Farmland bird indicator on the basis of abundance and landscape systematization

Hoffmann J., Kiesel J.

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Information on the territory density of breeding birds in the context of land-use and biotope structures in the various landscapes are of particular value in habitat evaluation. For the development of a farmland bird indicator, abundances and populations of breeding birds should be therefore considered. For this purpose, a methodological approach was developed using the territory mapping method to get information for the agrarian landscape, and representative abundances of the breeding bird species in these areas. Development and testing of the method was done in Germany in the federal state of Brandenburg (30,000 km²) during 2005 and 2006. Starting with a GIS supported systematization and spatial marking off of the landscapes of the entire country, the agrarian landscape are defned in terms of the spatial location. Within the agrarian landscape, under particular consideration of the agricultural land use as well as the biotope structures, agrarian landscape types and agrarian landscape mosaic types are defned. In the agrarian landscape, then, proportionally to the defned landscape types, a number of 65 (1 km² - 100 hectares) study areas were chosen randomly. On the basis of the abundance data collected, as well as the area information drawn from the landscapes, the total populations of the breeding bird species are estimated. Using the Chi² Test, representative indicator species for the entire agrarian landscape as well as sub-indicators for the agrarian landscape types were selected. Through the use of target values for abundance of the indicator species, the current level of goal achievement for each of the species were calculated. From these values the farmland bird indicator was calculated. This serves to evaluate the agrarian landscape as a whole and the individual agrarian landscape types. Accordingly, in the federal state of Brandenburg, the grassland dominated landscapes feature somewhat more favourable habitat conditions in comparison to entire agrarian landscape, and are much more favourable in comparison to the arable dominated landscapes. In addition to the function as a state indicator, this farmland bird indicator can be used as a measure for the improvement and evaluation of existing agri-environment schemes.