Factors affecting nest‐site choice and reproductive success of Curlews Numenius arquata on farmland

Nest‐site choice and reproductive success of Curlews Numenius arquata in different habitats were studied at a mixed farmland site (grasslands and flooded tilled fields relatively common) and at an arable farmland site (dry tilled fields more dominant than at the mixed site) in central Sweden. At both sites Curlews preferred to nest on grassland and fallow fields, where hatching success was higher than on tillage fields. Nests were also situated further away from forest edges than random sites, but hatching success did not vary with distance to the forest edge. Only 35.6% of the pairs were estimated to hatch young. The main cause of nest loss was predation and the second most important factor was destruction by farming practices, which was an important factor in tillage early in season. Surprisingly, nest survival was higher at the arable than at the mixed farmland site, probably being an effect of the increased proportion of fallowing during recent years. Mortality of chicks was 79.7% before fledgling age (both sites combined) and, surprisingly, chick survival was lower on meadows than on arable fields and leys. The mean production of young was only 0.25 fledglings per pair, which is lower than in areas less affected by farming practice. The low production of young is probably an important factor in the decline of Curlew populations on Swedish farmland. On bogs 1.4 fledglings per pair were produced, indicating that reproductive success of Curlews is higher in more natural habitats.