UPHILL BATTLE:

Mountain bikers with racing on their minds have three classes to choose from in Saturday's Whiskey Ridge Races in Sharpsburg, Md. -- novice, sport/vet and expert. Racing starts at 9:30 a.m. Entry fee is $15. Call (301) 582-4747.

Maryland's Mountain Bike Championship will follow the next weekend, Oct. 27-28, at Green Ridge State Forest in Allegany County. Call (301) 777-2345.

RING OF THE RISE:

Potomac-Patuxent Chapter of Trout Unlimited hears from Bob Gartner on fishing in national parks at its regular meeting at 7:30 Thursday at Glenallan Elementary School, 125 Heurich Rd., Silver Spring. The public is welcome. Call (301) 384-0424.

ALOHA:

Audubon Naturalist Society presents a talk on saving Hawaii's forest birds at 1 p.m. today at Woodend, the society's 40-acre preserve at 8940 Jones Mill Rd., Chevy Chase. The talk by Jeff Hatfield is in conjunction with a show of Hawaiian wildlife art that will run through Oct. 30. Call (301) 652-5964 for reservations.

WATERFOWL:

Potomac Valley chapter of Ducks Unlimited will have its annual dinner and auction Oct. 24 at the Sheraton Premier Hotel in Tysons Corner. Ticket price of $75 includes a one-year membership in DU. Call Dwight Lee, (703) 690-2166, or Bob Johnston, (703) 442-8990.

RIVER RATS:

Fans of the Patuxent, Maryland's longest intrastate river, will head to Solomons Island today for the last of Patuxent River Appreciation Days. Oysters, clams and crabs should be plentiful, plus educational, environmental and cultural exhibits at Calvert Marine Museum and free boat rides on the Miss Solomons and the Gator. Call (301) 333-6611.

SHOWTIME:

The U.S. Powerboat Show, with more than 600 boats, including 350 in the water, winds up today at Annapolis City Dock. Queen of the fleet is the 84-foot Altech Motor Yacht. Admission is $8, $4 for children 12 and under. Hours are 10-6. Call (301) 268-8828.