The extensive spatial organization of many large-bird populations is difficult to assess. We used a geographic information system to correlate vegetation structure with random sightings for four large bird species that occur throughout the 20,000 km2 Kruger National Park (KNP), South Africa. Vegetation structure was assessed visually during 1991-1992 for the 1093 2-5′-quadrats that cover the KNP. Sightings were made during 1991-1994 of Kori Bustard Ardeotis kori, Martial Eagle Polemaetus bellicosus, Lappet-faced Vulture Torgos tracheliotus and Southern Ground Hornbill Bucorvus leadbeateri, and their nest sites. As control, comparative data on ground hornbills were also available from annual aerial censuses during 1982-1994, and from records of nest sites during 1966-1996. Each species had its highest positive correlation with a different set of vegetation categories, ranging in value from the hornbill (1.13) and vulture (1.15) up to the eagle (1.32) and bustard (1.49). Nest sites had higher correlations (hornbill 1.65, vulture 2.85) than records of free-living birds. The same vegetation categories that had the highest correlations with random sightings of ground hornbills and their nests also had the highest correlations with the more extensive and systematic data from aerial census and long-term nest records. Our method of correlating vegetation structure with random data is predictive, testable and has application to the conservation management of other sparsely distributed species.
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