Northern Goshawk Facts

Accipiter gentillis

    The northern goshawk is the largest of the North American "true hawks". An adult goshawk is 21-26 inches long with a wing span of 40-46 inches. The females are usually larger than the males. The goshawk lives in the forest and has sharp claws and beak to tear at flesh. They hunt medium to large sized birds and mammals such as birds of the forest, ducks, gulls, squirrels and snowshoe hares. When a goshawk kills its prey they usually prepare it on a tree separate than their nesting tree. Goshawks usually place their nests on the tops of old growth forests were they feel protected against unwanted visitors. They are highly sensitive to disturbance around the nesting site such as logging and skidding activities. Extensive logging of old growth forests on federal, state and privately owned lands has caused the goshawk population to decrease. They are a good indicator species of old growth forest health.

 

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Goshawk nest in the Children's Forest.

 

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Goshawk photographs compliments of Kieran Suckling of the Southwest Center for Biological Diversity.

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In 1991, the Southwest Center for Biological Diversity petitioned the U.S. Fish & Wildlife Service to list all goshawks in the western U.S. as endangered. Because of the tremendous blow this would deliver to the timber industry, the agency twice turned the petition down. Both times, however, they took them to court and won prompting a federal judge to note that the agency seems to have a policy against listing species as endangered if they live in trees valued by the timber industry. A ten year battle continues and a 3rd lawsuit has been filed to add the Northern Goshawk to the endangered species list. The listing would also preserve old growth forests in every western state. Logging is the primary threat to goshawks. Cattle grazing, mining, recreation, road building and other forest disturbances are also threats.

For more goshawk information you can surf these websites:

Center for Biological Diversity

Predator Conservation Alliance

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Goshawk feathers.

 

Goshawks in the News

SUIT FILED TO PROTECT SW GOSHAWKS- SEEKS
LOGGING BAN ON ELEVEN NATIONAL FORESTS

On 9-5-00, the Center for Biological Diversity and the Grand Canyon Chapter of the Sierra Club filed suit against the U.S. Forest Service to stop all logging on the eleven Arizona/New Mexico national forests until a
new goshawk management plan is devised that will adequately protect mature and old growth forests. Over the objection of the U.S. Fish & Wildlife Service, the Department of Interior, the Arizona Game and Fish
Department, the New Mexico Department of Game and Fish, and scientists from within the Forest Service and academia, the Forest Service adopted a management plan in 1996 which allows extensive logging within goshawk home ranges and encourages forest fragmentation. The suit seeks to strike down the plan and halt logging until a scientifically credible plan is devised.

On other fronts, the Center is currently litigating to protect the Queen Charlotte goshawk as an endangered species in the Pacific Northwest (Southeast Alaska, insular British Columbia, and western Oregon and Washington) and the Northern Goshawk in every western state from Washington to New Mexico. In the Sierra Nevada, it joined a coalition appealing the Quincy Library timber project and is commenting on a regional plan to conserve habitat for goshawks, spotted owls and mammalian predators.

The Center's goshawk webpage has photographs, a copy of the current lawsuit, excerpts from state and federal agencies and scientists opposed to the Forest Service plan, a review of the impact of logging on goshawks, and an early version of the Forest Service plan before it was modified by timber industry pressure to allow more logging. http://www.biologicaldiversity.org/swcbd/species/goshawk/goshawk.html

The suit is being argued by Mike Lozeau and Deborah Sivas of Earthjustice (Palo Alto).

The Oregon Department of Forestry is planning to leave 1.6 acres as a no cut zone
around the northern goshawk nest in The Children's Forest, and leave more trees in another almost 5 acres.

Is this good wildlife biology?

 GOSHAWK RESEARCH AND MANAGEMENT PLANS IN OREGON AND NORTHERN CALIFORNIA

(Provided by Kieran Suckling of the Center for Biological Diversity)

Northern California U.S. National Forest Goshawk Management Plans

Shasta/Trinity 150 acre no logging buffer around nest
Mendocino 300 acres of a 500 acre nest buffer to remain in mature forest. A 1,500 acre foraging surrounding this must have 60% in mid to mature forest.
Klamath 300 acres of a 500 acre nest buffer to remain in mature forest. A 1,500 acre foraging surrounding this must have 60% in mid to mature forest.
Six Rivers 300 acres of a 500 acre nest buffer to remain in mature forest. A 1,500 acre foraging surrounding this must have 60% in mid to mature forest.
 

