LINN COUNTY — It didn’t take long for a pair of sandhill cranes to prove the adage, ‘If you build it, they will come.’A wetland built last winter at Linn County’s Matsell Bridge Natural Area is home this spring to the county’s first documented successfully reproducing sandhills of the modern era.“This is awesome, unbelievable, really cool,” said natural resources specialist Dana Kellogg, who coordinated the wetland construction.Linn County officials noticed a pair of sandhills in the wetland this spring.