Northern goshawk ecology: effects of scale and levels of biological organization-Abstract
John J Keane and Michael L Morrison

We develop a conceptual framework that addresses the effects of scale and levels of biological organization on ecological studies. We specifically consider northern goshawk (Accipiter gentilis) ecology relative to this framework. Traditionally, ecological studies have emphasized phenomenological, rather than mechanistic, explanations of ecological phenomena. Emphasis has focused on describing the general patterns of "how" an animal interacts with the environment. Less effort has been directed towards determining "why" we observed particular patterns; that is, what are the basic biological and ecological reasons for the phenomena that we observe? In our study area in the Sierra Nevada, California, we observed both individual and seasonal variation in the size of goshawk home ranges. We are developing an energetics model of goshawks and conducting detailed studies of the prey species used by goshawks. We will use these data to build up form an intensive understanding of the factors influencing an individual to explain the patterns at the more extensive scales. We argue that the intensive and extensive data needs that are required to develop conservation strategies should be based on a mechanistic understanding of the patterns observed. Predictions derived form phenomenological models assume that the conditions on which the model was constructed do not change. However, conservation planning requires quantitative predictions for systems that are often dynamic in both space and time, such as forests managed for timber production. Thus, emphasis should be placed on developing a mechanistic understanding of particular ecological phenomena to improve the predictive ability of conservation planning.

Sustaining forest habitat for the northern goshawk: a question of scale--Abstract
Russel T Graham, Richard T Reynolds, M Hildegard Reiser, Richard L Bassett, and Douglas A Boyce

The nest area, post-fledgling family area, and foraging area are critical home range components for maintaining northern goshawk (Accipiter gentilis) populations. Each of these forest components has a specific purpose in the life history of the northern goshawk and each contains several important attributes, ranging from forest structure to forest floor characteristics. The way in which home range components in a forest regenerate, develop, and die is highly variable, both temporally and spatially. Therefore, forests need to be regenerated and tended to ensure that a portion of a goshawk's home range is n old forests indefinitely. This can be best accomplished by analyzing and managing large tracts of forests as sustainable ecological units rather than managing smaller tracts of forests as individual home ranges.

Assessment of goshawk nest area habitat using stand density index-Abstract
Robert J Lillieholm, James N Long, and Susan Patla

The manipulation of stand density to create a specified stand structure in the future represents a powerful tool in wildlife habitat management. Controlling stand density, and ultimately stand structure, through initial tree spacing and/or subsequent thinning is critical achieving many specific stand management objectives. Indices of relative stand density, based on average tree size (e.g., mean weight, volume, height, or diameter) and stand density (e.g., trees per hectare) are useful in characterizing current and future stand structure. This paper describes Reineke's stand density index (SDI), and demonstrates its application to the management of northern goshawk (Accipiter gentilis) nest area habitat.

Northern goshawk broadcast surveys: hawk response variables and survey cost-Abstract
Suzanne M Joy, Richard T Reynolds, and Douglas G Leslie

We examined responses of northern goshawk (Accipiter gentilis) to taped broadcast calls of conspecifics in tree-harvest areas and around alternate goshawk nests on Kaibab National Forest, Arizona, in 1991 and 1992. Forest areas totaling 476 sq. km. Were systematically surveyed for goshawks. Ninety responses by adult and juvenile goshawks were elicited and 15 active nests were located. No difference in response rates between sexes was detected. Adult males, however, tended to approach the broadcaster without vocalizing, whereas adult females approached while vocalizing. Our success in finding active nests after getting responses from females was greater than after male responses. Goshawks responded more often to broadcasts during the nestling (2.0 responses/100 stations) than fledgling (1.0 responses/100 stations) period. During the fledgling period, adults were more likely to respond to broadcasts than juveniles. Total costs associated with our surveys for goshawks were $58-82 per sq. km. And $4.15-5.80 per broadcast station, depending on salaries.

Influence of site quality and stand density on goshawk habitat in southwestern forests-Abstract
Richard L Bassett, Douglas A Boyce, Jr., M Hildegard Reiser, Russell T Graham, and Richard T Reynolds

Current management guidelines for the northern goshawk (Accipiter gentilis) in the Southwest call for a mosaic habitat consisting of approximately 10 percent of the forest area in grass-forb/shrubs, 10 percent in 2.5-12.7 cm trees, 20 percent in 12.7-30.5 cm trees, 20 percent in 30.5-45.7 cm trees, 20 percent in 4.57-61.0 cm trees, and 20 percent in 61.0 cm or greater trees. This habitat mosaic was conceived as convenient categories to describe a generally balanced, ecologically sustainable, forest ecosystem. In reality, however, the vegetative structural percentages vary greatly. We describe how differences in site quality and stand density affect vegetative structural stage percentage and forest age.

Macrohabitat selection by nesting northern goshawks: implications for managing eastern forests-Abstract
Thomas Bosakowski and Robert Speiser

Macrohabitat data from 16 northern goshawk (Accipiter gentilis) nest sites and 70 random sites in the New York-New Jersey Highlands were analyzed. Variables included distances to human habitation, paved road, water, wetlands, and forest openings, elevation, and slope, slope location, and slope aspect. Univariate tests revealed that macrohabitat was important to nest site selection in goshawks since several variables were significantly different than random sites (disturbance due to human habitation, paved roads, and elevation). In addition, slope aspect data revealed that nesting on southern aspects (SW, S, SE) was avoided. A full-model discriminant function analysis (DFA) was used to determine the extent of overlap between random sites and nest sites. The DFA was able to correctly classify 69% of nest sites and 79% of random sites, further demonstrating that macrohabitat plays an important role in nest site selection. A management model using stepwise DFA revealed that distance to paved road and elevation were the most important discriminating variables. These variables indicated that the goshawk may be an area-sensitive species, since smaller forest tracts bounded by paved roads were not used for nesting.