Defra - Department for Environment, Food and Rural Affairs.

Science Search

Science and Research Projects

Return to Science Search homepage   Return to Project List

Scoping study to investigate the development of a chick food index - PS2358

The majority of birds breeding on farmland feed their young on invertebrates as these provide the necessary nutrients essential for chick growth and development, whilst also supplying the energy required to resist chilling (Southwood & Cross, 2002). Invertebrate food supplies within crops can therefore have an impact on chick survival and thereby on recruitment and population size. The level of invertebrate chick food has been linked to grey partridge chick survival and consequently to the decline of the grey partridge Perdix perdix (Potts, 1986). These studies also revealed that some invertebrates are more important to chick survival than others and led to the development of a chick-food index (CFI) for the grey partridge. In the index each of the five most important invertebrate groups are multiplied by their own correction factor according to their importance to chick survival. The availability of chick food insects was also found to affect the breeding success of skylarks Alauda arvensis, corn bunting Miliaria calandra and yellowhammer Emberiza citrinella (Brickle et al., 2000; Boatman et al., 2004; Hart et al., 2006), although in these cases relationships were based upon uncorrected numbers of invertebrates. Pesticides can directly and indirectly determine invertebrate numbers within crops. In this project we propose to identify whether it is possible to develop a generic chick food index that would be widely applicable to a range of insectivorous farmland bird chicks, as an indicator of the availability of invertebrate food for crop-feeding birds. We will review the diet of farmland bird species known to forage in crops during the breeding season to identify candidate invertebrate taxa. We will then compare selected taxa to those in existing indices to determine how well they reflect the requirements of all farmland birds. This would be achieved using existing knowledge of farmland bird diets and databases of invertebrate abundance within crops. Invertebrate abundances fluctuate between years and therefore a new indicator may only be immediately useable if based on existing long-term data (>5 years). We will therefore review current invertebrate monitoring schemes to determine their coverage of candidate taxa and their suitability; the latter to be evaluated by examining their historical continuity, ability to detect short and long-term changes, and proven relationships to birds or pesticide usage. In order to investigate the potential for using an existing long-term dataset to generate a chick-food index we will conduct analyses of data from the Game and Wildlife Conservation Trust Sussex Study, which is one the most comprehensive studies of the effect of changes in farming practices on farmland birds. These analyses will include the calculation of relative “biomass” based indices from yearly crop means, as well as number-based indices. The resulting report will not only compare the different possibilities open to policy makers for developing a generic chick-food index but also demonstrate the extent to which this can be done using a monitoring programme already in place.
1) Identify an appropriate chick-food index for relevant farmland bird species i.e. those for which invertebrates within commercial crops are likely to be the key food source for their chicks.
2) Identify what data are required to populate the index and how this would need to be collected to ensure they would be able to reflect changes in crop production methodologies.
3) Review options for utilising existing schemes compared to developing a new scheme.
4) Consider how existing programmes could be maintained to ensure longevity and access.
5) Demonstrate, through the use of a readily available dataset from one long-term monitoring scheme, the calculation of a reliable chick-food index across a range of farmland birds.

Project Documents
• Final Report : Scoping study to investigate the development of a chick-food index   (245k)
• Final Report - Annex : Scoping study to investigate the development of a chick-food index - annex 1   (338k)
• Final Report - Annex : Scoping study to investigate the development of a chick-food index - Annex 2   (512k)
Time-Scale and Cost
From: 2010

To: 2010

Cost: £16,134
Contractor / Funded Organisations
The Food & Environment Research Agency
Environmental Effects              
Pest and Weed Control              
Pesticide use              
Plants and Animals              
Fields of Study
Pesticide Safety