General Technical Report RMRS-GTR-22
The Northern Goshawk in Utah: Habitat Assessment and Management
Recommendations
General Technical Report RMRS-GTR-22
The Northern Goshawk in Utah: Habitat Assessment and Management Recommendations
Executive Summary
This assessment describes northern goshawk (Accipiter gentilis) habitat in the State of Utah. It can be used in both regional and sub-regional level planning. At these levels, this assessment should (1) provide information on the location and connectivity of habitat that can be used to make more informed decisions for managing both public and private lands; and (2) complement other regional assessments such as the Interior Columbia Basin (Quigley and others 1996) or the USDA Forest Service Intermountain Region's Proper Functioning Condition assessment (USDA Forest Service 1997).
At the local level (forest level and lower) this assessment outlines a process that should be used to describe goshawk habitat, proper functioning condition, or other forest or woodland characteristics of interest. At this level, fine resolution data should be used to describe these characteristics, and this assessment can be used to provide context. In addition, at this level, the management recommendations for the northern goshawk in the Southwestern United States (Reynolds and other 1992) should be used to help prepare site prescription. Data in this assessment are too coarse for making site specific prescriptions and should only be used to provide context and describe processes when used at these levels. In addition, this assessment does not prescribe implementation methods. It describes desired conditions, with managers needing to decide how and if they will be used. This assessment describes goshawk habitat and does not describe goshawk demographics, nor does it directly address goshawk population viability.
Issue
Changes in forest structure, large tree removal, and other forest developments singly or in combination may negatively affect northern goshawk populations (Crocker-Bedford 1990). These changes in habitat could be associated with timber harvest, changes in fire regimes, insect and disease epidemics, or with livestock grazing or all these activities. Perhaps one of the greatest impacts on habitat loss is the lack of fire within the ecosystem. Successful fire exclusion, by altering native successional pathways, has dramatically altered forested ecosystems exemplified by ingrowth of shade-tolerant tree species throughout Utah. With these changes in habitat came suspected declines in goshawk populations in much of the Southwestern United States (Bloom and others 1986; Herron and others 1985; Kennedy 1989). Because of these suspected declines in goshawk population in July 1991, the USDI Fish and Wildlife Service announced a 90 day finding for a petition to list the northern goshawk in Utah, Colorado, New Mexico, and Arizona as endangered and to include critical habitat (USDI Fish and Wildlife Service 1997). Since this petition's acceptance, the USDI Fish and Wildlife Service determined that listing the northern goshawk as endangered was not warranted. Through court action in 1992 and 1997, the USDI Fish and Wildlife Service was ordered to revisit its decision, and ordered the agency to address the status of the goshawk in the Western United States.
Questions
To address the issue of declining goshawk habitat in Utah, the technical team, in consultation with forest managers, developed the following questions to guide the assessment:
1. Is there adequate nesting habitat available?
2. Is there adequate foraging habitat available?
3. Are northern goshawks able to move freely between habitat patches?
4. Is the population viable at the State level?
5. Where is the high value habitat?
6. How are current management policies affecting goshawks?
7. What are the important habitat trends and their implications for goshawks:
This assessment will attempt to address these questions.Northern Goshawk and Its Habitat
Distribution of the goshawk is Holarctic with three recognized subspecies breeding in North America: the northern goshawk (A.g. atricapillus), Queen Charlotte (A.g. laingi), and the Apache (A.g. apache) (USDI Fish and Wildlife Service 1997). The northern goshawkhereafter referred to for the sake of brevity as "goshawk" is the largest and most widespread of the three subspecies of the genus Accipiter in North America. The goshawk lives in a variety of forest cover types throughout the State of Utah ranging from the subalpine environments typified by Engelmann spruce (Picea engelmannii) and subalpine fir (Abies lasiocarpa) to pinyon/juniper (Pinus edulis/Juniperus osteosperma) woodlands bordering the grass and shrub lands. The forests in which goshawks forage and nest have been impacted by effective wildfire suppression throughout the West (Dieterich 1983; Keane and others 1990; McCune 1983; Stein 1988; Weaver 1961). Large numbers of seedlings and saplings in many forests have created "ladder" fuels that carry fires from the surface into the crowns (Madany and West 1980). This condition combined with a build-up of surface fuels, produces severe and intense crown fires.
