Monitoring breeding raptor populations - a proposed methodology using repeatable methods and GIS

Poirazidis K., Schindler S., Ruiz C., Scandolara C.

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Abstract:

Monitoring raptor populations is a diffcult task, because birds of prey are wide-ranging, many are secretive and in some places very diffcult to detect. In this paper, a systematic methodology for the monitoring of raptor populations is presented. This methodology was developed and implemented in Dadia National Park, north-eastern Greece, which hosts a diverse community of birds of prey in high abundance. It was applied by WWF - Greece in the framework of the monitoring plan established in the area, aiming at the evaluation of the raptor population trends in order to promote conservation measures. From 2001 until 2005, all species of diurnal raptors, except the large vultures Aegypius monachus and Gyps fulvus, were surveyed in 34 permanent plots, and a total of 4000-6000 annual observations of 22-24 species (17-18 breeding species) were collected during March to July. The observations were used to estimate raptor species’ relative abundances and the numbers of territories. All the observations were entered in ArcGIS and the digitized observations were labelled, showing the number of individuals, age, sex, and bird behaviour under different symbols. For each species a spatially explicit territory analysis was performed, based on pre-defned criteria and the resulting breeding territories were classifed in two categories: confrmed or possible. During the study period, the total number of territories was almost stable with an average value of 350 territories. Common Buzzard was the most abundant raptor having at average 120 territories and other nine species were found to have more than 10 territories.