Status of the peregrine falcon in the Rocky Mountains and the southwestern United States, Baja California, and Mexico (south of Texas)

Abstract

About 31 pairs of peregrines still nest north of Mexico, from Idaho and Montana south through West Texas, New Mexico and Arizona. At least thirty-six additional pairs nest in Mexico. Although the nesting sites are occupied, the tissues of the peregrine?s prey species still contain high concentrations of pesticides. The eggs in some Rocky Mountain eyries have shells which are precariously thin and have high residue levels of DDE in their contents. Increasing economic development is encroaching on the peregrine habitat throughout its range in western North America. In Baja California. and Mexico south of Texas this involves increased agricultural activity including use of organochlorine pesticides, increased tourism and increased use of the Gulf of California both for commercial and sport fishing, with their potential disturbance of eyrie sites and reduction of the peregrine?s aquatic feeding prey base. As the fish in the Gulf decrease in number, some of the avian species on which peregrines prey will likewise decrease. This ultimately may effect the peregrine. These factors may have been involved in the demise of the peregrine on Baja California?s Pacific coast. Furthermore, throughout its range, residential, industrial, mining, geothermal, recreational and other types of development and land use practices sometimes destroy habitat essential to the survival of the peregrine. A recent request for the protection of an historical site in California as Critical Habitat under Section 7 of the Endangered Species Act was rejected because peregrines, although observed there, were not known to have produced eggs or young at the site for several decades. With inadequate protection of abandoned, but still suitable, historical eyrie sites, the peregrine may have an insufficient number of eyries to reoccupy in recovery attempts. The lack of present occupancy of a site, without biological evidence that the site is no longer suitable for reoccupancy, is insufficient cause to give up the site to the pressures of development. Since destruction of habitat is forever, preservation of this essential habitat is of utmost importance to the survival of the species. On the other hand, we must not allow the peregrine, or other of the endangered species, to be used as levers for the sole purpose of restricting economic development. When an impasse between the two does occur, our defense of the endangered species must be justified on sound biological evidence if the Endangered Species Act of 1973 is to survive. The formation of the recovery teams, the development of recovery plans, and the success of captive breeding and reintroduction projects are all on the plus side of the ledger for the peregrine. They suggest optimism for the future of the peregrine, providing use of DDT is restricted both north and south of our southern border, and a sufficient number of the still suitable inactive eyrie sites are preserved to effect recovery. We need to categorize all active and inactive sites on the basis of quality and/or suitability for reoccupancy and preserve those required for the recovery of the species. Categorizing inactive eyries as to suitability for reoccupancy will provide land management agencies information badly needed for critical value judgements affecting the future of the peregrine falcon in the West.