Kevin J. Gutzwiller

Wildlife and recreationists : coexistence through management and research

Outdoor recreation has historically been viewed as an environmentally benign activity. Yet with growing numbers of recreationists visiting public lands, and with a greater understanding of the role of public land in safeguarding biodiversity, it is becoming apparent that the effects of recreation on both the environment and wildlife are chronic and pervasive. Wildlife and Recreationists defines and clarifies the issues surrounding the conflict between outdoor recreation and the health and well-being of wildlife and ecosystems. The book is a valuable synthesis of what is known concerning wildlife and recreation. More important, it addresses both research needs and management options to minimize conflicts.

Applying landscape ecology in biological conservation

Foreword--Richard T. T. Forman.- Preface.- Acknowledgments.- Contributors.- Section I. Introduction.- Central Concepts and Issues of Landscape Ecology--John A. Wiens.- Central Concepts and Issues of Biological Conservation--Richard L. Knight and Peter B. Landres.- Broad-Scale Ecological Science and Its Application--Barry R. Noon and Virginia H. Dale.- Section II. Multiple Scales, Connectivity, and Biota Movement.- Spatial Factors Affecting Organism Occurrence, Movement, and Conservation: Introduction to Section II--Kevin J. Gutzwiller.- Patch-, Landscape-, and Regional- Scale Effects on Biota--Kathryn Freemark, Marc-AndrT Villard, and Dan Bert.- Corridors and Species Dispersal--Claire C. Vos, Hans Baveco, and Carla J. Grashof-Bokdam.- Using Percolation Theory to Assess Landscape Connectivity and Effects of Habitat Fragmentation--Kimberly A. With.- Landscape Connections and Genetic Diversity--H. B. Britten and R. J. Baker.- Habitat Networks and Biological Conservation-- Richard J. Hobbs.- Landscape Invasibility by Exotic Species--John L. Vankat and D. Graham Roy.- Section III. Landscape Change.- Conservation in Human-Altered Landscapes: Introduction to Section III.

Does Repeated Human Intrusion Cause Cumulative Declines in Avian Richness and Abundance

Human intrusion, the mere presence of people in the environment, has be- come a dominant form of disturbance in many landscapes. Some forms of intrusion from recreationists and other groups occur repeatedly and can seriously alter avian reproduction, survival, and habitat use. Accordingly, repeated intrusion has the potential to cause impacts that accumulate through time and that are manifested as progressive declines in avian richness and abundance. From 1989 to 1993, we experimentally assessed whether or not temporally cumulative impacts occurred in Wyoming bird communities as a result of re- peated intrusion by solitary hikers; the intrusions lasted 1-2 h each week during 10 con- secutive weeks of each years breeding season. We tested a priori hypotheses about declines in overall richness and abundance, relative richness and abundance for sets of common and uncommon species, richness and abundance for six guilds, and separate abundances of four common species. Relative richness and abundance for the set of common species were the only metrics to exhibit significant declines between years during the 5-yr period. The declines in these variables, however, were not cumulative. At a statistical power level of 0.85, minimum detectable differences for many variables were small enough to have allowed easy detection of substantive declines, had any occurred. The yearly effects we detected for some richness and abundance variables may not have led to cumulative declines because individuals displaced one year may have been replaced in subsequent years, and some individuals each year may have habituated to or learned to tolerate the intrusions. For the avian communities and intrusion levels we studied, managers should focus on trying to preclude or ameliorate short-term impacts. Attempts to identify the types and intensities of intrusion that actually cause cumulative declines in richness and abundance should continue. Data about intrusions that do not generate cumulative declines, such as those presented here, are just as important as data about intrusions that do cause cumulative declines; managers need both to define the scope of intrusion disturbances that can lead to cumulative impacts in avian communities. Information about the cumulative effects of intrusion should be used by conservation biologists, wildlife managers, and land-use plan- ners to decide whether or how to control intrusion.

Conspecific Attraction is a Missing Component in Wildlife Habitat Modeling

Abstract Wildlife biologists use knowledge about wildlife–habitat relationships to create habitat models to predict species occurrence across a landscape. Researchers attribute limitations in predictive ability of a habitat model to data deficiencies, missing parameters, error introduced by specifications of the statistical model, and natural variation. Few wildlife biologists, however, have incorporated intra- and interspecific interactions (e.g., conspecific attraction, competition, predator–prey relationships) to increase predictive accuracy of habitat models. Based on our literature review and preliminary data analysis, conspecific attraction can be a primary factor influencing habitat selection in wildlife. Conspecific attraction can lead to clustered distributions of wildlife within available habitat, reducing the predictive ability of habitat models based on vegetative and geographic parameters alone. We suggest wildlife biologists consider incorporating a parameter in habitat models for the clustered distribution of individuals within available habitat and investigate the mechanisms leading to clustered distributions of species, especially conspecific attraction.

