 A pilot study of the dispersal and behaviour of satellite-tagged Black Harriers was forged between Natural Research and Dr Rob Simmons (pictured right holding a black harrier) of the FitzPatrick Institute, University of Cape Town in 2008. Black Harriers are a globally Vulnerable species with an estimated population of only 1000-2000 birds. Their breeding ecology and threats have been intensively studied in a 10-year programme run by Simmons and Dr Andrew Jenkins, and their students have focused on the effects of habitat fragmentation and the utility of Black Harriers as indicators of biodiversity in this global hotspot.
What is unknown is (i) where they go in the austral winter and (ii) if the movement and survival away from core breeding areas is influencing their low population numbers.
The pilot study using 2 breeding birds – one male and one female – was initiated in October 2008 as both birds finished breeding. The female showed minimal movement from her nest and roost area until January 2009, when she moved 90 km north to old farmland and natural vegetation where she is currently located (March 2009). The male (named Motlanthe, shown below carrying prey to his young), has remained in his breeding area but showed large movements previously unrecorded in breeding black harriers.
Relative to the maximum 3 km recorded for radio-tagged birds and sightings of wing-tagged birds, Motlanthe averaged 11 km foraging trips in October with maximum records extending up to 50 km. Like previous studies he remained within natural heath-like habitat, avoiding farmland.
Male carrying food to his young whilst sporting his satellite transmitter. © Mark Anderson
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The greatest surprise came from night time readings showing that the male has been highly active on three occasions when the satellite data readings came at night. The latest movements indicate a roost site near his old (successful) nest and movements throughout the night of up to 10 km from the roost. On two such bouts, while still feeding young, the nights were brightly moonlit. However, on the third occasion in mid March 2009, there was a new moon and he was moving in virtual darkness. The best guess as to his activity is that he is hunting gerbils that are nocturnally active, but further research is required.
 Night-time movements of the adult male Black Harrier over the period 17-23 March 2009. Orange marks indicate locations with an accuracy < 1km, indicating he moved at least 10 km from his roost area during the night.
It is hoped that by satellite-tracking birds away from these core breeding areas we can record large scale dispersal movements into Namibia where birds are regularly sighted in the austral winter. What they are eating and how well they survive remains to be seen.
This project is managed by Dr Rob Simmons, with additional support from Natural Research, The Dogwood Fund and Hawk Mountain Sanctuary.
YOU CAN HELP THIS PROJECT!
After a successful pilot-year, we are now raising funds to purchase more satellite tags for Black Harriers in South Africa. These additional tags will provide more information about the movements of these stunning birds, which can be passed on to the policy-makers who decide which areas of land require protection. If you would like to help by making a donation, please click here to visit our donations page. Thank you for your support.
To read more about this project, please click here
 
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