The avifaunistic data originated from the breeding-bird atlases of Berlin (East and West), the Red Data Book of breeding birds in Berlin, and the results of the investigation “Die Brutvogelgemeinschaften Mittel- und Norddeutschlands. Grundlagen für den Gebrauch vogelkundlicher Daten in der Landschaftsplanung” (The Breeding Bird Communities of Central and Northern Germany – Foundations for the Use of Ornithological Data in Landscape Planning) (Flade, 1994).
For both atlases, the breeding-bird occurrence in Berlin was mapped comprehensively by means of a grid of squares approx. 1 km2. The survey was carried out in West Berlin between 1976 and 1983 on the basis of a grid based on geographical coordinates composed of half-minute lines of latitude and minute lines of longitude (cf. Ornithological Team of Berlin (West) 1985). In the eastern part of the city, a grid was used for which the ordnance survey maps were furnished with an 11 × 11 overlay of approximate squares (cf. Degen et al., 1988, and Magistrate of [East] Berlin, 1989). The breeding-bird mapping occurred between 1978 and 1982. Because no more current breeding bird map exists for Berlin or is planned at this time, it was necessary to make do with this database. Where no serious changes in the structure of the urban area have occurred in the interim, it can be assumed that the results are transferable to the present situation. For areas with major changes, no statements are made.
The 1991 Red Data Book of breeding birds in Berlin (Witt 1991) contains, in addition to an assignment of the species to the classes of the Red Data Book, a total list of all breeding-bird species with population estimates and tendencies for the whole city.
The work of Flade in 1994, with the aid of investigations from the period 1950 to 1989, provided, among other things, potential indicator species groups for the habitat types of Germany north of the crest of the Central Mountains, and developed methodological approaches for an avifaunistic evaluation of habitats.
For the survey of habitat types, it was necessary to use different bases for the two city halves. Uniform processing for the habitat type survey is valid as of 1992.
For West Berlin, an abundant statistical base was available. This included maps from the Species Protection Program of the 1984 Landscape Program (Care and Development Measures for Biotope Types, Biotope Development Areas), from the 1985-‘87 Berlin Environmental Atlas (Ecological Condition of Shores and Banks, Urban-Ecological Area Units, Vegetation, Valuable Habitats for Flora and Fauna, Age and Inventory Structure of the Berlin Forests, Actual Use of Built-up Areas, Inventory of Green and Open Spaces), from the 1986 Landscape Program (Biotope and Species Protection), and from the Berlin Environmental Atlas as of 1992 (Valuable Habitats for Flora and Fauna, Open Space Development since 1950). These maps were updated and supplemented with the aid of aerial photography from the aerial operations in April 1989 and in August 1990.
The statistical base used for East Berlin includes maps from the Berlin Environmental Atlas as of 1992, (Sewage Farms, Actual Use of Built-up Areas, Inventory of Green and Open Spaces, Open Space Development Since 1950, Age and Inventory Structure of the Berlin Forests, Urban Structure) and the 1993 Landscape Program draft (Biotope Types, Value of Biotopes), as well as 1991 ecological expert opinions on the Gosen Meadows and the northeastern part of Seddin Lake, and on the Karow Ponds in the former Blankenfelde and Buch sewage farms. However, data on many areas had to be supplemented with material from the above-mentioned aerial photography operations.
Some areas of Berlin, such as West Staaken, were mapped with the aid of aerial photography operations and of locally knowledgeable people. Also, areas with extensive open space losses (around the newly-built freeway in the Tegel Forest or the new housing areas in Marzahn, Hellersdorf and Hohenschönhausen) or significant use changes since 1980 (such as the newly reafforested sewage farms at Buch) had to be excluded. For this purpose, maps from the Berlin Environmental Atlas (1992), (Sewage Farms, Open Space Development since 1950) were used.