>> finally tonight, big rebound after years of decline, monarch butterflies are back in big numbers. cbs's carter evans explains why. >> at the crack of dawn the golfers here are not alone. >> you want to count in groups of five or ten. >> researcher richard rachman is also on the green counting monarch butterflies just hanging out behind the 9th hole. >> is this pretty typical. >> absolutely. here we have a few hundred that are clustering close together. they just look like pinecones or dead leaves, most people walking by would never even see them. >> an estimated 200,000 migrating western monarchs are spending the winter here in california. last year only 2000 were spotted. and they were thought to it be on the verge of extinction. >> some of the biggest factors that are impacting monarch populations are insecticides used in agriculture and habitat loss. as more people are moving out