Habitat Assessment
This assessment describes goshawk habitat for the State of Utah, the area in which recommendations and inferences as to the status of goshawk habitat were requested by the involved and cooperating parties. To understand the processes influencing goshawk habitat in Utah, and to disclose more immediate threats and risks to goshawk habitat in the State, a smaller geographic area was required. This geographic unit needed to provide interpretive power and be spatially explicit across the forest and woodlands of Utah, independent of ownership or administrative boundary. The geographic unit that was chosen was defined by potential vegetation. This classification system integrates a variety of physical and biological components including climate, soils, geology, and vegetation. For the assessment of goshawk habitat in Utah, we chose eight potential vegetation types.
Potential vegetation types were not delineated for Utah. Therefore, using Geospatial Analysis Processes data to identify patches of vegetation, 1,112 vegetative polygons of the forest and woodlands of Utah were identified. To each of these polygons, the potential vegetation type was assigned using inventory plot data points located near or in the polygon, and by local knowledge supplied by resource managers familiar with the area (table E1). Inventory points were random plots sampled by the Forest Inventory and Analysis (FIA) group of the Rocky Mountain Research Station. To each of the potential vegetation type polygons current vegetation was determined using a combination of potential vegetation type, Geospatial Analysis Processes, and FIA data along with expert knowledge (table E1).
Each vegetative polygon is the State was evaluated by wildlife biologists, as to their value for goshawk foraging and nesting. Each polygon was rated as high, medium, or low quality in four categories: goshawk nesting habitat, small to medium-sized mammal habitat, woodpecker habitat, and habitat for other medium-sized birds. These ratings were used to produce a combined goshawk rating for each of the polygons in the State. Areas were rated as high value habitat if they were rated high for nesting as also rated high for at least one prey group. This combined habitat rating would include areas where populations of one or two of the prey groups are expected to be abundant.
Habitat is connected and available to goshawks if it is accessible from existing population centers. If every patch can be reached and subsequently occupied, then all areas could be considered connected. Connectivity has positive implications for population viability because it allows individuals to emigrate to new areas with their current habitat declines in value. Connected habitat patches ensures that individuals will be available to re-colonize habitats or emigrate to new breeding territories throughout the State.
Although goshawks are clearly capable of traveling long distances to find suitable habitat, information available indicates that 20 to 60 mile movements are typical. Therefore, a maximum distance of 60 miles between patches of high value habitat would represent a conservative method of defining connectivity. This definition ensures that goshawks will be able to disperse freely throughout the State, always finding high value habitat (map E1).
The forests and woodlands of Utah are dominated by late seral species (table E2). Depending on the potential vegetation type, white fir (Abies concolor), subalpine fir (Abies lasiocarpa), Douglas-fir (Pseudotsuga menziesii), pinyon pine, and juniper often dominate the forests. In addition, most forests contain many seedlings and saplings, creating dense forests prone to insect, disease, and stand replacing fires. Ponderosa pine (Pinus ponderosa), quaking aspen (Populus tremuloides) and lodgepole pine (Pinus contorta), which are early and mid-seral species in most potential vegetation types, are often poorly represented. Moveover, quaking aspen is one of the most important cover types supporting goshawks in Utah. Forests dominated by late seral species in general are more unstable in both the short- and long-term than forests dominated by early and mid-seral species. In addition to being unstable and at risk to stand replacing fires because of dense stands with many canopy layers, these same conditions make them undesirable for both nesting and foraging by goshawks.
Table E2 -- Proportion of each potential vegetation type currently in various forest cover types.
No other potential vegetation type is so dominated by late seral species as pinyon/juniper (table E2). With this condition and the indeterminate successional pathways present, the short-term prognosis for the type is a continued dominance of pinyon and juniper. Throughout the State, attempts to convert stands to early and mid-seral stages have had limited success. The introduction of exotics (cheat grass, Bromus tectorum) also changes successional pathways and alters fire regimes.
Owners or administrators of the forests and woodlands of Utah include these entities: the USDI National Park Service, USDI Bureau of Land Management, USDA Forest Service, private, State of Utah and Native Americans. By far, the USDA Forest Service administers the majority of the forests and woodlands in Utah. Also, these lands contain the majority of the high and medium valued nesting habitat, and the majority of the high value combined foraging and nesting habitat.
