Richard L. Knight

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.

INFLUENCE OF RECREATIONAL TRAILS ON BREEDING BIRD COMMUNITIES

We investigated the influence of recreational trails on breeding bird communities in forest and mixed-grass prairie ecosystems in Boulder County, Colorado, United States, during 1994 and 1995. Species composition, nest predation, and brood parasitism by Brown-headed Cowbirds (Molothrus ater) were examined near and away from existing recreational trails. Bird species composition was altered adjacent to trails in both ecosystems. Generalist species were more abundant near trails, whereas specialist species were less common. Within the grassland ecosystem, birds were less likely to nest near trails. Within both ecosystems, nest predation was greater near trails. In forests, the rate of brood parasitism was not influenced by trails. No brood parasitism was found in the grassland ecosystem. Our results may be useful to natural-lands managers who must implement management policies regarding the spatial arrangement of trails and trail-use restrictions.

Causes and consequences of expanding American Crow populations

Corvid populations are increasing worldwide in response to urbanization. We investigated the response of American Crows (Corvus brachyrhynchos) to urbanization by (1) comparing rates of winter population change between urban and nonurban locations (using standard Christmas Bird Counts); (2) quantifying population size along a gradient of urbanization in western Washington; and (3) pooling studies from eastern (New York), midwestern (Wisconsin), and western North America (Washington and California) relating survivorship, reproduction, and space use to urbanization. American Crow populations tend to be densest and increasing most rapidly in urban areas of North America. This appears to be facilitated by small space needs of crows in urban relative to suburban, rural, and exurban areas. Crow survivorship is high across the urban gradient, but reproduction and hence population growth, peaks in suburban and rural settings. Local demographic considerations appear unable to account for changing winter crow populations. Rather, we hypothesize that urban crow populations may be increasing primarily as

Impacts of a Severe Drought on Grassland Birds in Western North Dakota

We studied the effect of a severe drought on the population dynamics and community structure of grassland birds in western North Dakota. During the spring and summer of 1988 the northern Great Plains suffered one of the warmest, driest periods in its recorded history. We compared the changes in bird populations and nesting productivity over a 3-yr period before, during, and after the drought. Total grassland bird density declined 61% (P < .05) between June 1987 and June 1988. Densities of six of eight common species declined significantly during the drought. Populations of all but two species recovered in 1989 and total bird density in June 1989 did not differ significantly from June 1987. Species richness and species diversity both declined significantly during the drought and recovered to predrought levels in 1989. Species richness declined more on fair condition than on good condition range during the drought. Vesper Sparrow (Pooecetes gramineus) hatching success, number of young fledged per successful nest, and nesting success were significantly lower in 1988 than either 1987 or 1989. Clutch size did not differ among the three years. The decline in nesting success in 1988 was primarily due to nest abandonment during incubation. Nesting of Vesper Sparrows, Horned Larks (Eremophila alpestris), and Western Meadowlarks (Sturnella neglecta) ended abruptly in mid-June 1988 during a period of extremely hot weather. In 1987 and 1989, nesting continued into July. Despite substantial reductions in bird density and productivity during the drought, many species recovered to predrought levels 1 yr following the drought. This suggests that year-to-year fluctuations in densities of some of these species may not be tightly linked to short-term changes in local productivity. However, sequential years of low productivity may have more substantial effects on these short-lived species. Thus, if drought conditions in North American grasslands become more frequent, as some climate models predict, there could be related changes in the avifauna of the region.

RESPONSES OF RAVEN AND RED-TAILED HAWK POPULATIONS TO LINEAR RIGHT-OF-WAYS

Linear right-of-ways are ubiquitous in the United States and may alter vertebrate populations, yet they remain little studied. We examined the relationship between these areas and common raven (Corvus corax) and red-tailed hawk (Buteo jamaicensis) populations in the Mojave Desert of California by flying helicopter transects along paved highways, transmission powerlines, and control areas (i.e., no highways nor powerlines within 3.2 km). Ravens were equally (P > 0.10) common along highway and powerline transects, but were more (P 0.10) as perch sites. Red-tailed hawks used power poles for both nesting and perching more (P < 0.001) than expected based on availability. Our data suggest that ravens are more abundant along highways because of automobile-generated carrion, whereas both ravens and red-tailed hawks are more common along powerlines because of the presence of superior perch and nest sites. We recommend that land managers evaluate possible changes in vertebrate populations and community-level interactions when assessing the effects of future linear right-of-way projects.

