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Effects of Agricultural Practices on Field Use by Invertebrate-Feeding Birds in Winter
G. M. Tucker
Journal of Applied Ecology
Vol. 29, No. 3 (1992), pp. 779-790
Published by: British Ecological Society
Stable URL: http://www.jstor.org/stable/2404488
Page Count: 12
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1. Farmland in Britain supports large populations of invertebrate-feeding birds in winter. However, little is known about the effects of agricultural practices on the birds' use of individual fields or their food resources. This study aimed to assess the effects of farming practices on field choice by wintering birds in an area of mixed farmland in the Vale of Aylesbury, England. For methodological reasons, birds smaller than redwing (Turdus iliacus) were not considered. 2. Permanent grass fields supported the highest densities of most of the invertebrate-feeding birds and were preferred throughout the winder. Cereal stubble and ley fields supported moderate densities of some birds but were generally avoided. Bare till, winter cereal and oil-seed rape fields were little used. 3. Soil macro-invertebrate densities were highest in permanent grass fields. The biomass of earthworms and other invertebrates was significantly higher in permanent grass than all other field types except ley. It is probable that the birds' preference for permanent grass fields is caused by the high density of food resources. 4. For most species of birds, the likelihood that permanent grass fields would be used was consistently higher where farmyard manure was applied frequently and where the grass was long established. Densities of Lumbricidae and Coleoptera were positively correlated with the age of grass but not with the input of farmyard manure. The greater number of birds observed was possibly a result of increased surface activity of earthworms. 5. The use of cultivated fields by birds was also associated with high frequencies of farmyard manure application. In these fields earthworm densities were positively correlated with input of farmyard manure.
Journal of Applied Ecology © 1992 British Ecological Society