Cape Town - When Dr Rob Simmons gets up each morning, the first thing he does is switch on his laptop.
Nothing unusual about that, of course – millions of people the world over do something similar at the start of their days, checking e-mails, reading the news on-line, finding out the latest about Justin Bieber throwing eggs at his Los Angeles neighbour’s house…
But Simmons, a researcher at UCT’s Percy FitzPatrick Institute of African Ornithology, is looking at something profoundly more interesting and exciting – he’s watching the curtain being lifted on the hitherto secret migratory paths of the Black Harrier, an endangered southern African endemic bird (it occurs naturally only here) of which there are only an estimated 500 or fewer breeding pairs still in existence.
Until very recently, the movements of this graceful, medium-sized raptor (bird of prey) outside of its five-month winter breeding season in the coastal and mountainous regions of the Western Cape were a mystery to science, as were the reasons for mortalities during this time.
Now, thanks to technological developments that have allowed biologists to attach tiny GPS trackers weighing just 12.5g to birds and animals, scientists like Simmons and his research colleagues and associates are able to follow, in real time, creatures like the Black Harrier with an incredible accuracy of down to just 3m.
Earlier technology satellite trackers, slightly lighter but less accurate with a best resolution of perhaps 150m and providing fewer readings, are also still in use.
Simmons can now tell virtually what bush his target bird might be perching on, how fast it’s been flying, in what direction and the temperature at the time. And some of the results are proving surprising.
This species has been the subject of a 14-year research project that Simmons, formerly the national ornithologist of Namibia and now “Black Harrier species guardian” for BirdLife South Africa, started with colleagues Dr Andrew Jenkins and Dr Odette Curtis at UCT.
“The bird was just falling through the cracks then,” he explains.
Early work by Curtis and other students showed each pair of Black Harriers needed about 100ha of pristine vegetation in order to breed successfully and that these breeding areas coincide with a high species richness of small mammals like mice – their major prey – and a greater abundance of small birds, which are also taken.
But the bird’s presence could not be similarly associated with plant richness, a finding the researchers had been hoping for.
“So we couldn’t say that it is a complete indicator of biodiversity,” said Simmons.
Despite this intensive research, they still didn’t know where these birds went after breeding. So in 2008, they initiated a pilot tracking project that involved fitting satellite transmitters to the birds with a Teflon harness. Now, in a more intensive phase of the project, another six birds have been fitted with tags.
Tags are expensive, at about $3 000 (R32 500) each but, fortunately, the project has received generous sponsorship, with sponsors in turn getting naming rights. Their birds include Lockie, Cade, Cory, Kwezi, Karma and Moraea.
Six birds were caught in November by French researcher and expert trapper Dr Francois Mougeot, assisted by PhD student Marie-Sophie Garcia-Heras. He used both a dho-gazza net – a trapping technique used for centuries in falconry – and a bal chatri trap, which is cage-baited with a conspicuously visible live rodent or small bird and with a series of monofilament nooses attached to the surface that snare the legs of any raptor that attempts to take the bait, without injuring it.
Two of the female project birds have, separately, been tracked from the West Coast region of the Cape “streaking” across the Karoo, covering 1 000km in just four days, and both then headed up into Lesotho through the Sani Pass area. One of them, Lockie, continued up past the Katse Dam, and then further westwards into the Free State grasslands, covering more than 1 600km in total before meeting a tragic end, possibly after a powerline collision. The other, Moraea, has been tracked over two successive seasons to exactly the same place in eastern Lesotho, on the Mokhotlong River.
“We think they’re timing their trips for the rains that arrive in Lesotho in March and April, because this is also when the ice rats are breeding there, and the females (Black Harriers) are arriving just in time for that,” Simmons said.
“These rats are like miniature dassies, sunning themselves, and are quite easy to catch.”
The same bird, on leaving Lesotho for the first time, flew back via Engcobo in the Chris Hani District of Transkei and Aberdeen in the Great Karoo, all the way to the West Coast National Park at the start of the next breeding season.
But she spent just half a day in the park. “She obviously didn’t like what she found,” Simmons suggested.
She then headed east again via Beaufort West to Aberdeen, where she bred in the Camdeboo mountains, and she repeated this behaviour two years in a row.
“Her new nest is 550km away (from the park), highly unusual behaviour for a raptor. It’s the only raptor we know that is breeding in an entirely different habitat – West Coast strandveld, compared to the dry Karoo vegetation. That was her last signal, unfortunately, but she’s given us some amazing data.”
Three of the Black Harriers – Kwezi, Cade and the as yet unnamed UCT001 – have bred on the very hot interior plains in the Vanrhynsdorp area, before also flying at speeds of over 60km/h across the Karoo in virtually a straight line to the Winterberg mountains east of Cradock in the Eastern Cape.
These birds, also not connected to each other in any way, have all ended up in almost exactly the same area of about 40km apart, after flying between 700km and 800km.
“And we think they’re going to stay there. Their journey was incredibly straight and I think they’ve been cueing in on the earlier rains there,” says Simmons.
“The grasslands there are lush and green with all the summer rains and it must be a paradise for these birds. But how they know this is the best area to be in, I don’t know.”
UCT001 set something of a flying record during her journey, clocking an incredible 413km during a 10-hour period – the largest single move recorded for a migrating Black Harrier.
When the birds were first fitted with tags, Simmons expected to see them heading north towards the grasslands of southern Namibia.
“But they didn’t; we were shown up – but it’s always more interesting when that happens. And this information (from the tags) is pouring in. Every day I get up and see what they’ve been doing – it’s fun and it’s really exciting!” - Sunday Argus
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