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Keywords:

  • Africa;
  • evidence-based conservation;
  • geographic range change;
  • Kori Bustard;
  • Otididae;
  • population decline;
  • tropical

Abstract

Aim

With the exception of South Africa there are no systematic, long-term, large-scale bird monitoring programmes in Africa, and for much of the continent the most comprehensive available data for most species are incidental occurrence records. Can such data be used to assess range-wide conservation status of widespread low-density species? We examine this using Kori Bustard Ardeotis kori, a large, easily identifiable species with an extensive African range.

Location

Southern and East Africa, 14 countries.

Methods

A comprehensive and systematic review of published and unpublished sources provided 1948 unique locality records spanning the years 1863–2009; these included 410 non-atlas records and 97 historical (pre-1970) records. Range-size changes were examined by comparing minimum convex polygons to quantify Extent of Occurrence pre- and post-1970, and by testing whether more historical records fell outside the recent (post-1970) 95% probability kernel than expected by chance. Additionally, qualitative evidence of changes in abundance was obtained from historical published accounts and contemporary assessments by in-country experts.

Results

Since the late 19th century, range-size (measured as Extent of Occurrence) has contracted, by 21% in East Africa and 8% in southern Africa. There is strong qualitative evidence of considerable pre- and post-1970 population declines in all range states, except Zambia (slight increase) and Angola (trend unclear). In some countries, declines occurred from the early 1900s. Thus, while relatively modest change in range-size has occurred in over 100 years, numbers have greatly reduced throughout the species’ range.

Main conclusions

Our methodology allowed objective appraisal of continent-wide Kori status. Despite lacking quantitative population estimates and trends, and poor understanding of the species’ autecology, common issues for many African species, incidental occurrence records can be used to assess range-wide changes in status. We recommend that this or similar approaches be applied to other widespread low-density species that probably also have rapidly declining populations despite apparently stable range extents.