In Europe, the active contribution of farmers to nature conservation is mainly voluntary. Whereas participation in agri-environmental schemes (AES) has been studied in detail, less is known about self-initiated nature conservation. Given the alarming decline in species diversity and abundance in agricultural landscapes, it is important to explore this form of conservation in more detail. In this paper we report on the results of a survey of Dutch dairy and arable farmers. We conclude that a large majority of farmers conduct self-initiated conservation activities on their farmyards and fields with varying ecological impacts and impacts on farming system. Helping birds was the most often mentioned activity. Farm size, on-farm side activities (in dairy farming), organic farming, the quality of the surrounding area and the absence of external constraints have a positive effect on the number of activities. Intensity has a negative effect on both the number of activities and on the probability that farmers conduct activities with substantial ecological impacts. There is no unambiguous evidence of a ‘crowding-out effect’ due to participation in AES. More research in this area can help contributing to a maximal exploitation of the conservation potential by farmers and to creating synergies with agri-environmental policies.