Intensive supplementary feeding improves the performance of wild bird seed plots in provisioning farmland birds throughout the winter: a case study in lowland England

Sown bird-food plots with intensive (daily) supplementary feeding throughout the winter attracted substantially greater numbers of seed-eating farmland birds than control plots without additional feeding, whose planted seed resource was exhausted by mid-winter. We studied the performance of cultivated agri-environment scheme (AES) plots, predominantly growing wild bird seed (WBS), in addressing the ‘hungry gap’ of food scarcity for seed-eating farmland birds over the winter period. We assessed whether intensive supplementary feeding could improve AES-WBS plot performance to support greater numbers of birds over a longer period throughout the winter. Five monthly bird counts were conducted from November to March on AES-WBS plots on three farms during three winters, alongside assessment of standing seed availability on the plants. Daily supplementary feeding of 8–25 kg of mixed seeds was scattered directly onto each treatment plot, with additional seed provided in hanging bird-feeders. The density of target farmland birds, and the depletion of the standing seed resource on plants, was compared between treatment plots and controls over the winter, using generalized linear models. Cultivated AES-WBS plots contained only approximately 25% of their potential full capacity of seed availability at the beginning of winter, and this was exhausted by January. Supplementary feeding attracted significantly greater numbers of farmland birds to AES-WBS plots than unfed controls, with up to 421 birds per plot, dominated by Common Chaffinches Fringilla coelebs, Yellowhammers Emberiza citronella, and Common Linnets Linaria cannabina. Bird densities on fed plots peaked in the late winter (February) ‘hungry gap’, but the magnitude of peak densities varied between years and farms. Intensive supplementary feeding can substantially improve poor performance of AES-WBS plots in supporting farmland birds throughout the winter, particularly during the late winter ‘hungry gap’ when seed availability on AES-WBS plots is otherwise exhausted.