DESIMONE STUDY

Desimone, S.M. 1997. Occupancy rates and habitat relationships of northern goshawks in historic nesting areas in Oregon. M.S. Thesis, Oregon State University, Corvallis, OR.

Goshawks in eastern Oregon occupied historic territories 29% of the time and recently discovered/occupied territories 79% of the time. Sixty percent of recently discovered/occupied nest sites were in old, closed canopied forests (>15 trees/ha >=53 cm (21") dbh, >50% canopy cover), 26% were in mid-aged, closed forest (23-53 cm dbh, <15 trees/ha >53 cm (21") , >50% canopy closure). The 15 historic nest sites which continued to be occupied had significantly more mid-aged, closed forest and old, closed forests than the 31 historic nest sites which were unoccupied. This relationship was significant within 12, 24, 52, 120, and 170 ha circles surrounding goshawk territory centers.

Nest success of occupied/historical sites (70%) and young per nest (1.5) was comparable to recently discovered/historical sites (77% and 1.39).

The occupancy rate of recently discovered territories (79%) was similar to rates of recently discovered territories in AZ, NM, CA, UT and OR (range= 66%-74%) that had a low level of habitat disturbance. The occupancy rate of historic territories, however, was only 29%. All of the unoccupied/historic territories had logging within the 52 ha nest site: "this strongly suggests that the low detection rate…was largely the result of habitat alteration; i.e. the conversion of Late Closed and Mid-aged Closed forest conditions to mainly Very Early seral stage of Early Open canopy forest conditions within the 52 ha alternate nest cluster."

As of 1994, only 2-8% of the Freemont National Forest is in late successional pine types (page 55, Henjum et al. 1994:5). Using historic goshawk nests, late closed forests decreased 50% since the 1970s, mid-aged closed forest 20%-40%,. Very early forest increase 400% to 1,000%, early open forest increased as well (Table 11, figure 5).

Good discussion of accipiter reoccupancy rates (p. 56).

Tree harvest prescriptions that create large areas with sparse cover (e.g. Very Early, Early Open, Mid Open, Late Open) are potentially detrimental to goshawk occupancy, especially if the percent of open canopy (<50% CC) forest is >33.7% (mean) at the 52 ha scale or >43.8% (mean) of the total area of the 170 PFA (Table 12)."

"Analysis of the Fremont vegetative cover types suggests that any habitat manipulation resulting in substantial reduction of mature, closed-canopy forests, which is subsequently replaced by early successional or more open young forest, would reduce the suitability of an area as a potential nest site (McCarthy et al. 1989)…My analysis suggests that more severe alterations (regeneration clearcuts, partial removal of stands resulting in <50% canopy closure, and moderately high to severe alteration) may be better predictors of goshawks not nesting in areas where nest site potential has significantly deteriorated and become non-suitable for nesting."

  • "I suggest a 52 ha (130 acres) no-harvest zone within the alternate nest cluster and discourage further cutting of large, late and old structure trees (>53 cm) within the PFA to preserve stand integrity, maintain closed canopies, maintain connectivity to alternate nests stands, and optimize conditions for breeding goshawk pairs to persist. The delineated 52 ha should include at least 2 alternate nest stands in addition to the existing nest stand and should have similar suitable structural conditions as the known nest area. Nest stands should be delineated to include the most late-successional, closed-canopy forest structure surrounding the nest trees as possible (a minimum of 30% of the 12 ha nest stand [this study]). Outside the 52 ha nest cluster, the remainder of the 170 ha PFA should retain all existing Mid-age and Late vegetation structure possible. I recommend that <20% of the PFA should be in Very Early and Early Open vegetative cover types." Ed: This also suggests that occupancy rates of recently discovered territories is not an indicator of changes in total occupancy rates or population densities.

Within the 52 ha scale, occupied/historic nest sites had 49% total old closed and mid-aged closed forest, while unoccupied/historic nest sites had 19% total old closed and mid-aged closed forest. The current relationship between forest structure and occupancy matches the historic relationship: all historic nest sites averaged 51% total old closed and mid-aged closed forest when last known to be occupied prior to the study. At the 12 ha level, occupied/historic nest sites had 400% more old closed forest than unoccupied/historic nest sites.

The Freemont National Forest (Oregon) summarized the recommendations of Desimone (1997) as such:

"These studies represent the best information available...[Desimone] confirmed the importance of late closed and mid-age closed forests as indicators of quality habitat within the 52 ha scale on historic nest sites where goshawks were still present in 1994...suggesting that little or no habitat alteration within aggregate nest stands is important to ensure persistence of nesting pairs."

