Northern Goshawk (Accipiter gentilis) Potential Occurrence: Nesting Unlikely to Occur



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Aves (Birds): Ciconiiformes, Accipitridae

Northern Goshawk (Accipiter gentilis)

Potential Occurrence: Nesting Unlikely to Occur



Status: (Nesting)

Federal: None

State: Species of Special Concern

Other: MBTA



Species Description:

C
Photo: © Steve Byland


onspicuous eyebrow, flaring behind eye, separates adult's dark crown from blue-gray back. Underparts are white with dense gray barring appear gray at distance; has wedge-shaped tail with fluffy undertail coverts. Juvenile is brown above, buffy below, with thick blackish brown streaks, heaviest on flanks; tail has wavy dark bands bordered with white and a thin white tip; undertail coverts usually have dark streaks. In flight, note tawny bar on upperwing on greater secondary coverts. (From Dunn and Alderfer 2006)

Distribution:

Holarctic distribution (Brown and Amadon 1968, Squires and Reynolds 1997). Current breeding and distributional records indicates that Northern Goshawks are still well distributed across their core breeding range in most of the northern Coast Ranges, the Klamath and Siskiyou moun­tains, across the Cascades, Modoc Plateau, and Warner Mountains, and south through the Sierra Nevada. Records and additional fieldwork have extended the known range (likely mostly occupied prior to 1944) south to southern Mendocino County in the Coast Ranges, south past the Sierra Nevada to the Tehachapi Mountains, east to the Glass Mountain region and White-Inyo ranges, and sparsely south to the Mount Pinos–Frazier Mountain area and the San Gabriel, San Bernardino, San Jacinto, and Cuyamaca mountains of southern California (Garrett and Dunn 1981, Bloom et al. 1986, Lentz 1993, Kiff and Paulson 1997, J. Keane and B. Woodbridge unpubl. data). (From Shuford and Gardali 2008)

In California, Goshawks breed in the North Coast and Sierra Nevada Ranges, and in the Klamath, Cascade and Warner mountains (Zeiner et al. 1990). In breeding areas, they are scarce to uncommon yearlong residents, preferring middle to high elevation dense mature coniferous forests. During the winter they are casual visitors along the coast, throughout the foothills, and in northern deserts where they are associated with pinyon (Pinus spp.) -juniper (Juniperus spp.) and low-elevation riparian habitats (Zeiner et al. 1990).

Life History & Threats:

Goshawks are opportunistic predators taking at least 44 species of forest birds and mammals in western North America (Reynolds et al. 1992). At least 36 species of prey are consumed in California (Schnell 1958; Bloom et al. 1986). Prey are caught in the air, on the ground, or in vegetation. An adult goshawk requires approximately 119-150 gm (4.2-5.3 oz) of food per day, or the equivalent of one or two small birds per day (Brown and Amadon 1968). A study of prey remains found in territories surrounding California goshawk nests identified 234 prey items representing 31 species (Bloom et al. 1986). By frequency, avian prey constituted 68% of the total with mammals accounting for the remaining 32%. (From Timossi et al. 1995)



Habitat & Habitat Associations:

General Habitat: The northern goshawk (Accipiter gentilis) inhabits coniferous or mixed coniferous forests in western North America (Wattel 1981; American Ornithologists' Union 1983). Uses mature and old-growth stands of conifer and deciduous forested habitats. Dense, mature conifer and deciduous forest, interspersed with meadows, other openings, and riparian areas required (Polite and Pratt 2005).

Foraging Habitat:

Goshawks forage in mature dense forests, along forest edges, and in clearings (Bent 1937; Bartelt 1977; Hennessy 1978; Jones 1979). In California, meadows, riparian corridors, and aspen groves are critical habitat for the key prey species taken by goshawks (Bloom et al. 1986). Goshawks have been observed foraging in a wide variety of forest types and conditions (Fischer 1986; Kenward and Widen 1989; Widen 1989) suggesting that foraging habitat may be as closely tied to prey availability as to habitat composition or structure (Kenward and Widen 1989; Reynolds 1989). (From Timossi et al. 1995)



Nesting Habitat:

Nesting habitat includes north-facing slopes near water (Polite and Pratt 2005).