Bird Tolerance to Human Intrusion in Wyoming Montane Forests

Human intrusion can be a serious problem for birds because it can cause displacement, prevent access to resources, and reduce reproduction and survival. The factors that influence avian tolerance to intrusion are poorly understood. We studied passerine responses to intrusion in Wyoming montane forests during the breeding season by using two indices of intrusion tolerance: detectability period, the amount of time that a bird remains near its initial flush point; and approach distance, how close one can get to a bird before it flushes. A solitary observer experimentally approached focal individuals and recorded detectability period, approach distance, the seasonal and daily timing of intrusion, number of nearby conspecifics, number of nearby heterospecific individuals, and surrounding vegetation conditions. Using data from the literature, we also assessed influences of migratory status, body mass, conspicuousness, and height above the ground at which species are active during the breeding season. Detectability period was significantly shorter, indicating intrusion tolerance was lower, when fewer conspecifics were nearby. Approach distance was significantly longer, indicating tolerance was lower, for more-conspicuous species and for species that are active closer to the ground. Effects of other variables studied were not significant. These results demonstrate that social and biological factors can influence tolerance to intrusion. Intrusion-induced behaviors such as nest abandonment and decreased nest attentiveness have led to reduced reproduction and survival in species that are intolerant of intrusion. With knowledge of factors that influence tolerance, the risk of disturbing birds that are sensitive to intrusion could be reduced.

Interception of moving organisms: influences of patch shape, size, and orientation on community structure

Island biogeographers have predicted that in oceanic systems, oblong islands oriented perpendicular to the dispersal paths of organisms should intercept more species and individuals than (1) circular islands of the same size, and (2) oblong islands of equal area oriented parallel to the direction of travel. Landscape ecologists expect similar relations with habitat patches in a terrestrial matrix. Yet in neither situation is there adequate empirical information to permit conclusions about the prevalence of such effects. To test the hypothesis that intercept-related patch variables influence community structure on the landscape scale, we studied relations between the richness and abundance of cavity-nesting birds and patch shape, size, and orientation relative to a northerly migration path. The influences of other patch features on nest abundances were removed analytically. Multiple regression indicated that the mean and total number of nesting species, and nest abundances for migrants were significantly associated with patch orientation or a patch area x orientation interaction, but not patch shape. Nest abundances for permanent residents were not associated with patch shape or orientation, although area effects, possibly reflecting dispersal interception, were evident. These results are consistent with the hypothesis that stochastic interception of migrating or dispersing organisms influences patch community structure. In addition to richness and abundance effects apparent in this analysis, the sex ratio, age structure, growth rate, social structure, and genetic features of patch populations may also be influenced. The interception of moving organisms by patches may thus be a key factor influencing population and community persistence in reserves. If so, landscape structure could be manipulated to maximize the interception of dispersing or migrating organisms, or minimize it if the effects are undesirable.

Effects of human intrusion on song occurrence and singing consistency in subalpine birds

-In 1989, 1990, and 1991, we conducted experiments on 30 circular 1.0-ha sites to assess whether human intrusions during a 10-week period influenced the occurrence and consistency of primary song in breeding subalpine birds. Using only those weekly censuses during which a species was present at a site, we computed song occurrence as the percentage of censuses during which a species sang, and we calculated singing consistency as the maximum number of consecutive censuses during which a species sang. An intrusion bout involved one person who walked through a site for 1 or 2 h. We used a priori contrasts, involving habitat covariates when appropriate, to assess differences in song occurrence and singing consistency between control and intruded sites and between sites at which the inner 25% of the site was disturbed (S25) and those at which 100% of the site was disturbed (S100). Singing by a number of species did not appear to be influenced by intrusion. For several species, however, song occurrence and singing consistency were higher on control sites than on intruded sites, indicating intrusion reduced singing activity. Song occurrence was higher on S100 relative to S25 sites as well. This latter pattern may have emerged because all of the individuals using the S100 sites were able to observe us during repeated intrusions and discern that we were not predators, whereas most of the individuals using the S25 sites likely did not have this opportunity. Thus, some of the individuals using S25 sites may have reduced their singing to avoid detection by us. Because song is essential in territory defense, mate acquisition, and in other reproductive activities, levels of intrusion that alter normal singing behavior have the potential to lower the reproductive fitness of males that are sensitive to this form of disturbance. Received 16 October 1992, accepted 28 January 1993. PRIMARY SONG is loud and far-reaching, occurring most often during the early breeding season and less frequently while young are being raised (Welty and Baptista 1988:224). Two important functions linked to primary song in breeding males are territory defense and mate attraction (Krebs 1977, Eriksson and Wallin 1986, McDonald 1989). Indirect evidence for the territorial function includes observations that most singing occurs during periods of territory establishment and maintenance and is restricted to defended areas (Falls 1988, Welty and Baptista 1988:227, 252). In addition, males countersing with conspecific males on adjoining territories (Wasserman 1977a), and they can be induced to sing with auditory playbacks that 4 Present address: John E. Conner Museum, Texas A&M University-Kingsville, Box 2172, Station 1, Kingsville, Texas 78363, USA. 5 Present address: 1306 Fox Street, Bossier City, Louisiana 71112, USA. simulate territorial intrusion (Falls 1981, 1988). The territory-defense role has been demonstrated experimentally through the surgical muting of males (Peek 1972a, Smith 1979, McDonald 1989), the tranquilizing of males (Peek 1972b), and the use of recorded playbacks (Krebs 1977, Falls 1988). The mate-attraction function of song has been corroborated with observations that singing activity is higher in males before they pair with females than after pairing (Wasserman 1977b). Experimental removal of females from pairs caused significantly higher singing rates by associated males (Wasserman 1977b, Krebs et al. 1981, Cuthill and Hindmarsh 1985). Moreover, males that were surgically muted were unable to attract females (e.g. McDonald 1989), even when such males possessed territories in good habitat and unmated females were present in the area (Peek 1972a). Because singing is important in territory defense and mate attraction, human disturbance that alters singing behavior may influence a