 

MCGRATH STUDY

McGrath, M.T. 1997. Northern goshawk habitat analysis in managed forest landscapes.M.S., Oregon State University, Corvallis, OR.

82 active nest and 95 random sites were analyzed in eastern Oregon and Washington.

Nest sites (1 ha) typically occurred on the lower 1/3 or bottom of a north facing slope. They had higher basal areas, larger trees, higher canopy closure, and greater live stem density compared to random sites. Mean age was statistically greater than average (by 11 years) and mean distance to human disturbance was less (by 8 m) than random sites, but were not likely biologically detectable to goshawks.

Nest stands (10 ha) were in mid-old forests with canopy >=50%.

Theoretical PFAs excluding the nest stand (10-83 ha) were negatively correlated with early forest conditions.

PFAs (170 ha) were not different from random sites.

 

NORTON STUDY

Norton, B.E..1994.Characteristics of northern goshawk (Accipiter gentilis atricapillus) nest sites within the Siskiyou Mountains of northern California and southern Oregon. Rogue River National Forest, Medford, OR.

All five known goshawk nests on the Applegate Ranger District of the Rogue River National Forest (OR) were in old growth or mature stands though such forests make up only 39.37% of the district. The nests, however, were found during timber harvest surveys rather than by random or systematic surveys.

Mean canopy closure, as measured by spherical densiometer, of four active nest stands was 88% (range = 75-97). Mean nest stand size was 851.4 acres, while the average mature/old growth stand on the district is 118.6 acres.

Nests were in Douglas-fir, ponderosa pine, and madrone. Mean nest tree DBH was 81.84 cm (32.22 in.) (range = 50.80 - 124.46 cm). Two of four nests were in mistletoe clumps.

Average nest height was 18 m (59 ft) (range = 12 - 24 m). All nests were within the lower 1/3 of the canopy.

Nest sites were on "relatively moderate" slopes for the areas (average 36%, range = 27-58%) with north and east aspect.

Mean distance to riparian area was 436 m (range = 180 - 660).

Mean distance to road was 1,198 m (range = 180 - 3,300).

Understories were "open" but not quantified.

Ponderosa pine and Douglas-fir were the dominant overstory trees.

 

ALLISON STUDY

Allison, B.A. 1996. A landscape characterization of nesting goshawk habitat in northern California using remote sensing and GIS. M.S. Thesis, Southern Illinois University at Edwardsville, Edwardsville, IL.

100% of 16 nests systematically found in two survey areas (13,360 and 14,250 ha) were in mature-old forest stands on north facing slopes. Most were between 1,700 and 1,900 m in elevation and on <20% slopes

The amount, size of patches, edge density, and edge contrast of light density and dense mature-old forest was significantly greater in goshawk nest stands and within 800 m (= 500 acres = .5 mile radius) of nests than in control plots. Larger amounts of old growth within 800 m may be more important on less mesic sites.

80 ha (200 acres) of light density and dense mature-old forest should be maintained within 800 m of goshawk nests. Lodgepole stands and meadows should be maintained. Protection of meadows and riparian areas is also important for adequate prey populations, and the homogenous distribution of different vegetation types and seral stages should also be maintained to provide high contrast edge for foraging.

 

BLOOM ET AL.

Bloom, P.H., G.R. Stewart and B.J. Walton. 1986. The status of the northern goshawk in California, 1981-1983. California Fish and Game Department, Sacramento, CA.

Statewide, five to ten territories are being destroyed yearly due to logging. Between 1981 and 1983, six territories on National Forest lands were lost to logging. Some inactive territories had extensive logging in them.

Goshawks are doing poorly in the Northern Coast Ranges-Klamath Mountains and on the east side of the Sierra Nevada.

The Forest Service should increase protected nest stands from 10-32 ha (25-80 acres) to a minimum of 50 ha (125 acres), and increase the total number of protected territories. "In our judgement, this still places territories at risk and only selective cutting should be permitted adjacent to this area." "protecting only a nest stand probably is not adequate to maintain a productive territory."

If prey densities are high, logging is light, and forest buffers are left around nest stands, then 25-80 acre nest stand may be adequate.

 

FOWLER

Fowler, C. 1988. Habitat capability model for the northern goshawk. USDA Forest Service Region 5, Tahoe National Forest, Nevada City, Nevada. 21 pp.

Minimum nest stand should be 50 ha (124 acres). "Stands less than 50 ha will reduce protection from disturbance and increase the possibility of inactivity and abandonment."

"Where management for the current population is desired, establish at least four territories per township across suitable habitat" (3.5 to 10 miles between territories).

