Due to the rarity of the bittern, accurate monitoring of the population size and breeding success is important.
The counts are based on numbers of booming males, which are individually identified by sound recording, since their voice patterns are unique.
Due to the low population size, the increased mortality during harsh winter weather can bring about significant population decline and even local extinctions. Creation of ice-free areas and supplementary feeding during severe winter weather could reduce winter mortality substantially.
How to help
The importance of reedbeds for bitterns and a range of other species such as Cetti's warbler, Savi's warbler, marsh harrier and bearded tit has been recognised for many years, and as a result, the RSPB and other conservation organisations give high priority to acquisition of reedbed reserves.
In addition to managing existing reedbeds for bitterns, the RSPB is actively working to restore reedbeds and create new ones. Reedbed improvement and restoration work is carried out on a wider scale in conjunction with several other organisations and private individuals.
Reedbed management and restoration involves several practices, including the following. Raising of water levels and keeping them high all year round. Cutting or mowing of reeds, and in places winter burning to reduce the accumulation of litter. Lowering the reedbed to allow more effective flooding. Improvements in water level control and water flow. Installation of water control structures to create optimum conditions within the reedbed.
Reprofiling and clearing of existing dykes and ditches and creation of new ditches and other open water areas within the reeds to increase feeding opportunities for the birds. Creation of links between different reedbeds and open water areas to enable fish movement between the areas. Introduction of fish to reedbeds to improve feeding opportunities. Coppicing and removal of encroaching shrubs and trees. Planting of reeds to extend reedbed area.