On it

Joburg’s lush tree canopy provides a haven for the comings and goings of many bird species

THERE is a killer stalking the Melville koppies and it dumped the corpse of its latest victim close to one of the trails that crisscross the nature reserve.

All the killer left was a leg bone and a clue to his victim’s identity.

The clue was a ring that established the victim as a resident of the reserve and it also provided a name.

This victim was a male Swainson’s spurfowl, one of handful ringed in the reserve.

But what of the killer of this chicken-sized bird? The bird-ringers who gathered early last Saturday in the reserve fingered a prime suspect.

The killer was most likely one of the newer immigrants to the reserve, a black sparrowhawk.

Black sparrowhawks and their cousins, the Owambo and the little sparrowhawk, are newbies to the forested expanse that covers Joburg.

Even on Saturday morning a black sparrowhawk could be seen hugging the contours of the koppies, on the hunt.

It avoided the number of mist nets the ringers had set up. These nets are erected on every second Saturday of the month.

Most of the birds that do end up in the nets are smaller species, Cape white eyes, bulbuls and robins. “And lots and lots of mask weavers,” laughs bird-ringer Craig Nattrass.

Bird-ringers have been ringing in the Melville Koppies nature reserve since 1973. The reserve celebrates its 60th anniversary and the ringers are still going strong.

In that time, these citizen scientists have ringed thousands and thousands of birds, and their meticulous records have plotted the ebb and flow of birds in and out of Joburg.

“They used to catch white-backed mousebirds back then, and there are not as many swifts and swallows as there used to be,” says bird-ringer Karen Dixon.

Just what has not been caught can be found in a report compiled by ringer James Mccluskie. He listed several species that haven’t been caught in the past 10 years.

“It is surprising that the barn swallow, the lesser striped swallow, bokmakierie, Cape weaver, blue waxbill and green-winged pytilia have not been caught for a long time,” he writes in his report.

“There are probably many reasons for this, among them the fact that some of the birds are comparatively difficult to net. It also seems possible, if not likely, that there have been some habitat changes that do not suit some of the species.”

About 3km north of Melville Koppies, Geoff Lockwood has been recording the daily comings and goings of bird life at Delta Park for the past 17 years.

Like the bird-ringers in Melville Koppies, he has also noticed how some species have disappeared while others have moved in. He has a theory about this.

“You sometimes find with a nasty drought that bushveld birds will come into Johannesburg,” explains the ornithologist. “It is almost their last grasp for survival.”

In the case of the white-backed mousebird, it was the reverse, says Lockwood.

As Johannesburg became wetter, thanks to Joburgers watering their gardens, the white-backed mousebirds left, seeking out drier habitats.

With Joburg’s well-watered urban forest, other species have become more plentiful. African Olive pigeons moved in, so have increasing numbers of thick-billed weavers.

Just recently another visitor was spotted at Delta Park, and Lockwood wonders if it is the vanguard of a local migration drawn to the attractions of a big city with plenty of water.

In December, he spotted a whiskered tern. He has seen it since.

“If it bumps into another member of its species it might build up a population, otherwise they might just disappear. It is very hard the first time to predict which way it is going to go,” he says.