Recovery Plan for the Northern Spotted Owl - DRAFT
Recovery Plan for the Northern Spotted Owl - DRAFT Recovery Plan for the Northern Spotted Owl - DRAFT
predict the power achieved by different designs given numbers recorded perstation, number of stations per year, and so on. The new programs wouldbe similar, but would include the benefits gained from stratification anddouble-sampling.4. What "domains" to obtain estimates for?The term domain refers to a portion of a sampled population about whichinferences are desired. A domain might consist of a certain province, DCAsof a certain type, or a certain environment. Domains may be redefined indifferent analyses; they do not all have to be identified before the analysesare conducted, and in reality, new domains are nearly always defined as theanalysis proceeds. Much of the "art" in sampling involves trying to maximizethe number of new domains of interest that can be constructed andstudied after the data have been collected. The process, however, obviouslyis easier if the domains are specified during design of the sampling program.For spotted owls, domains of interest include provinces, states, DCAs,federal land outside of DCAs, and several different environments. Thetentative list of domains to be studied in the monitoring program should bedeveloped and used in making final sample size decisions.Activity site monitoringFor this sampling program, the owl's range (including the demographic areas)would be subdivided into strata as in the roadside survey program. The stratacould be different but there might be considerable advantage to having thesame strata in the two programs. The sample size within each stratum wouldbe determined, and areas would be chosen randomly (except for "censused"strata). The selected areas would be surveyed to identify all activity sites, andone or more sites would be selected randomly. These sites would be surveyedfor some minimum number of years. Surveys would be conducted according toan approved protocol and the birds present at each site in each year would bebanded so that turnovers could be identified. Productivity (number of fledglingsproduced) would be recorded, as would age of first-time territory holdersand replacement times. Habitat information also should be collected about theactivity site and surrounding area.The major tasks needed for initiation and refinement of this program includethe following:1. Decide on stratification procedure and sample size requirements.Most of the comments made earlier about designing the roadside surveysapply to this program as well. Existing data on productivity, turnover rate,age ratios, and replacement times should be studied to obtain advanceestimates of the parameter values and the covariance structure of the data.The possibility of roadside bias should be investigated. Domains of interestshould be identified in advance, as much as possible, and the design shouldstrive to accommodate the new domains that undoubtedly will be identifiedafter analysis begins. Domains for the activity site monitoring may bedefined using either landscape features or features of the habitat in theimmediate vicinity of the activity site.2. Develop a program for recording habitat information about the activity site.Standardized methods should be developed for collecting data on the habitatat the nest site and in the nearby areas. This work will involve decidingwhat areas around each site should be characterized, and what informationshould be collected. The information should serve the purposes of biologists272
studying how demographic rates vary in different habitats and ofsilviculturalists studying ways to develop or maintain suitable habitat.Consideration should also be given to collecting information about habitatfor other species.3. Ensure that potential participants in the program have an opportunity tolearn capture and banding techniques and obtain required permits.Training programs and assistance in obtaining required permits should beprovided for potential participants in the program.Transmitter studiesAs noted earlier, studies are needed of dispersing juveniles and territorial andnonterritorial adults. The information provided by the studies will be useful indemographic analyses, populations projections, and in the efforts to modelpopulation dynamics, and in the 'other methods" described earlier. Thefollowing investigations are particularly important.1. Estimate juvenile survival and investigate the factors that affect it.As described in the section on demographic rates, biased estimates ofjuvenile survivorship, caused by emigration or nonterritorial status, areamong the most troublesome problems in the estimation of trends based ondemographic analyses. New, lightweight transmitters appear to offer thepotential for estimating juvenile survival rates by following individuals birds(rather than via capture-recapture studies). One major study using thisapproach is underway in the Olympic Peninsula, and other similar effortswould be valuable.2. Estimate natal dispersal distances and the factors affecting them.Natal dispersal distances, the straight-line distance between the birthplaceand area of permanent settlement, provide a second way to evaluate thedemographic estimates (by permitting an estimate of emigration rates), andwill be of great help in evaluating the recommended DCA system. Dispersaldistances of more than 100 juvenile spotted owls that survived to becometerritorial adults were collected recently. Study of this data set will aid ourunderstanding of dispersal.3. Evaluate and improve the definition of 'dispersal habitat."The 50-11-40 rule is currently being used to define dispersal habitat, butbiologists agree that more information is needed about dispersal habitat.The 50-11-40 rule probably applies better in some parts of the range than inothers, other values for the three parameters might provide suitable dispersalhabitat thereby giving managers a range of alternatives, and anentirely different definition of dispersal habitat (e.g., amount of old-growthremaining in the landscape) might be useful and appropriate in some cases.Understanding the requirements for successful dispersal probably willrequire intensive monitoring to determine what habitats are used, and forwhat purposes, by dispersing juveniles.4. Study movements and behavior of floaters.This issue is critical in modeling population dynamics and in using thechange in age ratio of first-time breeders as an early warning of imminentpopulation decline. Perhaps the biggest obstacle in these studies is developingways to capture nonterritorial birds so that transmitters can be at-273
- Page 238 and 239: and the number of invertebrate anim
- Page 240 and 241: Table 5.2. Numbers of other species
- Page 242 and 243: Amphibians and Reptiles: Larch Moun
- Page 244 and 245: 228
- Page 246 and 247: 230
- Page 248 and 249: Barrows, C. W. 1980. Feeding ecolog
- Page 250 and 251: Clark, R. J., D. G. Smith, and L. H
- Page 252 and 253: Franklin, A. B., J. A. Blakesley, a
- Page 254 and 255: Harestad, A. S., and F. L. Bunnell.
