Up to 10 species of hummingbirds use the green corridor of the San Pedro River as a freeway between their tropical winter retreats and their northern nesting grounds. The public is invited to get a close-up look at these tiny travelers as staff and volunteers from the Southeastern Arizona Bird Observatory capture, band, weigh, measure, and release them as part of long-term studies of the bird life of this vital migration route.  Donations are gratefully accepted.  For more information contact the Southeastern Arizona Bird Observatory at (520) 432-1388 or visit www.sabo.org.