For the past three years, I have been adamant that it would be impossible to re-trap a tagged vulture. The birds simply go too far – spending much of the year outside of the Mara in areas where I can’t trap – too quickly and are thus difficult to locate even when a backpack is sending you their location. Today I proved myself wrong.
Lillian is a young Lappet-faced vulture that I trapped in April of 2010. She currently has the longest working GSM-GPS unit and has been reliably sending her location four times a day for the last 16 months, giving me an incredible amount of data. Lillian has become something of a favorite as I have also resighted her more times than nearly any other bird.
After the initial trapping, we relocated her on a nest and were able to see her several times during those first few months when she was returning to her little home atop a small Gardenia tree each evening. Then in June I respotted her during some surveys in Serengeti National Park, Tanzania and starting a few weeks ago I had been seeing her every few days in the Mara.
Four days ago I saw her at a carcass with a lovely full crop, showing that despite being young she had learned how to hold her own and fight for a meal. Then yesterday I saw her sitting atop a short tree late in the evening settling in comfortably for the night. She was so low that it seemed you could almost reach her toes from the bottom of the tree and I had now seen her so many times that she seemed to be begging to be re-trapped so with the rains coming in we decided to give it a go early the next morning. The unit had stopped working about ten days previously and I figured this might be our last chance to take the unit off her.
Re-trapping Lillian would give us several advantages. For one, it would give us an opportunity to see how she was doing and ensure that the unit and backpack were not harming her in any way and perhaps improve on design for the future. It would also give us an opportunity to get the unit refurbished, far cheaper than purchase of a new unit, we could send the unit back and get a new one made from the old parts at a fraction of the cost.
Finally, we could remove the backpack. Although the Teflon straps should wear through on their own, it would likely be another year before the unit would fall off without our assistance. Thus if we could actually trap Lillian again we could take it off a bit earlier, saving her the trouble of carrying around a 100 gram weight with no working battery.
At 5 AM I was up and ready for action. Would she still be roosting in the same tree? Would we really be able to catch her? What other dangers would be waiting for us in the bush around her roost? We drove out in the dark of night, spotlight in hand with a plan that had thus far never worked. When we arrived at the tree, we untied our newest trap of choice, a long pole with a noose at the end. The idea would be to spotlight the bird so she would sit still, while looping the noose around her neck.
Then when she jumped from the tree we could carefully lower her to the ground and cut the backpack off. Last time we had tried this a pride of lions had followed us to the tree and I was a bit more wary this time as we stepped out of the car onto the dark savannah. I scanned around with the stoplight but no eyes appeared and we walked towards the tree with the pole. Everything was working well; Lillian sat calmly in the tree as I shined the light on her and my field assistant, Wilson had the noose only inches from her beak, but then she flew.
I followed her down and found myself chasing after her on foot. In the dark, it seemed likely that she would be hesitant to take off and I might be able to sneak up behind her. She leaned forward as she trudged through the grass and I was amazed at her walking speed as I stepped gingerly behind her. After several minutes of walking I turned the light off for only a second, hoping to race up and grab her in the moment of darkness, but she took off again and this time I wasn’t able to see where she went. Realizing that I was now some distance from the car we turned around and hustled back, the moaning call of nearby hyenas following us as we did.
The pole secured to the top of the vehicle we hatched a new plan to chase her while it was still dark. Now all we had to do was find her again. Given that Lillian is an 8 kg bird this might not seem so difficult, but she is also brown and can easily tuck behind a bush or into a grass tuff or perhaps strenuously flap her way back into a tree, so it took us an hour. When we finally found her the sun was just beginning to breach the horizon but it was still cool and the air was calm. Amazingly she was still on the ground and had probably been tromping around trying to avoid these unusual predators (us) for the last hour. She was already exhausted, so it wasn’t long before I leapt from the car again and found myself chasing her on foot.
Running down a bird is a rather unusual experience. She was too tired to take off but that didn’t stop her from the occasional flap and she continually turned around (swiveling her flexible head) to squawk angrily beak opened wide. For my part, I just ran paying little attention to the other animals that hustled out of our way, my focus was the bird and nothing else. Eventually I caught up to her and tossed my jacket over her head. She lay down calmly in defeat and I quickly snipped the backpack straps removing the unit. She had a few missing feathers but was no worse the wear for caring our precious device for over a year.
We had learned so much from her already but now she could go 100 grams lighter. When we pulled the jacket off she sat and stared at me, unsure how to proceed. I walked up and gave her a gentle push on the tail feathers, which was greeted with one last meager attempt at a bite. Then she was up and off again. When we came back to check on her a few hours later, we found her sitting happily at a new carcass (wing tag still attached so we could identify her). I wondered as I always do after a capture, if we would ever see her again.