Thursday, 27 September 2012

GPS tracking the Black eagle


Black eagles are known to occupy relatively small territories or home ranges (Davies 1994). However most estimates of home ranges have been deducted from nest spacing averages. Yesterday marked the GPS tagging of the third eagle for this study and as I am sat at my desk typing this the, first bit of data from that eagle has just come through!!

So what have we learnt so far?
The very first eagle was tagged in April this year in the Cederberg. Although the GPS device came off prematurely after only five weeks it still gave us the first insight into the actual habitat use of one of these birds. From that eagle we learnt that it used a core area of 23km2 but covered a total of 50km2 when we include data from one-off longer flights. This compares very nicely with Rob Davies (1994) estimation of a home range size of 24km2 for Black eagles in the Karoo.
Cederberg eagle tracks
The second eagle was tagged last month in the Sandveld. After only a few weeks of data thus far we have seen a much larger home range. This eagle seems to have a core range of approximately 65km2 and a total range of 92km2. It seems to make longer flights, possibly travelling further on foraging missions to remnants of uncultivated land.

Sandveld eagle tracks

And now we have the third eagle, again tagged in the Cederberg. After a long wait of 30 hours in a hide over three days, we finally made a safe capture yesterday afternoon. The eagle weighed in at 3.5kg with a 2m wingspan.

Here he is, about to be set back on his way equipped with a top of the range GPS logger!!


I look forwards to sharing data with you from this eagle. I would like to take this opportunity to thank all of the sponsors for supporting this research - without you it would not have been possible - The Cape Leopard Trust, Driehoek Wine, Darling Brew, K-Way, Cederberg Cellars, EvoSat and the Animal Demography Unit!