Recovery Plan for the Northern Spotted Owl - DRAFT
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Recovery Plan for the Northern Spotted Owl - DRAFT

Recovery Plan for the Northern Spotted Owl - DRAFT Recovery Plan for the Northern Spotted Owl - DRAFT

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10.07.2015 Views

4. ConclusionOur knowledge of the natural and life history of the northern spotted owl hasgrown tremendously in the past 10 years. Unlike data available on manythreatened and endangered species, we have preliminary information on thedemography of the owls so that initial projections of populations can be made.However, because the bird is long-lived, estimates of vital rates and, therefore,estimates of lambda (a population's finite rate of growth) may change as thepopulations are followed through time. These changes will occur because ofnormal population responses to good and poor environmental conditions aswell as to habitat changes. It is evident that much more needs to be learnedabout the species (and other late seral stage species) to allow us to refinemanagement plans compatible with the ecology of the species. Nevertheless,more is known about this species than about most endangered or threatenedspecies.30

IL.B. Status and Threats1. Habitat StatusThe present range of the northern spotted owl approximates the limits of itshistoric range. The range extends from southwestern British Columbia souththrough the coastal mountains and the Cascade Range of Washington andOregon, and into northwestern California as far south as San Francisco.Although the total area of the subspecies' range has not decreased, its distributionhas changed greatly. The Puget Trough in Washington and lands adjacentto the Willamette Valley in Oregon no longer support populations of owlsbecause of loss of habitat to urban, rural residential, and agricultural development.In southwestern Washington and northwestern Oregon, timber cuttingand wildfires have greatly reduced habitat, and spotted owl populations arevery low at present. In British Columbia, only some 20 pairs are known toexist; much of the owl's range in Canada has been logged, and little matureand old-growth forest remains.Abundance, distribution, and habitat use of the spotted owl vary across theforest zones that occur within its range. Physiographic provinces as describedby Franklin and Dyrness (1973) incorporate the physical and environmentalfactors that shape the landscape of the Pacific Northwest. These physiographicprovinces were modified by Thomas et al. (1990) and, with slight furthermodification, were adopted by the Recovery Team to describe the range of thespotted owl (Figure 2.2).The extent of owl habitat that existed prior to logging is unknown, but by theearly 1980s more than 80 percent of prelogging old-growth had been removed(Booth 1991). Although not all old-growth forests are suitable spotted owlhabitat (e.g. high elevation forests), this great decrease suggests that the 7.6million acres of habitat that remain today represent only a small portion of thearea formerly occupied by' spotted owl habitat (USDA 1991). Suitable habitaton national forests currently is declining about 1 to 2 percent annually.Mulder et al. (1989) projected that almost all suitable spotted owl habitat onlands suited for timber production would be gone in about 60 years on nationalforests and in about 30 years on BLM lands.Remaining suitable owl habitat is not distributed evenly over the range of thespecies. Habitat reduction has been greatest at low elevations and in the CoastRanges of Oregon and Washington, and this reduction is reflected in lowpopulations of spotted owls in those areas. Remaining habitat at higherelevations may be of lower quality than that which historically was present onlow-elevation lands (Thomas et al. 1990). Thus, the approximately 50 percentof remaining spotted owl habitat currently in reserved areas or in areasunsuited for timber production (Table 2.3) may not contribute proportionally toproductivity, because these lands are commonly at higher elevations.Most remaining suitable habitat is found on federal lands. The Forest Scrvicemanages about 74 percent of this habitat, the BLM about 12 percent, and theNational Park Service about 7 percent. In northern California, as much as 40percent of spotted owl habitat may be on private lands, especially along theCoast Range (Gould pers. comm.). In Oregon and Washington, however, morethan 95 percent of the estimated acreage of remaining owl habitat is found onfederally managed lands.3 1

4. ConclusionOur knowledge of <strong>the</strong> natural and life history of <strong>the</strong> nor<strong>the</strong>rn spotted owl hasgrown tremendously in <strong>the</strong> past 10 years. Unlike data available on manythreatened and endangered species, we have preliminary in<strong>for</strong>mation on <strong>the</strong>demography of <strong>the</strong> owls so that initial projections of populations can be made.However, because <strong>the</strong> bird is long-lived, estimates of vital rates and, <strong>the</strong>re<strong>for</strong>e,estimates of lambda (a population's finite rate of growth) may change as <strong>the</strong>populations are followed through time. These changes will occur because ofnormal population responses to good and poor environmental conditions aswell as to habitat changes. It is evident that much more needs to be learnedabout <strong>the</strong> species (and o<strong>the</strong>r late seral stage species) to allow us to refinemanagement plans compatible with <strong>the</strong> ecology of <strong>the</strong> species. Never<strong>the</strong>less,more is known about this species than about most endangered or threatenedspecies.30

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