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Reed Buntings Nesting in Oilseed Rape
1993-96

The effects of pre-harvesting operations on Reed Buntings and other birds nesting in Oilseed Rape were investigated in a study of 17 fields at Deeping St. Nicholas, Lincolnshire. Prior to harvest, Rape was either swathed (i.e. cut) or sprayed with a desiccant (either diquat or glyphosate) to aid harvesting.

Seven species were recorded singing in Rape on surveys between 1993 and 1996. Four of these: Sedge Warbler, Reed Warbler, Whitethroat and Reed Bunting, and one further species, Linnet, were recorded nesting in Rape in 1996. Reed Buntings were recorded nesting throughout the field, other species frequented the edges and a proportion of these birds may have nested in surrounding dykes and verges.

Pre-harvesting operations took place in the fourth week of July. Sprayed fields were harvested onaverage one week later and those that had been swathed another week after this. Reed Buntings in the study area fledged their second broods shortly after pre-harvesting operations. No Reed Bunting nests survived swathing, whilst, in contrast, all survived spraying. No nests or nestlings were lost after spraying, suggesting that exposure to the sprays was not detrimental. Reed Buntings also used Rape extensively to collect food for their young, but in spite of possible changes in food availability, the feeding rates of nestling Reed Buntings did not decrease after spraying. In comparison to swathing, spraying gave 15 extra days for birds to fledge their young. The study thus suggested that over 50% of Reed Buntings’ second broods may be saved by spraying crops rather than swathing them.

The study was funded by Zeneca Agrochemicals. More detailed results are reported on page 22 of BTO News issue number 216/217 and in the following paper in Bird Study 46:369-372.

Burton, N.H.K., Watts, P.N., Crick, H.Q.P. & Edwards, P.J. (1999) The effects of preharvesting operations on Reed Buntings Emberiza schoeniclus nesting in Oilseed Rape Brassica napus. Bird Study 46, 369-372.

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