David Kleijn and colleagues report (Nature 413, 723–725; 2001) that a Dutch scheme designed to improve agricultural grasslands for wading birds had failed — more birds were found on nearby conventionally managed grass fields — and call for scientific monitoring of the effects of similar schemes elsewhere.

Just this type of monitoring programme is being conducted in the United Kingdom, showing that the 'wild bird cover option' — the growing of certain crops on set-aside ground to benefit declining farmland bird populations — can indeed be successful.

The Game Conservancy Trust and the British Trust for Ornithology, supported by the Department for Environment, Food and Rural Affairs (DEFRA), are monitoring various crop mixtures sown on more than 100 farms across southern and central England, with the aim of determining which crops are preferred by the many species of birds encountered. Experimental work will confirm birds' preferences and inform on the amount of cropping needed. Similar work is under way in Scotland.

So far, the findings show that all crop types studied support densities of farmland birds that are orders of magnitude higher than nearby conventional fields, with the biennial brassica kale (Brassica napus) and quinoa (Chenopodium quinoa), a member of the the beet family — both seed-bearing plants — being the preferred crops for most birds. Given suggestions that the decline of farmland birds could be due to the recent loss of over-winter food supplies, the implementation of prescriptions such as 'wild bird cover' could have a major impact on bird populations in the United Kingdom and, no doubt, elsewhere.