Survey evaluation for species richness of farmland birds

Abstract

To estimate biodiversity it may be important to establish whether increased data can be obtained from repeated surveys. Bird species richness was determined after repeated surveys in winter and in the breeding season. Data were collected over two breeding seasons and two winter seasons at nine sites, with three surveys in each winter and four surveys in each breeding season using a standard method. Poisson models were used to determine differences in total cumulative species richness recorded after each additional survey. There were significant increases in species richness in winter between survey one and survey two and between survey two and survey three across nine sites. There was a significant increase between survey one and survey two for resident breeding species richness. Based on pure species richness, three surveys recorded at least 95% of the total observed species richness recorded after four surveys in the breeding season within the agricultural survey area.