Kavanagh had four birdies and one bogey at the Royal Durban Golf Course.
The course and the wind were both difficult, Kavanagh said. To play in the Open will be really special. Im not getting ahead of myself, but if it happens that I get through the qualification, it will be fantastic.
Da Silva opened with birdies on the first two holes.
Darren Fichardt of South Africa, who won on the Sunshine Tour last weekend, was a stroke behind, while Tyrone Ferreira, Henk Alberts, Tyrone van Aswegen and Marc Cayeux were a further shot back.