Breckland is one of the most important parts of the UK for breeding Nightjar Caprimulgus europaeus, one of the species for which the area was designated a Special Protection Area. However, the local population of this migratory bird fell by a third between 1998 and 2010 against a national trend of rising numbers. This paper presents the findings of a study undertaken to try and identify the reasons for this decline and specifically consider the significance of Breckland grass heaths and their associated moths for Nightjars.