Human disturbance of an avian scavenging guild

In order to investigate the effects of human activities on relationships within foraging guilds, we examined inacanus dynamics of eagles, crows, and gulls scavenging on spawned salmon in the Pacific Northwest. We examined several hypotheses that postulate the asymmetric foraging relationships of the three guild members and that reveal the influence of competition and facilitation in these relationships. Spatial and temporal patterns of resource use by the three primary guild members varied with the presence and absence of human activity at experimental feeding stations. At control (undisturbed) stations, eagles preferred to feed >100 m from vegetative cover, whereas gulls fed <50 m from cover. At experimental (disturbed) stations, eagles rarely fed, and feeding activity by gulls increased at both near and far stations. Crows often fed on alternate food sources in fields adjacent to the river, especially when salmon carcasses were scarce, whereas eagles and gulls rarely did so. We also examined if and how the behavior of single guild members changes in the presence or absence of other guild members. In the absence of eagles, gulls and crows preferred stations far from cover, numbers of both increased at feeding stations, birds were distributed nearer to carcasses, and they fed more. We emphasize that guild theory lends important insights to our understanding of the effects of human disturbance on wildlife communities.

Incorporating Ecology into Land Use Planning: The Songbirds' Case for Clustered Development

Abstract Throughout the American West, private open lands are being converted to a human-dominated residential landscape. This conversion is the foremost threat to wildlife habitat. Pitkin County, Colorado, home to the City of Aspen, is an internationally known example of this land use change. In this article, we describe patterns of development in Pitkin County from the late 1800s through the 1990s. Using field data, we estimate the overall loss of songbird habitat due to two types of residential development, clustered and dispersed, and then examine the types of vegetation most affected. From these data we demonstrate that clustered development, in contrast to dispersed development, can reduce the impact of exurban residential development on wildlife habitat.

Forest roads and landscape structure in the southern Rocky Mountains

Roadless areas on public lands may serve as environmental baselines against which human-caused impacts on landscape structure can be measured. We examined landscape structure across a gradient of road densities, from no roads to heavily roaded, and across several spatial scales. Our study area was comprised of 46,000 ha on the Roosevelt National Forest in north-central Colorado. When forest stands were delineated on the basis of seral stage and covertype, no relationship was evident between average stand size and road density. Topography appeared to exert a greater influence on average stand size than did road density. There was a significant positive correlation between the fractal dimension of forest stands and road density across all scales. Early-seral stands existed in greater proportions adjacent to roads, suggesting that the effects of roads on landscape structure are somewhat localized. We also looked at changes in landscape structure when stand boundaries were delineated by roads in addition to covertype and seral stage. Overall, there was a large increase in small stands with simple shapes, concurrent with a decline in the number of stands > 100 ha. We conclude that attempts to quantify the departure from naturalness in roaded areas requires an understanding of the factors controlling the structure of unroaded landscapes, particularly where the influence of topography is great. Because roads in forested landscapes influence a variety of biotic and abiotic processes, we suggest that roads should be considered as an inherent component of landscape structure. Furthermore, plans involving both the routing of new roads and the closure of existing ones should be designed so as to optimize the structure of landscape mosaics, given a set of conservation goals.

Nest-Defense Behavior of the American Crow in Urban and Rural Areas

The American Crow (Corvus brachyrhynchos) has traditionally been persecuted as a pest and hunted for sport. As recently as 1980 there were an estimated 4,530,000 crow hunter-days in the United States (USDI and USDC 1982a). In recent decades crows, which in the past were typically rural birds, have begun nesting in cities where ordinances prohibit the discharge of firearms. As a result of this colonization of urban areas, two adjacent crow populations exist in many regions, a persecuted rural one and a protected urban one. We took advantage of this situation to examine how the nest-defense behavior of crows has been modified by the presence or absence of persecution. We examined two complementary hypotheses: (1) in an area of high human density and low persecution, crows should habituate to human beings near their nests and (2) in areas of high persecution, crows should show avoidance behavior to human intruders near their nests.

BIODIVERSITY AND LAND-USE CHANGE IN THE AMERICAN MOUNTAIN WEST

Rural private lands in the Mountain West of the United States are undergoing a profound land‐use conversion, from agriculture to low‐density residential or exurban development, though little scientific study documents the ecological consequences of this change. Nongovernmental conservation organizations are working with ranchers to keep rangeland out of development and in ranching, ostensibly because these organizations believe that biodiversity is better protected on ranches than on exurban developments. We compared plant and wildlife communities across the principal rural land uses in the Mountain West: protection, livestock ranching, and exurban development. Native plant and faunal biodiversity was better maintained on ranches and protected areas than on exurban developments. Exurban developments favored species that were nonnative or adapted to human‐altered environments. The continued conversion of ranches to exurban development suggests a long‐term alteration of the regions natural heritage.