The Northern Goshawk (Accipiter gentilis) is a secretive forest raptor occupying boreal and temperate forest across the holarctic. The goshawk is considered a sensitive species by the USDA Forest Service and has been petitioned on two occasions for endangered species status. Many national forests utilize the goshawk as a management indicator species. As a result, our Forest Service partners are very interested in the ecology, population structure, and trends of this species within their management domain.
The Intermountain Bird Observatory has studied
the Northern Goshawk off and on for 20 years
We have contributed directly and consulted for a number of forest management plans in Idaho and elsewhere, and have published a number of peer-reviewed scientific journal manuscripts (listed below; a few more are in the works!).
Advancing the core science for the species,
focusing on the breeding and post-breeding ecology
Adult female Northern Goshawk on territory, South Hills, Idaho
Adult female incubating eggs on a nest in an Aspen tree, South Hills
Beldings Ground Squirrel and avian prey remains emphasize the unusual diet of goshawks in the South Hills
Evaluating the population trends for the species
Dead nestling on ground below a nest. Likely predation by avian predator (Great Horned Owl?), South Hills, Idaho.
Purple color band Z3. Color bands are used to identify and track individuals from year to year, without requiring them to be re-trapped.
This individual was banded in the South Hills in 2012 and was found breeding in the Albion Mountains in 2014 and 2015.
Evaluating the response of the species to changes occurring within the forest
(e.g., increased anthropogenic disturbance, climate change, disease outbreaks, timber harvesting)
ATV trail directly beneath Northern Goshawk nest, Sublett Mountains, Idaho.
Adult male goshawk trapped in un-capped water tank (later rescued), Sublett Mountains, Idaho.
This nest tree in a Northern Goshawk territory was harvested for fire wood.
Fire, natural and human caused, poses a threat to historical nesting territories, Black Pine Mountains, Idaho.
Evaluating the genetic health of this species within the forest
and across the western United States
Evaluating threats to this species, with an emphasis on blood parasites
Nestling goshawks covered in black flies, a known vector of the Leucocytozoon blood parasite, South Hills, Idaho.
Blood parasite (leucocytozoon; blob in center of photo) mixed with avian red blood cells, from a Northern Goshawk in the South Hills, Idaho.
Providing educational and training opportunities for students
preparing for a career in wildlife biology
Raptor biologist Rob (right) instructing student researcher Steph (left) on banding technique of this adult female goshawk, South Hills, Idaho, 2014
Student researcher Kenny (left) and forest wildlife biologist Scott banding a goshawk nestling, Sublett Mountains, Idaho, 2015.
Student researcher Michelle holding adult female goshawk for banding, South Hills, Idaho, 2014. Michelle went on to complete her M.S. at Boise State.
Student researcher Carly releasing a large adult female goshawk after banding, measuring, and weighing. Sublett Mountains, Idaho 2017.
Student researcher Lauren rappelling out of a goshawk nest tree. South Hills, Idaho 2016. Photo Credit: Elizabeth Meisman
Goshawk Journal Articles
Miller, R. A. 2017. “Repeated Observations of Northern Goshawks Foraging as Terrestrial Predators”. Journal of Raptor Research 51(4):480-482.
Key findings: We documented the first observations of Northern Goshawks preying on ground squirrels by pursuing them on-foot rather than on-the-wing.
Bechard, M. J., G. D. Fairhurst, and G. S. Kaltenecker. 2006. “Occupancy, Productivity, Turnover and Dispersal of Northern Goshawks in Portions of the Northeastern Great Basin.” Studies in Avian Biology 31: 100–108.
Key findings: Over a 10-year period in southern Idaho, Northern Goshawk productivity was lower and turnover was higher than in other areas where goshawks are studied.
Hasselblad, K., M. J. Bechard, and J. C. Bednarz. 2007. “Male Northern Goshawk Home Ranges in the Great Basin of South-Central Idaho.” Journal of Raptor Research 41: 150–155.
Key findings: Male home range (hunting area) within the South Hills is on average smaller than other places where goshawks are studied, suggesting abundant food availability during the core of the breeding season.
Miller, R. A., J. D. Carlisle, M. J. Bechard, and D. Santini. 2013. “Predicting Nesting Habitat of Northern Goshawks in Mixed Aspen-Lodgepole Pine Forests in a High-Elevation Shrub-Steppe Dominated Landscape.” Open Journal of Ecology 3: 109–115.
Key findings: Within the South Hills, Northern Goshawks tend to nest in gently-sloping, east-facing, non-rugged areas of dense aspen and lodgepole pine forests with low reflectance in green wavelengths. This makes up about 8% of the forest, enabling us to more easily discover new territories.
Miller, R. A., J. D. Carlisle, and M. J. Bechard. 2014. “Effects of Prey Abundance on Breeding Season Diet of Northern Goshawks (Accipiter Gentilis) within an Unusual Prey Landscape.” Journal of Raptor Research 48: 1–12.
Key findings: The South Hills and Albion Mountains lack the usual top prey species for goshawks, tree squirrels. We found that goshawks within the South Hills consume 18.5% birds and 78.7% mammals, dominated by the Belding’s Ground Squirrel (75% of biomass). Beldings Ground Squirrel are thus critical for breeding success, but have different availability due to hibernation and estivation (only above ground for 3 months). This presents unique challenges for the goshawk, an area we continue to study.
Jeffries, M. I., R. A. Miller, M. D. Laskowski, and J. D. Carlisle. 2015. High Prevalence of Leucocytozoon Parasites in Nestling Northern Goshawks (Accipiter gentilis) in the Northern Great Basin USA. Journal of Raptor Research 49: 294-302.
Key findings: 100% of the nestlings tested (28 individuals from 12 nests), were infected by Leucocytozoon blood parasites. The intensity of infection was slightly higher for goshawks nesting in Aspen versus those nesting in Lodgepole Pine. We believe these infections pose an additive threat to individuals under stress from other factors, but are not killing them outright.