Today Oktoberfest at Thompson Park: 11 a.m. Saturday, Thompson Park, 420 Bross St., Longmont. Longmont Humane Society presents Oktoberfest, complete with beer and pretzels, but also including a variety of live music and food and beverage selections for all tastes. There will be lots of fun and games as well as a local artisan market to get ahead on holiday shopping. $15-$75, business.longmontchamber.org. Guided Bird Walk: 8 a.m. Saturday, Old St…