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Flammulated, Boreal, and Great Gray Owls in The Chapter 12 Information Needs: Boreal Owls Gregory D. Hayward, USDA Forest Service, Rocky Mountain Forest and Range Experiment Station, Laramie, WY 82070 INTRODUCTION servation strategies. In the western United States (excluding Alaska), our knowledge is sufficient to Most humans are reluctant to make decisions with- predict, on a broad scale, where boreal owls are likely out thorough knowledge of the consequences of to occur and thereby indicate to land managers those decisions. Therefore, a desire for further re- where management of the species should be a con- search is almost universal in any complex manage- cern (see Map 2). In Alaska and east of the Rocky ment arena. The value of further study is deter- Mountains, particularly in the Great Lakes region mined, in part, by the cost in time and resources to and New England, understanding of the species dis- obtain new information and the cost of making in- tributional status is very weak. Knowledge of dis- correct decisions without the desired knowledge. In tribution is growing rapidly, however, and land the case of managing forest lands and conserving management agencies have the capability to obtain boreal owls, our knowledge is so limited that well the necessary information in several years. Methods directed research on distribution, habitat use at many for determining boreal owl distribution (not abun- scales linked with studies of local demography, for- dance) using playback surveys have been developed est history, and interactions with competitors and and are being used by managers. predators can further our understanding at little expense compared to the potential benefits of man- Response of Boreal Owls to Stand-Level aging forests without adverse effects on boreal owls Habitat Changes and the larger subalpine ecosystem. In this chapter, I will assess the strength of exist- Current knowledge indicates that boreal owls in ing knowledge in forming a conservation strategy. some geographic areas use mature and older forest Then I will discuss some strategies for obtaining habitats for critical life functions. Land managers, needed information. This chapter will include few however, must predict the response of particular citations because it relies on Chapters 9 and 10 which boreal owl populations to various management ac- review literature on this species and some of the for- tions in order to assess the consequences of alterna- ests it inhabits. tives. Our knowledge is not sufficient to complete this task. STRENGTH OF EXISTING KNOWLEDGE Our understanding of habitat use by boreal owls TO FORMULATE A does not allow a ranking of habitats in terms of qual- CONSERVATION STRATEGY ity. Knowledge of habitat use based solely upon ob- servations of habitat use will not be sufficient to Throughout this section I approached each topic guide habitat management. Rather, the relative pro- as a question. Is our understanding of this topic suf- ductivity of owl populations among different habi- ficient to support the development of a sound, na- tats must be discerned in order to provide a ranking tional-scale conservation strategy for the boreal owl? system with which to weigh alternative land man- For example, "is the response of boreal owls to stand agement schemes. level habitat change understood in sufficient detail Even habitat use data are unavailable for most to formulate a conservation strategy?" geographic areas within the species' range. Geo- graphic variation in habitat quality must be docu- Distribution mented and developed into a ranking among habi- tats. Furthermore, proximate and ultimate factors Current knowledge of boreal owl distribution is determining the observed pattern of owl success not sufficient to support the development of con- among habitats must be understood in order to pre- dict habitat use patterns for locales other than those Understanding how owl movements change when studied. In other words, the relationship between individuals encounter landscape boundaries of dif- the owl and its prey, primary cavity nesters, poten- ferent types and the role of corridors in dispersal tial predators, and competitors and habitat relation- will facilitate building models to predict the impact ships of each must be addressed to formulate a pre- of different harvest prescriptions on foraging suc- dictive model useful in evaluating management al- cess. Coordinated investigations examining the re- ternatives. lationship between habitat condition and prey abun- dance would increase the predictive power of such Effects of Landscapsscale Changes on a model. Home Range Use Demography Boreal owl studies have not examined the influ- ence of habitat characteristics at the landscape scale Knowledge of boreal owl demography is not suf- on home range size or the success of individuals. ficient to estimate persistence of either local popu- The literature demonstrates that under some circum- lations or metapopulations. Reproductive rates of stances boreal owls occupy home ranges that exceed boreal owls and the factors determining productiv- 2,000 ha and therefore indicates that management ity are documented for populations in Europe, and for boreal owls must consider extensive landscapes. productivity has been observed for several popula- The available studies do not aid managers in evalu- tions in North America. Age-specific survival and ating different mixes of forest age classes or provide factors influencing survival are virtually unknown. a sound basis for predicting local or regonal varia- Likewise, age-specific dispersal and the factors in- tion in home range use. fluencing immigration and emigration are not un- derstood. The interaction between environmental Effects of Regional-Scale Habitat Changes conditions (forest structure, prey populations, preda- on Movement Patterns tors, competitors, landscape patterns) and demo- graphic parameters must be understood prior to Annual and seasonal movement patterns of bo- developing comprehensive management plans for real owls in North America are virtually unknown. boreal owls. This does not mean that management Without this knowledge the demographic interac- is not possible without data on the demography of tions among populations forming the larger every target population. Rather, patterns of change metapopulation cannot be discerned. Therefore, the in demography across the species' range should be regional effects of local management actions cannot understood so that a reductionist approach to man- be addressed. For example, current knowledge of agement is unnecessary. owl movements is not sufficient to determine Methods to monitor the trend of boreal owls in whether management in montane forests below the selected populations will be necessary to evaluate subalpine zone will influence movements between management practices and facilitate adaptive man- populations. agement responses. Development of methods other than playback surveys has begun (Hayward et al. Effects of Stand-Level Habitat Changes on 1992) but these methods must be validated and re- Foraging Behavior fined if they are to be used effectively by manage- ment. Boreal owl foraging behavior and habitat use is very poorly understood. For instance, the response Dynamics of Primary Plant Communities of foragng owls to landscape boundaries (meadow or clearcut edges, changes in tree density) have not Knowledge of the successional dynamics of sub- been observed. The interaction between prey abun- alpine and boreal forests, while not complete, is ex- dance and habitat structure in determining prey tensive and will facilitate prediction of future forest availability is also poorly understood. The impor- conditions, particularly as that knowledge relates to tance of understanding the foraging ecology of bo- the dominant tree species. Forest ecologists under- real owls cannot be over emphasized. Studies in stand many of the factors related to the occurrence Europe and North America indicate populations are of major natural disturbance agents (fire, insects, frequently food limited. Prey abundance and forag- windfall, and disease). Factors influencing seed ing habitat condition together determine population crops, regeneration and survival of trees, gap dy- trend for many populations. namics, and material cycling have been studied. The 149 stochastic nature of disturbance agents have been knowledge of forest dynamics. Instead, in the sec- incorporated into conceptual models of forest dy- tion that follows, I provide direction in research phi- namics at the stand and landscape scale. losophy and ideas for research approaches. My goal Understanding of the dynamics of forest species is to outline the scope of investigative approaches other than the dominant tree species is less complete. that will be necessary to obtain the knowledge high- The sera1 development of the detritus system, so lighted above. important to subalpine forests, is not understood. Similarly, the dynamics of fungi and lichen popula- Integrate a Variety of Research Tools tions that are important to small mammals have re- ceived little attention. Knowledge of understory- A research program designed to obtain the knowl- plant population dynamics is incomplete. These ar- edge necessary to build a conservation strategy for eas of forest ecology need further attention in order boreal owls will require the integration of several to understand the dynamics of small mammal popu- research approaches. Modeling, field experiments, lations. and observational studies must be integrated so the The population dynamics (production,
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