Agricultural changes

The effects of modern agriculture on British bird-life are probably the best documented of all links between habitats and birds. 'Cleaner' fields, with more pesticides and herbicides but fewer weeds and insects, allied to a reduction in winter stubble and the practice of planting arable crops in the autumn, have led to massive falls in the numbers and distribution of many farmland species. In Cheshire and Wirral, many of those breeding species that have declined the most since our First Atlas are birds that mostly eat small weed seeds throughout the year, with invertebrates essential for their chicks: Grey Partridge, Corn Bunting, Tree Sparrow, Yellowhammer, Linnet, Skylark, Turtle Dove and Reed Bunting have all been lost from 100 or more tetrads in 20 years.

There are some signs of a turn-round in the fortunes of some of these species in recent years where some farmers have taken up options under Countryside Stewardship or Environmental Stewardship, and the UK government is committed to halting the long-term decline in the index of farmland birds by 2020. Incidentally, these species need mapping at the tetrad scale to see the fine detail of their distribution; although Skylark, Linnet and Lapwing, for instance, have shown a large population decline, their distribution has not noticeably contracted at the 10km square scale, indicating that they remain widespread but at lower density (Fuller et al. 1995), a finding that also holds good in Cheshire and Wirral.

Other aspects of agricultural management have adversely affected birds. Drainage has left fewer damp areas suitable for Lapwing, Curlew, Snipe and Yellow Wagtail, all of which have declined in the county. Early, and repeated, cutting of grassland for silage means insufficient time for any species to nest in the fields, especially Lapwings and Skylarks. Pesticides now kill many of the farmland invertebrates, probably hitting the food supplies of species like Mistle Thrush, Rook and Starling.

Thankfully, the agricultural chemicals are now extensively tested and none is known to be a direct poison to birds. The organochlorine seed-dressing used in the 1950s and 1960s hit birds like Stock Doves and accumulated up the food chain to cause breeding failures in species including Peregrines and Sparrowhawks. The rise in these raptors since our First Atlas is evidence that the pollutants are now only at low levels in the countryside.