You know it’s August when two major studios agree to share the weekend B.O. title.

Sony and Warners reached a detente, with “Hollow Man” and “Space Cowboys” each fetching an estimated $13.1 million in their second frames. Both prevailed over a trio of debuts, Warners’ “The Replacements,” MGM’s “Autumn in New York” and Paramount’s “Bless the Child.”

Co-champs led a field that saw the top seven pics bunched between $9.6 million and $13.1 million. The slate may be crowded, but in terms of commercial and critical impact, it’s about as fascinating as a public-radio pledge drive.

Not only is $13.1 million the lowest No. 1 tally since April, but it’s the first time since “Mission: Impossible 2” repeated atop the chart in June that a sophomore has claimed the crown.

Summer receipts have slipped about 4% behind last year’s record pace. At about $105 million, as estimated by ACNielsen EDI, the weekend gate dropped 19% from last year’s robust total of $129.4 million. Year-to-date grosses entered the frame 3% ahead of 1999, but by the end of August that lead should be gone.

“Business is strong,” said ACNielsen EDI prexy Tom Borys, noting the comparable 1998 weekend came in at $103 million. “It’s just not record-setting.”

Unlike most neck-and-neck weekends, when studios toot their own horns and blast the competish, Sony and Warners broke bread and focused on the staying power of their pics. Warners was especially cheered by “Cowboys,” whose 28% drop was the slimmest of any top pic and one of the best holds of the summer.

“From the exit polls we’ve had, it’s obvious that people have enjoyed this movie,” WB distrib chief Dan Fellman said. “When Clint Eastwood gets in a good movie and people discover it, it just keeps playing. I think this one is going to continue to put up some big numbers.”

Sony distrib prexy Jeff Blake also likes the long-term prospects for “Hollow,” despite an above-average decline of 50% in Week 2.

“I still think we’re in good shape,” he said of the thriller that cost at least $90 million to produce. “We’re probably headed toward $85 million to $90 million domestically. We’re hoping to hold in through Labor Day.”

Thriving until September will be a feat indeed for “Autumn in New York,” but its launch is a success for MGM, whose last release was “Return to Me” in April. It’s the third best bow for both of its stars, Richard Gere and Winona Ryder.

It vindicates the studio’s smirk-inducing decision not to screen the pic for critics, often a sign of damaged goods.

Having spent a modest $14 million for domestic rights to the Lakeshore-produced pic, the Lion didn’t have a great deal at stake. But officials said their marketing strategy sought to minimize awareness of a central story element: that Ryder’s character has a terminal illness that’s revealed in Act One.

Exit polls showed the impact of such a downbeat arc: a below-average 50% of auds listed the pic as a “definite recommend.” Also, crowds were heavily skewed at 70% female and 60% over 25.

“Even if it doesn’t have the greatest playability, we think it can continue to draw adult women,” said Larry Gleason, head of distribution for MGM.

Keanu Reeves starrer “The Replacements” had the most crowd-pleasing buzz of any of the weekend’s top pics, but it didn’t translate into dollars for Warners’ football comedy. Reviews were fairly generous, and aside from Reeves in his first post- “Matrix” role, pic also stars Gene Hackman, Jon Favreau and “Notting Hill’s” Rhys Ifans.

Lower star wattage from Kim Basinger and Jimmy Smits may have hampered Par’s R-rated “Bless the Child.” Blessed with a fairly assertive marketing push, supernatural thriller managed a No. 7 showing, behind well-established genre competitor “What Lies Beneath” from DreamWorks. Harrison Ford-Michelle Pfeiffer chiller improved its retention from last week, dropping just 29% and bringing its total to $112.1 million.

Elsewhere on the big board, a 55% dive for “Coyote Ugly” must have had some Disneyites howling at the moon. Cume of $34.2 is comely, but weekday results suggested a better hold for the Jerry Bruckheimer production.

Two entrenched titles neared milestones during the frame. Universal’s “Nutty Professor II: The Klumps” put up another $10.3 million and should cross $100 million by next weekend. DreamWorks’ “Chicken Run” will hit that charmed gross level today and is on track to become the studio’s most successful animated effort.

For the second straight week, the specialized scene boasted some of the industry’s most dynamic titles.

Fine Line’s “Saving Grace” bucked the usual attrition trend and actually increased its grosses at many sites. Marijuana pic boasts exceptional weed-of-mouth — exit polls are stronger than Fine Line’s pride and joy, the $36 million-grossing “Shine.” Comedy collected $358,000 from 35 sites, five more than last week.

At an average of $10,229 per location and a 10-day cume estimated at $788,000, art arm of New Line hopes to expand “Grace” to 250 locations on Friday, about 100 more than previously planned. Fine Line also debuted “An Affair of Love” and recorded $27,300 on four screens — about $18,000 of which came from Gotham’s Lincoln Plaza.

Artisan notched one of the summer’s top indie openings with “Cecil B. Demented.” John Waters-helmed pic grossed $130,000 on nine screens, for a stellar average of $14,444.

Shooting Gallery’s “Croupier” added $210,000 on 127 screens to bring its cume to $4.4 million.

Paramount Classics’ “Sunshine” cleared the $5 million barrier with a $225,000 weekend. Ralph Fiennes starrer has joined the elite handful of 2000 pics to strike gold below 500 runs.