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Quantifying the magnitude of the loss of set-aside stubbles and its impact on the winter ecology and distribution of farmland birds - BD1639

Set-aside was introduced in 1988 by the European Commission as a production control measure. Since 1994, the area of set-aside has fluctuated but accounted, on average, for 10% (c. 500,000 ha) of all arable land. A wealth of evidence suggests it has had benefits for farmland biodiversity, particularly birds, because it provides areas of fallow land free from pesticide and fertilizer inputs with naturally regenerating vegetation and the seed and invertebrate resources associated with such land-use. Set-aside has been shown to support higher densities of a range of bird species such as skylarks in summer and winter than a range of crop types. This has been attributed to the enhanced foraging, and for some species nesting, opportunities afforded by food-rich fallow land with sufficiently sparse vegetation to allow easy access to the soil surface. More recently, research under Defra project BD1636 has suggested that year-to-year changes in the area of set-aside are correlated with those in the Farmland Bird Index.

The loss of set-aside in 2007-08 could, therefore, potentially have negative impacts on many farmland bird species, in both summer and winter. One key habitat that rotational set-aside provided was over-wintered crop stubble, a habitat known to be an important and highly preferred foraging resource for seed-eating birds. Indeed, set-aside provided the major means by which stubbles were preserved into late winter, a period that research suggests is particularly critical for the over-winter survival of farmland seed-eaters like yellowhammer. This project is designed to estimate the change in the carrying capacity of arable farmland in winter (i.e. the numbers of birds that it can support) as a result of the loss of stubbles that would have been retained under rotational set-aside. Specifically it will:
(i) quantify the changes in bird abundance in arable farmland that occur after the disappearance of set-aside stubbles,
(ii) determine whether alternative habitats are used more now that stubbles under rotational set-aside have been lost and
(iii) determine the extent of loss of stubbles as a result of the loss of rotational set-aside in each of arable, mixed and grass-dominated landscapes.

The project capitalises on the existence of baseline data for birds and habitats in winter from two BTO studies, a regional study carried out in East Anglia under BD1628 and a national survey carried out under the BTO/JNCC Winter Farmland Bird Survey (WFBS). Under BD1628, complete winter crop coverage are available for 20 2×2km tetrads in East Anglia from 2004/05 to 2006/07. All fields in each tetrad were surveyed for birds each winter, providing estimates of total local populations of all farmland species. We will re-survey birds and habitats in these 20 tetrads twice between mid-November 2007 and mid-March 2008. These data will allow the calculation of areas, and birds supported on those areas, under (a) all stubble and (b) set-aside stubble for the post-set-aside situation and for previous winters. The existence of detailed baseline data for birds and habitats will allow us to control for changes in habitat un related to set-aside loss. This will provide detailed information on patterns of change in birds and habitats for arable farmland in East Anglia. Finally, we will attempt to gain some insight as to the relative importance of zero set aside and increased cereal prices in driving these changes through informal discussions with farmers in the study area. The generality of these patterns for birds and habitats will be assessed using the national WFBS habitat data. Under WFBS, surveys of farmland habitats in ca 800 1-km squares in English lowland recorded the areas of different crop stubbles (and other winter habitats) nationally over three winters (1999/2000, 2000/2001 and 2002/03). We will re-survey habitats in 135 of these 1-km squares, across arable, mixed and pastoral regions, that featured different areas of stubble in previous years (high, medium or low), in order to identify the extent habitat change post-set-aside.

Together, the two approaches described above will (i) provide an estimate of the area of the key stubble resource lost as a result of the loss of rotational set-aside in an area of intensive arable farming (East Anglia); (ii) provide an estimate of any changes in density of granivorous birds in arable farmland as a result of the loss of set-aside stubbles; (iii) identify which (if any) alternative habitats are being used more after the loss of set-aside stubbles; (iv) provide an indication of how well the extent of stubble loss in East Anglia reflects that seen more widely throughout lowland England. The results will help policy-makers to assess whether and, if so, how much new habitat creation or management is required to compensate for the loss of set-aside in terms of the provision of winter foraging resources for birds and thus to prevent further population declines. The results will also help to identify the kinds of habitats and management already present on farmland that provide alternative winter food resources and that could be promoted in future management measures.
Please describe the general objectives of the project and the technical and scientific aims of the research which must be measurable and timebound, (please number the objectives). If your application is accepted, these objectives will be included in the agreement between you and the Department. Please, therefore, restrict your entry to the salient points and set these out clearly and concisely.

(i) identify key options or combination of ELS options associated with high bird densities and whether these differ according to the surrounding land use (e.g. extent of semi natural habitat or grass:arable ratio)
(ii) assess the extent to which 1km squares with high ELS uptake also support high densities of key bird species relative to low uptake squares. (Whether this is attributable to the creation of ELS habitats or whether these 1km squares were also high bird density squares in the baseline year of monitoring (2005) will be assessed using wider ELS monitoring data)
(iii) provide habitat data for the entire 1km square that will serve to ground truth transect habitat data recorded under wider ELS monitoring (c. 2000 1km squares). This will allow analyses of population changes recorded in the wider monitoring to be related to habitat data controlling for biases in habitat recording (e.g. under representation of linear features such as margins on transects)
(iv) develop evidence-based recommendations for the development and deployment of ELS options in consultation with Defra
Project Documents
• Final Report : Quantifying the magnitude of the loss of set-aside stubbles and its impact on the winter ecology and distribution of farmland birds.   (1585k)
Time-Scale and Cost
From: 2007

To: 2008

Cost: £70,033
Contractor / Funded Organisations
British Trust For Ornithology
Environmental Protection              
Nature conservation              
Wildlife conservation