leader Rory McIlroy of Britain seized a two-shot lead with a birdie at the ninth midway through the second round of the Masters at Augusta National Friday. The 21-year-old McIlroy, who shared the first-round lead after firing a bogey-free 65, reclaimed the lead with birdies at the par-five second and par-four fifth and made the turn at 10 under par to boost his lead over South Korean K.J. Choi. The sun played peek-a-boo on an overcast day at Augusta National and players treated the lead like a game of musical chairs before the young Northern Irishman took charge. Choi, who began the day two shots back after his opening 67, leapfrogged late starter McIlroy with three birdies on the front nine, including the par-three fourth and sixth holes. Spain's big-hitting Alvaro Quiros, who shared the first-round lead with McIlroy, and South Korean Yang Yong-eun also reached eight under par before sliding back. Two prominent players were not joining in the fun. Defender Phil Mickelson was treading water, even par through 15 holes to remain two-under for the championship, while Tiger Woods was one over par through three and level par for the tournament, with the cut projected at one over par. Briton Ian Poulter forecast that scoring conditions could grow more difficult as the day wore on. “It is heating up and the greens are going to dry out a little bit I think,” said Briton Ian Poulter, who shot 69 for a one-under-par 143 total. “There are a couple of trickier pin positions today than there was yesterday and it is definitely going to firm up for the guys in the afternoon.” Australian Geoff Ogilvy, the 2007 US Open champion, climbed the leaderboard despite a double-bogey at the second hole to stand six under par through 16 holes. American Fred Couples, the 1992 champion and Augusta National fan favorite, joined the international party on the leaderboard with five birdies to reach six under par before a bogey at the par-three 16th dropped him to 68 for a 139 total. His compatriot Ricky Barnes made three birdies in the first six holes to get to seven under par but was not able to keep up the pace and faded to one-under 71 for his five-under 139. Yang, who mounted a charge with three birdies in a row from the second and added a birdie at the eighth to hit eight under par, straggled in from there for 72 to join the crew at 139. “I thought I was on a roll,” said Yang, who in 2009 became the first Asian to win a major when he outdueled Tiger Woods at the PGA Championship. “I felt good. And then all of a sudden, I don't know why, but my putter started failing me.” Still on the course at five under par were Quiros (through 16 holes) and Americans Rickie Fowler (9) and Matt Kuchar (6).