Andrade, of Bristol, R.I., shot one of two bogey-free rounds on Thursday, with the other turned in by Wes Short Jr., of Austin, Texas, who opened with a four-under 66 and is alone in third place. Andrade, whose best finish in six previous US Senior Open starts is a tie for sixth in 2015 at Del Paso Country Club in Sacramento, Calif., birdied all three par-5 holes in his afternoon round on the hilly Omaha layout and birdied Nos. 16 and 17 to earn a share of the lead with Ames, who had played in the morning.

“It was kind of stress-free,” said Andrade, who won four times on the PGA Tour and has three victories on the PGA Tour Champions. “I hit the ball fairly solid today, kept it in play, didn’t have too many hiccups, didn’t miss too many fairways. Overall ecstatic with my start.”

Ames, a native of Trinidad and Tobago who has lived in Vancouver, British Columbia, since 2005, has a pair of top-10s in five previous US Senior Open starts. His best showing is a tie for sixth in 2019 on the Warren Course at the University of Notre Dame, the last time the championship was played. The 2020 championship was canceled due to COVID-19.

“Like a lot of players have noticed, it’s an endurance test this week with all the hills,” said Ames of the Perry Maxwell-designed Omaha course, which hosted the 2013 US Senior Open, won by Kenny Perry. “So we decided to take it very easy this week, and luckily for us, a cold front has come through. It was very pleasant this morning and a lot of fun to play.”

“It was kind of stress-free. I hit the ball fairly solid today, kept it in play, didn’t have too many hiccups, didn’t miss too many fairways. Overall ecstatic with my start." – Billy Andrade

Alex Cejka, a native of the Czech Republic who now lives in Germany, and Robert Karlsson of Sweden, both competing in their first US Senior Open, opened with rounds of three-under 67 to share fourth place. Cejka, who turned 50 in December, is seeking his third senior major title of 2021, having captured the Regions Tradition and the Senior PGA three weeks apart in May. Only Jack Nicklaus (1991) and Bernhard Langer (2017) have won three senior major titles in a single season.

Miguel Angel Jimenez, of Spain, a two-time runner-up in five starts in this championship, and Fran Quinn, of Holden, Mass., are tied for sixth place after rounds of two-under 70.

Two-time US Open champion Lee Janzen, 1992 Masters winner Fred Couples, 2014 US Senior Open champion Colin Montgomerie and Jay Haas, at 67 the oldest player in the field, highlight a group of eight players tied at one-under 69.

Eleven players – including major champions David Toms, Tom Lehman, Mike Weir and Mark O’Meara, as well as amateurs Jeff Wilson and William Mitchell – finished at even-par 70.

Jim Furyk, the 2003 US Open champion, shot two-over 72 on Thursday in his US Senior Open debut, while four-time major champion Ernie Els shot a three-over 73 in his first Senior Open round.