Avian Collisions with Power Lines in Overberg

Oct 10, 2008

Mission: Survey of Eskom power lines for Blue Crane and other avian collision casualties

Date: 3 March 2009
Requesting organisation: Wildlife & Energy Interaction Group of the Endangered Wildlife Trust (EWT)
Location: Overberg, Western Cape
Pilot: Johan Ferreira

The Bateleurs was approached in late 2008 by Dr Andrew Jenkins, Research Co-ordinator of the Wildlife & Energy Interaction Group of the Endangered Wildlife Trust (EWT), asking for aerial assistance for a project supporting Blue Cranes, our national bird.  These beautiful birds have experienced a significant and rapid decline in numbers in recent decades.  Roughly half the remaining population of these beautiful birds can be found in the wheatlands of the Overberg, where, thanks to their limited manoeuverability and habit of flying in poor light conditions, they are particularly prone to collision with overhead power lines.   Johan Ferreira, one of our most supportive volunteer pilots in the Western Cape, offered to fly researcher Jessica Shaw to survey power lines in the wheat fields of the Western Cape.  This is the report we received from Jessica:

“The objective of the flight was to survey Eskom power lines for Blue Crane and other avian collision casualties. This will aid in the ground truthing of a previous study to identify high risk lines, which will hopefully facilitate the implementation of mitigation measures.

Having started survey work, I quickly realised how time consuming data collection on foot can be, especially in trying to contact landowners to gain access for my survey. I have also been very unlucky with the late wheat harvest this year, which has restricted access to wheat fields and visibility of carcasses in them. Therefore, the Bateleurs flight was a fantastic
opportunity to get a broad overview of the area, and to identify carcasses and collision hot-spots worthy of more intensive ground surveying for the rest of my study.

I met Johan Ferreira at 06h15 at Stellenbosch Airfield, and we were really lucky to have good flying weather.  After a quick discussion of the route, we were soon airborne. Descending
over Botrivier to begin the survey, we found a good speed and height to maximise the visibility of carcasses, with Johan helping me to search when he could. As we continued along the route we circled back for another look whenever we saw anything that could have been a collision victim, and marked the spot with a GPS for future reference. In this way, we came across a number of potential collision victims, although some turned out to be
large pieces of rubbish or rocks!  By the time we got to Bredasdorp, I wasn’t feeling so well from watching the powerlines zip past below us, and Johan kindly landed the plane so that I could recover a bit. We then flew on towards Slangrivier before heading back via Riviersonderend and Greyton, landing back at Stellenbosch at around 10.45am.

Overall, we managed to cover a large section of both distribution and transmission lines in the Overberg, far more than I could ever hope to cover on foot.  This type of survey work had not been attempted before and whilst we didn’t observe many powerline
casualties, this was probably because older carcasses are very difficult to identify from the air.  However, we saw plenty of live Blue Cranes as we flew overhead, and the flight
has been extremely valuable in highlighting areas for future ground work for me.

Whilst it was disappointing not to be able to identify more Blue Crane carcasses from the air, the flight was very successful in gaining an overview of the Overberg area.  This will inform my selection of ground field sites going forward, in terms of ease of access in the more pasture-dominated areas, and from the potential carcass sightings made.”

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