Research finds simple solution to save our corn buntings

Guest blog by Rosemary Setchfield, Conservation Scientist, RSPB Centre for Conservation Science

RSPB research has shown that areas near field edges with extra crop seed frequently attract corn buntings to nest. However a nest near the edge of a field is more at risk from predation and is less likely to produce fledged chicks. Through adding more seed in the middle of the field, corn buntings could be encouraged to nest away from field edges allowing more nests to fledge chicks. This is at little extra cost and effort for the farmer and the measure is now recommended in the Countryside Stewardship scheme as a Threatened Species Advisory Measure.

“Farmer’s bird” disappears

Corn buntings were the quintessential ‘farmer’s bird’ in former decades. The endearing song of the male rattled around cereal crops all summer and busy flocks visited grain stores during winter. But today, farmers barely know this bird. Along with many other farmland birds, it has disappeared from most farms during the last four decades.

Listen to the wonderful jangly song of corn buntings (and skylarks). This sound has been disappearing from our fields for the last forty years (Xeno Canto)

Eastern England is still a stronghold of corn buntings in Britain. They typically breed in cereal fields where crop plants, including wheat, barley and oats, have stiff stems and abundant leaves for protecting and concealing nests on the ground. Intensive cultivation and years of herbicide use has removed most weeds from the crops, so females rely heavily on the cover of crop plants alone to protect their nest.

Photo of corn bunting male singing in a wheat crop (RSPB images).

Joint funding from Natural England has enabled us to investigate exactly what limits the number of corn bunting chicks produced from nests in autumn-sown cereal crops. This is what we have found:

Thick areas within crops are selected for building nests

Our data shows that females prefer to lay their clutches in parts of fields where the crop grows thicker than elsewhere. These areas probably help conceal females from predators when they are sitting on eggs or chicks.

Photo of corn bunting nest in winter wheat crop with five chicks (Rosemary Setchfield).

Thick crops near crop edges attract nest predators

Farmers often sow more crop seed near field edges, known as ‘seed overlaps’ or ‘double drilling’, which is due to the technological constraints of farming machinery. Female corn buntings are attracted to these areas for building nests because thicker crop develops, and this thickness is hard to find elsewhere in fields. We found that nests close to crop edges are more frequently targeted by predators than nests in field centres, particularly in the later summer months. This is when females produce second (or even third) clutches, so many of these nests produce no chicks.

Thick crops encourage more second clutches

Corn buntings, like many other ground nesting birds such as the skylark, should normally produce more than one clutch each summer. This ensures that enough chicks survive to breed in the following year. Along with our previous research in Cornwall, we found that crops that were thicker overall or had dense weed growth, allowed more females to produce second clutches. This is probably because thicker vegetation can better conceal females and nests from predators late in the summer, at a time when crop leaves are withering.

Designing an effective solution for corn buntings

These findings suggested a cheap and easy farmer-friendly solution to boost numbers of corn buntings fledging the nest. If extra seed produces thicker crop and attracts females to nest, then farmers could intentionally sow more seed in areas away from dangerous crop edges. If females then select these areas for nesting, many more chicks could be produced each summer because these nests would be less vulnerable to predators and females might be encouraged to produce more second clutches. An experiment has already shown that this is possible, and we are currently running final trials to confirm the full benefits. 

Aerial photo of a strip sown with extra seed by a farmer for corn buntings (Andrew Asque). Taken in autumn, humans have difficultly seeing these areas in the summer.

Predicting recovery with a solution

An important part of our work was to build a model for predicting corn bunting population increase using this new solution, made possible because we understand both why females choose to nest close to crop edges, and how nest survival changes in time and space. Our model allows us to calculate how many chicks each female could produce each summer on average when extra seed is sown at increasing distance from crop edges. From this, we expect populations to rise if extra seed is sown about 100m from crop edges, as long as females happily nest at this distance. This is what we are currently testing.

A brighter future for corn buntings?

Although final trials are still underway, this solution has already been adopted in the new Countryside Stewardship scheme as a Threatened Species Advisory Measure. Farmers are happy to sow extra seed in their fields as it is cheap, easy, and does not affect their yield or the tidiness of their crop. We have also shown that extra seed can reduce the growth of blackgrass, which is enemy number one for most farmers. So, with creative advocacy, there may even be scope for farmers to provide this management voluntarily. This offers new hope that landscapes once occupied by this enigmatic farmer’s bird can again, one day, be restored to full song for future generations to enjoy.

Please read the paper: ‘The influence of crop tiller density on the breeding performance of a cereal-nesting specialist’ published in the Journal of Applied Ecology to find out more about the research project.

Find out more about our work to test farming solutions to reverse corn bunting population decline in England here.

This work is funded by the Action for Birds in England partnership between RSPB and Natural England.