to summer 2009, involving 71 farms in Aberdeenshire, Moray, Fife, Angus and Inverness-shire.
Winter surveys looked at habitat use by corn buntings and other seed-eating birds, to determine their use of agri-environment management options. Summer surveys from 2003 to 2009 counted the number of corn bunting territories on each farm, and mapped their positions in relation to management options and other habitats.
Other species of conservation concern such as yellowhammer, reed bunting, grey partridge and tree sparrow were also recorded. Additional monitoring of nest site selection by corn buntings in 2004 to 2009 determined the timing and success of nesting attempts, and which habitats were favoured, and existing long-term datasets were analysed to inform the species' conservation.
During winter, corn buntings and other seed-eaters including yellowhammers, reed buntings, tree sparrows, linnets and grey partridges made great use of 'unharvested crops' provided by agri-environment schemes (RSS and FBL). These crops are grown to provide winter seed for birds, and are typically mixtures of cereals and brassicas such as kale, sown in plots of 1-2 ha and left standing for one or two winters.
Crops were much more attractive to cereal grain specialists such as corn buntings and yellowhammers in their first winter of establishment. By their second winter, the main seeding plant was kale, which attracts finches such as linnets, but not buntings. Therefore, where corn buntings are targeted, we recommend annual sowing of cereal-based one-year crops, or sowing more than one patch of two-year crops in alternate years, to ensure that cereal grain is available in each winter.
Outside of schemes, cereal stubble was the main habitat used by corn buntings in winter.
During the breeding season, corn buntings laid up to three clutches from mid-May to mid-August, mostly in grass or cereal swards 30-110 cm tall. In early summer, tall crops such as autumn-sown cereals and grass silage were favoured, but from late-June onwards they switched to nesting in spring-sown cereals as these crops also matured.
Weedy cereals were especially attractive, as the weed plants provide nest concealment by forming a dense ground layer within crops, and host a wide range of insects essential for rearing chicks. In north-east Scotland, most cereals are spring-sown and not harvested until late-August/September, late enough for most corn bunting broods in these crops to fledge successfully. However, intensive monitoring showed that almost 40 per cent of first nesting attempts by corn buntings were in grass silage, and most were destroyed by mowing in June to mid-July.
One RSS management option paid farmers to delay grass mowing until 1 July, but many nests are still in use at this time. Therefore, we trialled a refinement to this option with mowing delayed until 1 August. Nest success increased from 3 per cent in fields with conventional mowing dates in June – early July to 28 per cent in fields not cut before 1 August, and losses to mowing were reduced from two-thirds of nests to just 5 per cent. This option is now available to farmers in corn bunting areas in Scotland through the national agri-environment scheme, and its widespread uptake has the potential to raise breeding success sufficiently to halt and reverse population declines.
Population monitoring has shown that between 2003 and 2009, the number of territorial male corn buntings in summer increased by 5.6 per cent per annum on farms with targeted agri-environment management (FBL), showed no significant change on farms in the non-targeted RSS, and declined by 14.5 per cent pa on control farms.
Agri-environment options most likely to have benefited corn buntings on scheme farms are unharvested crops (cereal-rich crops sown annually each spring), delayed mowing of forage grasses until 1 August, extensively managed ‘weedy’ spring-sown cereals, and grass margins around arable fields. We estimate that to halt the national decline, targeted agri-environment management of 500-600 ha of farmland is needed, costing £120 000 per annum. This equates to 0.02 per cent of annual subsidies paid to Scottish farmers, and 0.5 per cent of land in the remaining mainland Scotland range of corn buntings.
Who to contact
Scottish Natural Heritage (SNH)
University of Edinburgh
Dr Adam Watson