  • "Integrating goshawk habitat with pileated woodpecker and spotted owl management areas "should be done with caution or avoided because of the potential for goshawk predation on these species."

"Preponderance" lands within goshawk territories should have overstories trees averaging 25-30" dbh exceeding 60% canopy closure. The nest core should not by isolated by logging.

Maintain meadows and streams. Edges increase prey diversity, but are probably not a limiting factor.

 

SAUNDERS

Saunders, L.B. 1982. Essential nesting habitat of the goshawk (Accipiter gentilis) on the Shasta-Trinity National Forest, McCloud District. M.S. Thesis, California State University, Chico, CA.

7,436 ha of potentially suitable habitat was surveyed for goshawks on the McCloud District of the Shasta-Trinity National Forest. Seven newly discovered and 6 historical nest areas were analyzed.

Mean nest stand canopy closure was 77% (range = 53-92). The majority of nest stands had less than 25% ground cover and 200-300 stems per acre.

Nest sites were similar to nest stands, but had a greater density of large trees and generally higher canopy closure (mean = 81%). Stem density varied with 41% of sites having <200 stems/acre.

Distance to water was highly variable (15-1,700 m, 44-5,576 ft). 75% of nests were at least 100 m from water.

58% of nest were on slopes. 48% were on the lower third or toe of a slope. Five on flat ground, which is very prevalent on the McCloud District.

All nest were in the lower portion of the canopy.

Orientation varied greatly, the largest number facing north-east.

 

SCHWEICH

Schweich, M. 1997. Results of five years of goshawk monitoring on the Modoc National Forest. Modoc National Forest.

Habitat within the 600 PFA on 52 territories with "high quality" surveys over five years (1992-1996) were compared with nesting success. Of the 15 territories with less than 180 acres of "quality habitat" only 8 produced at least one fledgling in five years. Of the 18 territories with 180-348 acres of quality habitat, 16 produced at least one fledgling in five years. Of the 19 territories with more than 348 acres of quality habitat, 17 were successful at least one in five years.

The territories with less than 180 acres of quality habitat had a mean reproductive success rate of 27% while the latter two were 41% and 43% respectively.

 

WOODBRIDGE AND DETRICH

Woodbridge, B. and P. Detrich. 1994. Territory occupancy and habitat patch size of northern goshawks in the southern Cascades of California. Studies in Avian Biology 16:83-87.

  • Territories typically contained 3-9 nest trees. The mean number used was 2.6 (range = 1-5). Forty-four percent of nest trees were also used in the previous year. Forty-nine percent of nest trees were used at least twice in five years.

Distribution of alternate nests was variable. Most were clumped within 2-3 adjacent stands, some were up to 2.1 km away. The mean distance was 273 m. Longer movement may not have been detected.

Territories typically contained 1-5 nest stands, ranging from 4.1 to 115 ha in size. 85% of nest stands were less than .7 km apart.

Individual nest stands were occupied in 46% of years. Stands <10 ha were "occasionally" occupied, while stands >20 ha were occupied in a "high proportion" of years.

Clusters of nest stands ranged from 10.5 to 114 ha in size. Most nest stand clusters were clearly distinct of nest stand clusters in neighboring territories, 18% (5) territories, however, had widely dispersed clusters with less distinct territory boundaries.

The mean occupancy rate of nest stand clusters was 74%. Occupancy of clusters <20 ha was <50%, 40 ha was 75-80%, and >61 ha was nearly 100%. "...patch size may be an important factor determining quality of nesting habitat."

Long-term monitoring did demonstrate a distinction between post-fledging family areas and alternate nest stand.

87% of 84 nesting attempts were successful (i.e. produced a fledgling).

Average productivity was 1.93 young per attempt. There was no relationship between stand size cluster and productivity. The mean number of young per occupied territory was relatively uniform. Nest success and productivity were likely overestimated.

In 23 "traditional" territories where occupancy was predictable, nest clusters were distinct. In the 5 "ephemeral" territories where occupancy was sporadic, nest stands were widely spaced. They were highly fragmented areas of lodgepole and mixed-pine with extensive bark beetle mortality. High prey densities or vulnerabilities may have attracted goshawks to nest in these areas with little mature forest.

Historic logging has caused the study area to contain scatted patches of mature forest within a matrix of thinned and regenerating stands, yet it contains relatively dense goshawk populations. "Goshawk territories, however, were associated with the larger remaining patches of mature forest, and territory occupancy was positively correlated with the size of nesting habitat patches."

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