South African John Bland and Englands Denis Durnian each opened in 3-under-par 68 at Royal County Down Golf Club to earn the Day 1 lead.
Bland has posted three runner-up finishes in this event over the past four years. Hes finished second to Christy OConnor, Jr. twice (1999 and 2000); however, OConnor is not in attendance after breaking his foot when his motorcycle fell on him earlier this year.
The 55-year-old made the turn in 4-under 31 after making an eagle at the par-5 first and birdies at the 7th and 9th holes. His only dropped shot of the day came on the final hole.
Nicklaus, 61, also started the championship with an eagle at the First and then recorded birdies on the par-5 12th and par-4 16th.
I suppose a 70 on the board is a pretty good score but I think I probably played a little bit better than that, said Nicklaus, who won three Open Championships while on the regular tour.
I had good chances on quite a few of the holes on the front nine but I didnt make the putts. But I cant complain. When I walk home tonight and see 70 on the board in the first round of your Open I am sure I will think its not a bad score.
Nicklaus had a chance to end a five-year winless drought in the U.S. Senior Open. But, tied for the lead at even par, he tried to hit a 1-iron onto the green at the par-3 15th. He failed to do so and made bogey. Nicklaus added another bogey at the No. 16 to finish the tournament at 2-over and in a tie for fourth.
Two weeks ago, Nicklaus was forced to withdraw from the Ford Senior Players Championship due to an injured hamstring, which he said has not fully healed.
Durnian, who won the 2001 Wales Senior Open, is one of the top players on the European Seniors Tour. Two-over through five holes, he birdied the 7th, 10th, 11th, 16th and 18th holes.
Brian Huggett of Wales, New Zealands Bob Charles, Japans Noboru Sugai, Englands John Morgan and Scotsman Bernard Gallacher are all tied for third after shooting 2-under-par 69s.
Full-field scores from the Senior British Open