GRAND RAPIDS, 24 July 2015, (AFP) - The 33-year-old Aussie is tied with Americans Dori Carter and Lizette Salas as all three took advantage of the calmer conditions that greeted the morning starters to post low scores at the Blythefield Country Club course in the US state of Michigan.
"I drove it pretty well and I think I hit 16 greens and made quite a few birdies and an eagle," said Kirk, who is seeking her third win on the US Tour.
"So I got off to a good start and kind of just kept it going, which was nice."
Jaye Marie Green and Taiwanese rookie Hsu Wei-Ling were tied behind the leaders at 65 after the first 18 holes of the $2 million LPGA Tour event.
The group at 66 included Kris Tamulis, Baek Kyu-Jung, Ilhee Lee and Jane Rah.
Kirk was red-hot right from the beginning as she started on the back nine. The Brisbane native was four-under through the first four holes which included an eagle on the par-five 11th.
After a bogey on 15, Kirk fashioned back-to-back birdies on 16 and 17.
Kirk, who finished second at the 2010 Women's British Open, made a birdie at the first. After rattling off three consecutive pars she drained her sixth birdie of the round at the fifth.
She then went par-bogey before capping her round with another birdie at the ninth.
Carter posted eight birdies, including three in a row on numbers four through six.
The best part of Salas' bogey-free round was an eagle at the par-five 11th hole to go along with five birdies.
"It felt good, to end on a note like that is really positive," said Salas of her consecutive birdies to finish her round.
"I plan to just kind of go out on the practice area today, focus on the greens and really try to keep it going the next three days."
Hsu was among the players with afternoon tee times who had to deal with more wind.
Top-ranked Inbee Park was part of a large contingent tied for 37th after opening with a 70.
The 2014 tournament runner-up got off to a slow start in the first round with three bogeys on the front nine. Park lost in a playoff to Lee Mi-Rim last year.
Chella Choi, who won the Marathon Classic last weekend in Ohio, shot an even-par 71.
Leading first-round scores on Thursday from the LPGA Tour's Meijer Classic (USA unless noted, par-71):
64 - Katherine Kirk (AUS), Dori Carter, Lizette Salas
65 - Jaye Marie Green, Hsu Wei-Ling (TPE)
66 - Kris Tamulis, Jane Rah, Ilhee Lee (KOR), Baek Kyu-Jung
67 - Sarah Kemp (AUS), Alison Lee
68 - Pat Hurst, Alena Sharp (CAN), Sarah Jane Smith, Belen Mozo (ESP), Oh Ji-Young (KOR), Sandra Changkija, Katy Harris, Amy Anderson, Laetitia Beck (ISR), Brooke Pancake, Kim Kaufman