- Page 256 and 257: Lundquist, R. W. and J. M. Mariani.
- Page 258 and 259: O'Halloran, K. 1989. Spotted owl in
- Page 260 and 261: Solis, D. M. 1980. Habitat use by n
- Page 262 and 263: Young, K. D., A. B. Franklin, and J
- Page 264 and 265: 248
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- Page 268 and 269: Table A.1. General approaches for e
- Page 270 and 271: complete count of the territorial b
- Page 272 and 273: Table A.3. Powera for various desig
- Page 274 and 275: Table A.4. Illustration of a Markov
- Page 276 and 277: Obviously, these statements hold on
- Page 278 and 279: Table A.6. Reliability of trend est
- Page 280 and 281: Demographic AnalysisAs noted earlie
- Page 282 and 283: the estimate (using the simple equa
- Page 284 and 285: however, we know little about the b
- Page 286 and 287: Table A.8. Summary of information n
- Page 290 and 291: Other studiestached. If dispersing
- Page 292 and 293: impractical at present. We describe
- Page 294 and 295: Conclusionsthe year effect can be i
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- Page 302 and 303: owls. Consequently, the issue of wh
- Page 304 and 305: Use of the informationAssessments a
- Page 306 and 307: Recent LiteratureWe might begin by
- Page 308 and 309: Kerms (1989) measured habitat struc
- Page 310 and 311: Hamer (pers. comm.) described 11 ne
- Page 312 and 313: Table B.3. Percent hardwoods in the
- Page 314 and 315: Table B.5. Comparison of habitats u
- Page 316 and 317: Table B.8. Tree density (number of
- Page 318 and 319: and numbers of trees, and percent o
- Page 320 and 321: Under this hypothesis, owl fitness
- Page 322 and 323: suitable habitat for that region (m
- Page 324 and 325: ResultsDiscussionspotted owl habita
- Page 326 and 327: __Discussiondata from 41 sites in t
- Page 328 and 329: Recommendations for Future Research
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- Page 332 and 333: Hamer, T. 1988. Home range size of
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studying how demographic rates vary in different habitats and ofsilviculturalists studying ways to develop or maintain suitable habitat.Consideration should also be given to collecting in<strong>for</strong>mation about habitat<strong>for</strong> o<strong>the</strong>r species.3. Ensure that potential participants in <strong>the</strong> program have an opportunity tolearn capture and banding techniques and obtain required permits.Training programs and assistance in obtaining required permits should beprovided <strong>for</strong> potential participants in <strong>the</strong> program.Transmitter studiesAs noted earlier, studies are needed of dispersing juveniles and territorial andnonterritorial adults. The in<strong>for</strong>mation provided by <strong>the</strong> studies will be useful indemographic analyses, populations projections, and in <strong>the</strong> ef<strong>for</strong>ts to modelpopulation dynamics, and in <strong>the</strong> 'o<strong>the</strong>r methods" described earlier. Thefollowing investigations are particularly important.1. Estimate juvenile survival and investigate <strong>the</strong> factors that affect it.As described in <strong>the</strong> section on demographic rates, biased estimates ofjuvenile survivorship, caused by emigration or nonterritorial status, areamong <strong>the</strong> most troublesome problems in <strong>the</strong> estimation of trends based ondemographic analyses. New, lightweight transmitters appear to offer <strong>the</strong>potential <strong>for</strong> estimating juvenile survival rates by following individuals birds(ra<strong>the</strong>r than via capture-recapture studies). One major study using thisapproach is underway in <strong>the</strong> Olympic Peninsula, and o<strong>the</strong>r similar ef<strong>for</strong>tswould be valuable.2. Estimate natal dispersal distances and <strong>the</strong> factors affecting <strong>the</strong>m.Natal dispersal distances, <strong>the</strong> straight-line distance between <strong>the</strong> birthplaceand area of permanent settlement, provide a second way to evaluate <strong>the</strong>demographic estimates (by permitting an estimate of emigration rates), andwill be of great help in evaluating <strong>the</strong> recommended DCA system. Dispersaldistances of more than 100 juvenile spotted owls that survived to becometerritorial adults were collected recently. Study of this data set will aid ourunderstanding of dispersal.3. Evaluate and improve <strong>the</strong> definition of 'dispersal habitat."The 50-11-40 rule is currently being used to define dispersal habitat, butbiologists agree that more in<strong>for</strong>mation is needed about dispersal habitat.The 50-11-40 rule probably applies better in some parts of <strong>the</strong> range than ino<strong>the</strong>rs, o<strong>the</strong>r values <strong>for</strong> <strong>the</strong> three parameters might provide suitable dispersalhabitat <strong>the</strong>reby giving managers a range of alternatives, and anentirely different definition of dispersal habitat (e.g., amount of old-growthremaining in <strong>the</strong> landscape) might be useful and appropriate in some cases.Understanding <strong>the</strong> requirements <strong>for</strong> successful dispersal probably willrequire intensive monitoring to determine what habitats are used, and <strong>for</strong>what purposes, by dispersing juveniles.4. Study movements and behavior of floaters.This issue is critical in modeling population dynamics and in using <strong>the</strong>change in age ratio of first-time breeders as an early warning of imminentpopulation decline. Perhaps <strong>the</strong> biggest obstacle in <strong>the</strong>se studies is developingways to capture nonterritorial birds so that transmitters can be at-273
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