Individual study: The importance of different crops as an over-winter food source for seed-eating birds in southeast England
Boatman N.D., Stoate C., Henderson I.G., Vickery J.A., Thompson P.G.L. & Bence S.L. (2003) Designing crop/plant mixtures to provide food for seed-eating farmland birds in winter. BTO Research report no. 339 (added by: Stuart F.R. 2006). Designing crop/plant mixtures to provide food for seed-eating farmland birds in winter
In the UK, seed eating farmland birds have declined in recent years with the move towards more intensive agricultural practices. Food shortages outside of the breeding season are thought to be one of the major problems affecting them. Over three years, field trials were carried out to determine which crops were of most value as a winter food source to seed eating birds generally, as well as the preferences of individual bird species.
Study sites: The study took place over three consecutive winters (1998-2001) at three different farms in southeast England: Flitcham (Norfolk; sandy soil); Royston (Hertfordshire; chalky soil); and Loddington (Leicestershire; clay soil).
Crops: Nine or ten annual crops were planted each year at each site using a randomized block design with three replicates of each crop. Four biennial crops (kale Brassica oleracea, evening primrose Oenothera biennis, teasel Dipsacus fullonum and chicory Cichorium intybus) were sown in 1998 and 1999 (but not 2000 as two years are required for these crops to mature). Table 1 (attached), lists all the annual and biennial crops grown.
Surveys: Over three winters (between October and March 1998-2001), birds were monitored at weekly intervals at each site. The observer walked along the series of plots recording the numbers of birds seen feeding in, or flushed from each plot. Surveys were carried out before 11:00 hrs, and whenever possible surveys were not undertaken during periods of rain and/or strong winds.
Annual crop species: Eight bird species were present in sufficient numbers for statistical analysis. These were, chaffinch Fringilla coelebs, goldfinch Carduelis carduelis, dunnock Prunella modularis, skylark Alauda arvensis, reed bunting Emberiza schoeniclus, yellowhammer Emberiza citrinella, greenfinch Carduelis chloris, and linnet Carduelis cannabina. With the exception of linnet, all showed non-random use of crops in at least one year.
Reed bunting and yellowhammer showed consistent preferences between years. Yellowhammer used wheat Triticum aestivum, triticale Triticale hexaploide (a crop resulting from a plant breeder's cross between wheat Triticum and rye Secale) and millet Panicum effusum. Reed bunting was recorded most frequently in crops of millet and fat hen Chenopodium album. Greenfinch made use of different crops at different times of year, with sunflower Helianthus annuus and borage Borago officinalis used in early winter and mustard Sinapis album later in the winter. The details of bird species preference for crop type can be found in Table 2 (attached).
Biennial crop species: Nine bird species were present in sufficient numbers for analysis. These were blackbird Turdus merula, song thrush T.philomelos, dunnock, goldfinch, greenfinch, chaffinch, linnet, reed bunting and pheasant Phasianus colchicus. With the exception of dunnock and reed bunting, all showed non-random crop use in at least one year. Crop preference was consistent between years, with kale being favoured by the majority of species (see Table 2).
Conclusions: The results of this study suggest, that of the crops trialed, the use of kale by a wide range of species (both passerine and game birds) makes it an excellent crop to grow as a food source to help conserve farmland birds in general, over the winter months. A mix of kale combined with other crops can be used to assist specific species, such as linseed to encourage linnet and goldfinch.
Note: If using or referring to this published study, please read and quote the original paper.