The elimination of certain weeds from cereal crop fields has reduced the population of the small insects that live on those weeds and that form a major part of partridge chicks' diet.

Since partridges are valued as game birds, records of their population are more carefully kept than those for many other birds.

Some of the weeds that are eliminated from cereal crop fields by herbicides are much smaller than the crop plants themselves and would have no negative effect on crop yield if they were allowed to grow.

Birds other than partridges that live in or around cereal crop fields have also been suffering population declines.

The toxins contained in herbicides typically used on cereal crops can be readily identified in the tissues of animals that have ingested them.