The reasons for waterfowl research, monitoring and protection are the continuous deterioration of the wetlands, the increasing frequency of oil spills in water bodies, and the necessity to regulate bird hunting. Large quantities of waterfowl often assemble in the wintering sites. The research of such assemblies is the most rational way for the estimation of the quantity and the condition of the bird populations. Mid-winter waterfowl censuses have been carried out in Estonia since 1967. The project is interantional, and in 1995 it was included in the Estonian national program of biological monitoring. 

The success of the project owes a lot to a simple questionnaire that has routinely been used over a long period of time. Every year, the observers have been provided with a summary of the previous year’s census results. Both transect and point censuses have been used. On the coastal areas the wintering waterfowl has been counted from plane and helicopter as well. 

Since 1995 the permanent monitoring sites have been:

1) all the inland water bodies where the number of the wintering waterfowl (predominantly mallards) is permanently greater than 100 individuals; there are about 40 to 50 such sites;

2) the coastal sectors of the Baltic sea that do not freeze on normal winters and other sites that are known to be important wintering areas for waterfowl; there are about 100 such sites.