On RSPB Hope Farm our monitoring work includes surveying both breeding birds during the summer and birds using the farm during the winter months too. The winter surveys are carried out monthly from December to February. On one morning in each month the whole farm is surveyed by a number of surveyors who are each allocated a distinct area of the farm. All birds using the farm are recorded on maps and once back in the farmhouse (after a warming cuppa and bacon butty) the maps are analysed. This analysis removes any double counting of the same birds and enables us to calculate the total number of birds for each species seen.
Why do we survey birds in winter? Many studies have shown that winter is a critical time for farmland birds. The loss of seed rich habitats such as over-winter stubbles has resulted in a reduction in the amount of seed food available to farmland birds, and this is thought to be one of the main causes of population declines in a number species¹.
However options available under agri-environment schemes can help remedy this by supporting measures that provide winter seed food including;
Image 1: Provision of winter seed food has increased winter counts of Yellowhammer at Hope Farm significantly. (Andy Hay: rspb-images.com)
At RSPB Hope Farm, we have provided a number of these measures over the years. The main source of winter food for birds is sown wild bird cover crops which were first grown in 2002; these plots are sown with seed rich species (including Wheat, Triticale, Fodder Radish, Quinoa and Millet). This winter we provided 2.5ha of this habitat in three areas around the farm and they proved very effective in attracting large numbers of birds. Over the past decade we have also looked at other methods of providing winter food, these included leaving small areas of un-harvested crops and trials of extended fallows (EF22).
Image 2: Green quinoa mix sown as a source of winter wild bird seed at Hope Farm. (Chris Bailey).
The impressive increase in our breeding bird numbers since we took ownership of the farm in 2000 has been well documented. However, the winter response to our wildlife friendly management on the farm has been even more remarkable.
The table below gives the maximum count of the farm bird index (for any of the 3 monthly surveys) for the first winter we surveyed the farm (2000/01) and the most recent winter (2014/15).
The results are staggering; six of the 16 species used to calculate the farm bird index that were absent in the first winter were present in 2014/15. All other index species have increased apart from greenfinch and corn bunting.
From this information we can produce an index that measures the average change in these species between years. For winter 2014/15 the population of these birds wintering on the farm is 581% higher than it was in the first winter of RSPB farm ownership.
The availability of agri-environment options providing winter seed food in the farmed landscape has been shown to benefit farmland birds². The Campaign for the Farmed Environment (CFE) advise that providing such habitats on 2% of the land on your farm this could make a real difference to the survival of farmland birds. After recent CAP reform the new Countryside Stewardship scheme for England will include a number of options within the ‘Farm Wildlife Package’ that can help support farmland birds over the winter. These options include winter bird food, ryegrass seed-set as winter/spring food for birds, basic overwinter stubble, enhanced overwinter stubble, brassica fodder crops and whole crop cereals. Watch this space for further information on the new Countryside Stewardship 'Farm Wildlife Package' and how it could help support birds and other wildlife on your farm.
¹ Robinson R.A., & Sutherland, W.J. (2002) Post-war changes in arable farming and biodiversity in Great Britain J. Appl. Ecol., 39, pp. 157–176
Moorcroft, D., Whittingham, M.J. Bradbury, R.B., & Wilson, J.D. (2002).The selection of stubble fields by wintering granivorous birds reflects vegetation cover and food abundance. J. Appl. Ecol., 39 pp. 535–547
Siriwardena, G.M., Calbrade, N.A., & Vickery J.A. (2008), Farmland birds and late winter food: does seed supply fail to meet demand? Ibis, 150 pp. 585–595
² Perkins A.J., Maggs H.E., & Wilson, J.D. (2008). Winter bird use of seed-rich habitats in agri-environment schemes. Agriculture, Ecosystems & Environment. 126 3-4, 189-194.
By Derek Gruar (Senior Research Assistant, Hope Farm).