Wesołowski T., Czeszczewik D., Mitrus C., Rowiński P. 2003. Ptaki Białowieskiego Parku Narodowego. (Birds of the Białowieża National Park). Notatki Ornitologiczne 44: 1-31.

The Białowieża National Park (105 km²) protects the largest fragments of the European lowland primaeval forests. The paper synthesises the results of field research conducted in the whole BNP in 1999-2001, ones of a 25-year quantitative study in the BNP strict reserve, and historical data. A complete list of birds occurring in the BNP, the spatial distribution and habitat requirements of breeding species as well as some quantitative data are given. A comparison has been made between the occurrence of particular species in the strict reserve and in the incorporated, formerly managed, part of the Forest. Occurrence of 145 bird species, including 117 breeding or probably breeding, has been ascertained. Ninety species (84%) are indigenous to forest interior and margins, which indicates a relatively low level of anthropogenic deformation of this avifauna. The remaining ones are species of meadows and fields, having arrived after deforestation of the river valleys. The strict reserve, which covers a forest of pristine character, has the least altered composition of birds. Many species commonly nesting in clearings and plantations of the managed parts of the Forest (also in the new part of the BNP) are confined here to the forest margins. A typical character is low abundance of birds: 68% breeding species have fewer than 100 pairs. The BNP is a breeding habitat of many endangered species of birds, particularly those dependent on the presence of dead wood and tree holes (woodpeckers, owls and other rare hole-nesters). The abundance of the majority of them in the managed BNP section is substantially lower. To make their population recover, it is necessary to reconstruct the resources of dead wood and tree holes in the new part, and also to protect the whole Białowieża Forest.