RALEIGH (WTVD) -- The Bluebird population is once again increasing, and one 99-year-old volunteer is part of the reason why."I love to see the birds and flowers." Bill Satterwhite said. "My mother instilled in me the love of nature. I think I've done my part."Done his part is right. Satterwhite has been volunteering at the JC Raulston Arboretum at NC State for 25 years.He started the Bluebird box program there after realizing the Bluebird population was declining."Not too many years ago, they were almost extinct," Satterwhite said. "Without man-made boxes, we would have no bluebirds. Because we don't have any old dead trees anymore."Bluebirds used to use decaying trees for their nesting sites. Conservation groups said urban development and an increase in competition from other birds for nesting locations made it harder for Bluebirds to breed.A cheap and easy way to help the Bluebirds was to put up man-made bird boxesSatterwhite said he has put up around 100 bird boxes all over Wake County in the last few years, and he has no plans to stop anytime soon.