A study showed the critically endangered monarch butterfly grew its presence in Mexico last year giving a glimmer of hope to researchers who track the fluttering orange and black migrants despite a decades-long population collapse. Last winter, the pockets of Mexican forest where the intrepid insects end up each year saw 35% more butterflies than in 2020, according to the study led by the local office of environmental organization World Wildlife Fund (WWF). https://cbsn.ws/3M1LV0d | CBS Sunday M