Updated

Vilamoura, Portugal (SportsNetwork.com) - Jamie Donaldson carded a 6-under 65 on Thursday to grab a share of the lead after the opening round of the Portugal Masters.

Donaldson, the fourth-highest ranked player in the field at world No. 44, was joined atop the leaderboard by David Lynn, 2008 champion Alvaro Quiros, Graeme Storm, Felipe Aguilar, Simon Thornton and Maximilian Kieffer.

Bernd Wiesberger, who finished fourth at this event last year, opened with a 5-under 66. He shares eighth place at Oceanico Victoria Golf Club with Soren Hansen, Hennie Otto, Marcel Siem, Julien Quesne, Chris Wood, Scott Jamieson, Mark Tullo and Andy Sullivan.

Ross Fisher is among 13 players tied for 17th at minus-4.

Donaldson started on the back nine and ran off three straight birdies from the 12th. He birdied the 17th to make the turn at minus-4.

After three pars in a row from the 18th, the Welshman poured in three birdies in a 4-hole span from the third to jump to 7-under. He was in the lead at that point, but stumbled to a 3-putt bogey on the eighth to fall back to minus-6.

Lynn and Quiros were in the group behind Donaldson. Lynn started with three birdies in the first four holes. He traded a birdie for a bogey from the 17th.

The 39-year-old Englishman had six pars and a birdie in the first seven holes around the turn. He closed his round with birdies on the eighth and ninth.

Quiros, who topped Paul Lawrie for the 2008 title, stumbled to bogeys at 12 and 14, but came back with birdies at 15 and 17 to make the turn at even-par.

On the front side, the Spaniard birdied five of the first six holes, including four in a row from the third, to get within one of the lead. Quiros birdied the ninth, his last, to grab a piece of the lead.

"It was a good fight after being two-over after five holes. I was putting beautifully and that was the key," Quiros said. "This is my second home tournament and now that I'm living here I have to consider Portugal home. It's always good, this event has been special since I've been coming here."

Kieffer was in the third-to-last group out off the 10th. He eagled the 12th and parred the other eight holes of his opening nine. After consecutive birdies at one and two, he birdied the fifth and ninth to close out a bogey- free round.

Thornton birdied the fifth and eighth, but dropped a shot on nine to turn in minus-1. He ran off four consecutive birdies from the 12th, then birdied the 18th for his share of the lead.

"I played lovely, it's always nice to get off to a good start. I hit it straight off the tee and had lots of chances," Thornton stated. "Over the past couple of weeks, I've been playing much more consistently."

Aguilar played the front nine in even-par with two birdies and two bogeys. He drained three straight birdies from the 10th and again from the 15th to shoot 65.

NOTES: Defending champion Shane Lowry posted a 1-under 70 and is tied for 52nd ... Former champions Tom Lewis and Steve Webster are also tied for 52nd at minus-1, while 2010 winner Richard Green is one back at even-par.