In 1997, when the US Fish and Wildlife Service listed the Pygmy-Owl as endangered under the Endangered Species Act, we had little biological information available to guide the debate. Efforts to survey large portions of southern Arizona began soon after in 1998 and 1999. We soon discovered that Pygmy-Owls were rare and that most occupied sites were in xeroriparian woodlands and adjacent desert scrub and grassland with saguaros, as well as in native and exotic vegetation on the outskirts of northwest Tucson. However, we found very few Pygmy-Owls along major river valleys where they were described as common in the early 1900s, probably due to the loss of large riparian forests. By 2000, there was still little information on the status of Pygmy-Owls in adjacent Mexico and on important habitat attributes.