Only 10 per cent of more than 200 farmers interviewed believed farmland birds such as lapwings and skylarks have declined in their area, whereas 52 per cent thought they had increased. Similar results were found for populations of butterflies and bumblebees.
Among farmers who did perceive a decline, only half thought it was down to farming practices. Others cited predation, disturbance or loss of land to development.
However, the survey also found 86 per cent of farmers agreed that environmental management and wildlife conservation were important parts of farm management.
Richard Winspear, RSPB agricultural adviser and chairman of the Voluntary Initiative biodiversity group, said: "The surveys show that farmers want to do their bit for wildlife but they do not always notice declines or the reasons for them. Clearly, we need to explain this better."