Section 9 of the Endangered Species Act (ESA) makes it unlawful for any person to "take" an endangered or threatened species of fish or wildlife. A definition section in the ESA states that take means "to harass, harm, pursue, hunt, school, wound, kill, trap, capture, or collect, or to attempt to engage in any such conduct." The Secretary of the Department of the Interior (the Secretary) promulgated a regulation that defined the term harm for purposes of the statutory language just quoted. This regulation stated that harm "means an act which actually kills or injures wildlife" and that "such act may include significant habitat modification or degradation where it actually kills or injures wildlife by significantly impairing essential behavioral patterns, including breeding, feeding or sheltering." A declaratory judgment action attacking the validity of this regulation was brought against the Secretary by a group of landowners, logging companies, and families dependent on the forest products industries, and by organizations representing those parties' interests. The plaintiffs sought a judicial ruling that the regulation defining harm as including habitat modification or degradation was an unreasonable and erroneous interpretation of the ESA. The plaintiffs alleged that they had been injured economically by the government's application of the harm regulation to the redcockaded woodpecker, an endangered species, and the northern spotted owl, a threatened species. Was the Department of the Interior's regulation a reasonable interpretation of the statute?