Autumn-sown green manure crops for nesting corn buntings Emberiza calandra: management trials in North East Scotland (UK), 2021–2023

Corn bunting Emberiza calandra is a UK red-listed species that requires significant conservation effort within agricultural landscapes to maintain populations. Its preference for nesting in cereal fields and other crops puts it at considerable risk from farming operations. In North East Scotland, where most cereals are spring-sown and nesting attempts in May and June are often in the taller denser swards of grass silage fields, nest destruction during mowing is a major problem. Delayed mowing increases nest survival rates, but also lowers the quality of forage so has limited uptake in agri-environment schemes. Potentially a more attractive solution to farmers are ‘green manure’ crops, which involve growing plants with nitrogen-fixing and other properties to improve soil condition in arable fields. These crops are becoming increasingly popular amongst farmers, but in North East Scotland are usually sown during spring. To test whether autumn-sown green manure would provide an attractive, safe nesting habitat for corn buntings in May and June the following year, we conducted a trial across six farms in 2021–2023. Results confirmed that sowing in September enabled the crop swards to become sufficiently tall and dense to attract nesting corn buntings the following spring. Furthermore, average nest survival rates in the trial plots (60%) were similar to those in cereal fields later in the season (70%), and much higher than grass fields (25%). We conclude that autumn-sown green manure crops can provide a safe alternative to grass silage fields during late spring to early summer, when corn buntings have few other nesting habitats available.