Auditory Sampling of Frogs: Detection Efficiency in Relation to Survey Duration

Abstract Call surveys are used widely to assess distribution and abundance of anurans. The durations of these surveys often are based on convenience rather than on empirical analysis. Knowing how frog detection varies with survey duration is valuable for designing sampling schemes, yet few studies have examined the relationship between survey duration and detection efficiency. We conducted call surveys for frogs in central Texas to assess effects of survey duration on detection efficiency. We controlled analytically for temporal and environmental covariates that had the potential to confound our assessment of survey duration. Cumulative detection efficiency of all species was 94% for 15-min surveys and did not increase appreciably with longer durations up to 30 min. Detection efficiency for number of species was significantly higher for 15-min surveys than it was for 5-min surveys, and the variability of detection efficiency decreased with increasing survey duration. Detection efficiency for number of calling individuals of Acris crepitans and Rana sphenocephala did not differ among 5-, 10-, and 15-min surveys. Of the temporal and environmental covariates examined, only the year in which a survey was conducted was significantly associated with detection efficiency for number of species. None of the covariates was significantly related to detection efficiency for A. crepitans or R. sphenocephala. When sampling resources such as time and personnel are limited, knowledge about detection efficiencies is essential for allocating survey effort.

Influences of roads and development on bird communities in

Our objective was to improve knowledge about effects of broad-scale road and development variables on bird communities in protected desert landscapes. Bird species richness and the relative abundance or probability of occurrence of many species were significantly associated with total length of roads within each of two spatial extents (1- and 2-km radii), distance to the nearest road, distance to the nearest development, or the two-way interactions of these variables. Regression models reflected non-linear relations, interaction effects, spatial-extent effects, and interannual variation. Road and development effects warrant special attention in protected areas because such places may be important sources of indigenous bird communities in a region.

Repeated human intrusion and the potential for nest predation by gray jays

Through attraction of avian nest predators, human activity near nests is known to cause lower nesting success or nest failure in some species. This is a significant conservation issue because many wildlands are subjected to repeated intrusion by recreationists, ecotourists, and other user groups during avian breeding seasons. Yet, wildlife scientists still have limited knowledge about the extent to which repeated human intrusion attracts avian nest predators. We studied this topic in subalpine forest in Wyoming, USA, and experimented with the gray jay (Perisoreus canadensis), a nest predator that is known to approach recreationists. During 1989-1993, we implemented intrusions within 20 circular 1-ha (113-m-diam) sites for 1 or 2 hr each week during a 10-week period when potential passerine prey were breeding. Simultaneously, 10 circular 1-ha control sites did not receive experimental intrusions. The average number of gray jays on intruded sites was higher than that on control sites by 156% (1989), 225% (1990), 59% (1991), 13% (1992), and 29% (1993). The probability of gray jay recurrence on intruded sites was higher than that on control sites by 125% (1989), 300% (1990), 20% (1991), 33% (1992), and 20% (1993). By increasing the number and recurrence of gray jays, relatively low levels of repeated intrusion can increase the potential for nest predation by gray jays. We caution that additional work is necessary to assess whether attraction of gray jays actually leads to increased nest predation. Knowledge of when intrusion does and does not attract gray jays is important because information about both events is necessary to define the levels and circumstances of intrusion that are influential. Wildlife managers can use knowledge about intrusion-induced attraction of avian nest predators to help decide whether or how recreational activity in wildlands should be managed.