The interior of the Nina Mason Pulliam Rio Salado Audubon Center in South Phoenix tends to be filled with people during the evening hours on every third Thursday of month. Why are they here? The answer is twofold: sex and cheap beer. Both enticements are a major part of the monthly Birds 'n' Beer event. Valley residents pack folding chairs inside the main building of the riparian preserve to fill their bellies with brew and their brains with science. It's a hopped-up scientific soiree that gets plenty silly at times, and it benefits the center's educational and wildlife preservation programs. Attendees can snag cans of Four Peaks craft brews Hop Knot IPA and Kilt Lifter for a $2 donation. After an hour-long mixer among the nature displays in the lobby, everyone grabs a seat for an informative — and typically cheeky — lecture from guest speakers and local scientists on any number of topics. Much of the time, the subject pertains to the sex lives and mating habits of such flora and fauna as sea lions, frogs, plants, or pretty much anything else that reproduces, as well as the occasional oration on bird nesting or the flight patter of bats. Needless to say, the brew-infused, often-humorous nature presentations have become incredibly popular with the public, as a diverse crowd of granola-crunching nature lovers, swanky urbanites, bookish geeks, and curious retirees turn out to learn tidbits concerning courting behavior or watch footage of sea life doing what comes naturally. All that's missing is Marvin Gaye crooning "Let's Get It On."