Australia’s Jason Day surged to the top of the leaderboard midway through the first round at the PGA tour event at Torrey Pines following a run of four successive birdies.

Day, the world No.10, had started on the back nine on the north course and birdied the 15th hole before his fantastic run started at the 18th.

A birdie there was followed by another at the first, Day taking advantage of the two par fives before continuing his push at the second and third.

Par at the par-four fourth stopped his run and he was joined on five under through 13 by Stewart Cink, who birdied the first, second, fourth, 11th and 13th.

Englishmen David Lynn and Greg Owen and European Ryder Cup star Nicolas Colsaerts were among an extensive group at three under, which also included major winners Bubba Watson and Keegan Bradley.

Americans Charley Hoffman and Pat Perez were the only players on the south course among that group.

Phil Mickelson was among the group at two under, with rising star Jordan Spieth a further shot back.

Tiger Woods joined Bill Haas in the bunch at level par, Lee Westwood was one over along with Brandt Snedeker and Ian Poulter was struggling at three over.