One of the key components of livestock farming system sustainability is their ability to ensure efficient production while preserving biodiversity. Whether this relationship depends on production intensity is still under debate. Surprisingly, most studies linking agricultural production with biodiversity focused on yield as a surrogate for production intensity. Indeed, livestock production relies on complex technical choices which cannot be reduced to a simplistic opposition between management techniques generating more or less yield. Production intensity should be thus described as a process articulating at least the level of inputs and outputs. This paper reports the results of a study aimed at (i) developing production intensity indicators based on input/output ratios (ii) modelling their relationship with biodiversity. Two France-scaled databases were used in order to account for the whole intensity gradient of livestock farming systems. With the Rural Development Watch we built geo-referenced indicators of production intensity. With the French Breeding Bird Survey database we constituted a study set of 25 species of farmland birds. Indicators derived from both databases were combined to model the response of birds to production intensity. Production intensity had contrasting effects on birds among regions and livestock farming systems. In contrast with theoretical bird responses already proposed by different authors, non-linear responses and threshold functions were expected i.e. birds’ populations were not affected until a threshold intensity inducing severe detrimental or beneficial effects. On the basis of these relationships, we discussed the strengths and weaknesses of the production intensity indicator in relation with its use for the environmental certification of livestock farming systems.