In good weather, the bees can begin to bring nectar and pollen to the hive from early blooms. Strong, successful hives may begin to think about swarming late in the month. Pick a nice sunny day to perform a thorough inspection for eggs, brood pattern, disease, and stores.
John talked about March tasks in the bee hive, and showed pictures of different brood patterns in his Bees on the March presentation at our March 2015 meeting.
The Oregon State Beekeepers Association website has a lot of information about mite treatment approaches in March in their February and March section.