LOS ANGELES — Audiences anted up for the Warner Bros. caper "Ocean's Thirteen," the third of George Clooney and Brad Pitt's casino-heist romps, which debuted as the top flick with $37.1 million, according to studio estimates Sunday.

Disney's "Pirates of the Caribbean: At World's End," the No. 1 movie the previous two weekends, sank to second-place with $21.3 million, raising its domestic total to $253.6 million.

Sony's "Surf's Up," an animated adventure about surfing penguins featuring the voices of Shia LaBeouf and Jeff Bridges, debuted in fourth-place with $18 million. That was less than half the $41.5 million opening weekend of last fall's animated-penguin hit "Happy Feet."

"Surf's Up" earned good reviews, but audiences may have viewed it as a retread of "Happy Feet," which finished with nearly $200 million domestically and won the Academy Award for best animated feature.

Lionsgate's gory horror sequel "Hostel: Part II," about rich people who pay to kill victims in grisly ways, opened at No. 6 with $8.75 million, less than half the $19.6 million debut of last year's "Hostel."

The newcomers fell well short of the $60.1 million opening of the animated hit "Cars" over the same weekend last year. After a big summer start, Hollywood revenues dipped for the second-straight weekend, with the top-12 movies taking in $133.6 million, down 9 percent from the same weekend last year.

The three blockbusters that debuted in May — "Pirates of the Caribbean," DreamWorks Animation's "Shrek the Third" and Sony's "Spider-Man 3" — all have trailed off with big drops in revenue after huge first weekends.

Estimated ticket sales for Friday through Sunday at U.S. and Canadian theaters:

1. "Ocean's Thirteen," $37.1 million.

2. "Pirates of the Caribbean: At World's End," $21.3 million.

3. "Knocked Up," $20 million.

4. "Surf's Up," $18 million.

5. "Shrek the Third," $15.75 million.

6. "Hostel: Part II," $8.75 million.

7. "Mr. Brooks," $5 million.

8. "Spider-Man 3," $4.4 million.

9. "Waitress," $1.65 million.

10. "Disturbia," $550,000.