The USDA Forest Service manages lands for a variety of objectives ranging from intensive forest management to recreation. Range management is emphasized on 17 to 23 percent of the forest and woodlands, and timber is emphasized on up to 58 percent, depending on the potential vegetation type. Also, much of the lands in which range is emphasized are rated high or medium for nesting (table E3). In terms of overall habitat, 34 percent of the lands with a range emphasis were rated as high value habitat and 43 percent of the mixed use areas were rated as high quality habitat (table E3). These management directions can decrease prey habitat by removing cover and food for prey species. Also, indirectly, they can interfere with fire regimes and native forest succession. Depending on the intensity and duration, grazing could be detrimental to goshawk habitat and to quaking aspen stands.
Recommendations
The forest and woodlands of Utah providing goshawk habitat are diverse in species composition and structure. The history of land-use in Utah is highly variable, ranging from domestic livestock grazing to tourism and snow skiing. With these land uses came the desire to protect forests and woodlands from fire. Effective fire exclusion began in the mid-1900's. As a result, the forests and woodlands of Utah are now dominated by dense stands of late seral species, which are prone to epidemics of diseases and insects and stand replacing fires.
The conservation of the northern goshawk will require the restoration and protection of degraded habitats and native processes. The following recommendations describe actions aimed at sustaining habitat for the goshawk and selected prey in the forests and woodlands of Utah. The applicability for meeting these recommendations is the responsibility of the specific land owner or administrator. Because these recommendations are directed at habitat and native processes, they will also benefit a myriad of other plant and animal species.
- Increase early and mid-seral species using mechanical means or fire or both.
- Evaluate activities near the edges of high value habitat as to how they may impact the connectivity of habitat, irrespective of ownership.
- Increase the numbers and distribution of large trees in the landscape.
- Maintain large trees in nest sites.
- Develop properly functioning systems at both the regional and landscape level.
- Ensure that in lodgepole stands a seed source is present when applying treatments.
- Recognize that long persistent quaking aspen can successfully regenerate under an existing canopy.
- Recognize that the successional pathways of pinyon/juniper potential vegetation types are indeterminate, and in general most of the conditions after disturbance are less stable than the present late seral condition.
Assessment Questions
1. Is there adequate nesting habitat available?
Presently there appears to be adequate nesting habitat in Utah to maintain a breeding population of goshawks.
2. Is there adequate foraging habitat available?
Based on prey habitat, it appears that foraging habitat is presently available throughout the State.
3. Are northern goshawks able to move freely among all available habitat patches?
Yes, goshawks appear to be able to move freely among habitat patches throughout Utah.
4. Is the population viable at the State level?
This assessment cannot answer the question of population viability directly because there are inadequate demographic data available. In general, existing habitat appears to be capable of supporting a viable population of goshawks at the State spatial scale. However, even though high quality habitat does not appear to be lacking, Statewide, habitat deficiencies may be present at the local level.
5. Where is the high value habitat?
High value habitat is distributed throughout the State (map E1).
6. How are current management policies affecting northern goshawks?
Current management policies are affecting northern goshawks in a variety of ways. On USDA Forest Service administered lands, 20 percent of the high value habitat is being managed with a timber emphasis, 35 percent with mixed uses, and 27 percent with a range emphasis. Each of these management categories allows for activities that either can degrade or improve goshawk habitat. Information in this assessment does not reveal any substantial deficiencies in habitat quality in any management category. There are two possible explanations for these results: (1) management activities are having no negative effect on goshawk habitat, or (2) management activities are having some negative effects on goshawk habitat, but the effects are not detectable at either scale used in this assessment. We currently have no data available to determine which is true. Current management policies have the potential to degrade habitat if any one activity is over-applied or mis-applied. Thus current management policies provide for a wide range of implementation options, with a correspondingly wide range of possible effects on goshawk habitat. The critical decisions are those being made on individual project level analyses, because this is where managers can use the best available information in ensure that projects are providing for goshawk habitat needs.
7. What are the important habitat trends and their implications for goshawks?
The most obvious trend in Utah forests and woodlands is the lack of early and mid-seral species in all of the potential vegetation types. If forest management stresses proper functioning conditions, the importance of large trees, maintaining native processes, using adaptive management, and recognizing the role of fire, the habitat outlook could be favorable for the goshawk and its prey. Urbanization and more intensive uses of the forests by humans could degrade goshawk habitat, especially on private lands. This trend could also affect the connectivity of the habitat across the State.
Title: Executive
Summary: RMRS-GTR-22 - The Northern
Goshawk in Utah: Habitat Assessment and Management Recommendations
Electronic Publish Date: May 26, 1999
Expires: Indefinite
Last Update: January
15, 2002