The Mexican and U.S. governments are combining forces for the first time to try to save a watershed, the Upper San Pedro River Basin in northern Mexico and southwestern Arizona. The area, the last aviary migration zone in the southwestern U.S., is a stopping point each year for 4 million migratory birds, representing 400 bird species. Mexico is establishing a $1.5 million trust and will seek donations from environmental groups to create a protected area around the river, and the U.S. will seek between $12 million and $18 million over the next few years from the federal Land and Water Conservation Fund to purchase land or easement rights for some 7,000 acres.