The effects of the use of herbicides in cereals on the feeding ecology of partridges.

Abstract

The decline of the Grey Partridge can be explained in terms of decreased chick survival which can, in turn, be linked to changes in the abundance of their arthropod food in cereal crops.

Under favourable conditions herbicides can temporarily reduce the number of arthropods in the cereal crop to about 30% of that in untreated crops. Further reductions are associated with the decline of undersowing. With cleaner crops and fewer arthropods, aphid outbreaks become increasingly probable, and in 1970 they soon compensated for the reduction of other insects. However, if the weather. in April and May is cold the aphids cannot increase in time to be of use to the partridges. Since about 1 955 the chick survival rate has therefore been depressed by cold spring weather and this has led to the unprecedented decline of  the species.