The availability of open water is an important factor in goshawk nest site selection (Brown and Amadon 1968; Bartelt 1977; Hennessy 1978; Shuster 1980; Reynolds et al. 1982). In California, goshawk nests ranged from 15-1700 m (44-5,576 ft) from water with 75% of the nests located more than 100 m (328 ft) from water (Saunders 1982). In northwestern California, nests ranged from 0-357 m (0-1,171 ft) from water (Hall 1984). (From Timossi et al. 1995)

Nest site limits often coincide with boundaries between stands of different age or species composition, or with topographic features such as ridgelines (Reynolds 1983). Goshawks nest in older stands of coniferous, mixed, or deciduous forest characterized by large trees, dense canopies, and northerly aspects in the southern portion of the hawks' range ( Bartelt 1977; McGowan 1975; Hennessy 1978; Shuster 1980; Reynolds et al. 1982; Saunders 1982; Hall 1984; Hayward and Escano 1989). The elevational range of nesting goshawks varies in northwestern California from 834-1186 m (2,736-3,891 ft) (Hall 1984). Goshawk nest sites are characterized by a high percentage of canopy cover with estimates ranging from 40-89% (Schnell 1958; Hennessy 1978; Moore 1980; Shuster 1980; Hall 1984; Crocker-Bedford and Chaney 1988; Hayward and Escano 1989). In northwestern California, Hall (1984) found a mean canopy closure of 94%. (From Timossi et al. 1995)



Conceptual Basis for GIS Model Development: To identify potential habitat for Northern Goshawk in the Study Area, we mapped:

Foraging and Nesting Habitat:

  • coniferous forest (i.e., Redwood-Douglas fir mix (Sequoia sempervirens-Pseudotsuga menziesii) and Pacific Douglas fir (Pseudotsuga menziesii var.menziesii))



  • broadleaf upland forest and cismontane woodland (both of which include mixed hardwoods, montane mixed hardwoods, and single dominant hardwoods)

Possible best foraging habitat:

  • trees > 61 cm DBH

  • closed/high density forest (>70% canopy cover)

  • edges of forest and woodlands

  • riparian corridors - mapped as bare ground (which in the study area occurs only along the exposed banks of Rancheria Creek) and riparian vegetation. Riparian vegetation in the Study is patchy and is not represented well in existing GIS maps. To estimate riparian vegetation cover, we use a 130 m buffer surrounding Rancheria Creek.)

    • For mapping purposes this was interpreted to mean that all areas within the study area considered to be riparian corridors are potential best foraging habitat for this species. As such, the riparian layer was not clipped by the extent of the conifer and cismontane forests.

Possible best nesting habitat was mapped as areas with:

  • trees > 61 cm DBH

  • closed/high density forest (>70% canopy cover)

Potential Occurrence in the Galbreath Wildlands Preserve: Protection status for this species applies to nesting individuals.

Habitat: Potential nesting habitat, areas with mature, densely canopied forests and woodlands, occurs in roughly a dozen areas throughout the Preserve (Figure 70). The largest of these is located in coniferous forest in the northeastern corner of the Preserve.

Appropriate habitat shown in the GIS map overestimates potential nesting habitat for this species because it does not incorporate information on the distance to open water. In northwestern California, the maximum distance that Goshawks have been found nesting from open water is 375 m (~1/4 mile). The surface waters of Rancheria Creek generally recede early in the year and do not provide open water throughout the nesting period. Perennial areas of the mainstem of Rancheria Creek and the Navarro River are well over ¼ mile from the Preserve.

To the extent that prey availability can be tied to habitat structure, potential foraging habitat (needed to support the feeding of young) quality is moderate in the Study Area. Abundance is low on the Preserve: adjacent properties to the Preserve have a greater availability of forest edges and could provide more extensive foraging habitat. Within the Preserve, riparian areas occur in small irregular patches along the river.

Due to the lack of open water, significant riparian vegetation, and relatively low abundance of forest edges on the Preserve, we estimate that the quality of nesting habitat for this species is poor.



Nearest Occurrence:

Documented Occurrences in the Galbreath Wildlands Preserve: This species has not been documented on the Preserve. To our knowledge no surveys have been conducted.

Nearest Occurrence to the Galbreath Wildlands Preserve: This species has been reported to occur in the Ornbaun Valley USGS quad adjacent to the Preserve.

Summary: Nesting Goshawks are “Unlikely to Occur” in the Preserve due to the lack of open surface water throughout the nesting season, and the low abundance of quality foraging habitat in the Preserve. .

References

Byland S. Northern Goshawk Photograph. Smithsonian National Zoological Park – Migratory Bird Center. . 2010 September 29.

Dunn J, Alderfer J. 2006. Field Guide to The Birds of North America. 5th Edition. Washington, D.C.: National Geographic. pg. 126.

Polite C, Pratt J. 2005. Northern Goshhawk. California Wildlife Habitat Relationships System, California Department of Fish and Game, California Interacgency Wildlife Task Group. . 2010 June 26.

Shuford, W. D., and Gardali, T., editors. 2008. California Bird Species of Special Concern: A ranked assessment of species, subspecies, and distinct populations of birds of immediate conservation concern in California. Studies of Western Birds 1. Western Field Ornithologists, Camarillo, California, and California Department of Fish and Game, Sacramento.

Timossi I, Woodard E, Barrett R. Habitat suitability models for use with ARC/IN FO: Northern goshawk. Calif. Dept. of Fish and Game, CWHR Program , Sacramento, CA . CWHR Tech. Report No. 14.



Species Account Description: Neal Ramus & Emily Harvey

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