News & Features

Northern Goshawk: Reports Needed for “the Ultimate Forest Raptor”

Odin, a study subject of PA goshawk research and oldest known goshawk in state. By David Brinker.

On behalf of the Pennsylvania Goshawk Project, which is run by a subcommittee of the Ornithological Technical Committee (OTC) of the Pennsylvania Biological Survey (PABS), we invite birders to contribute goshawk sightings to our research and conservation efforts. The Game Commission is cooperating with this project and protecting goshawk nests on its properties. The Northern Goshawk is one of the rarest nesting raptors in the state and a notably elusive and secretive species. It is a flagship species of the big woods and the wildest parts of the state, sometimes called the “ultimate forest raptor” due to its size, wildness, and fierceness. So, we always wish for more information about the goshawk nests and territories. It currently is considered “Near Threatened” in the state. The state’s birders have contributed a great deal to our knowledge of Northern Goshawk primarily through their reports to the two breeding bird atlas projects and privately to agency staff. The maps of the two Atlas projects, separated by 25 years, seem to indicate that there is a smaller nesting population occupying less of the state than previously. For more information about the PABS goshawk committee’s research, visit www.pabiologicalsurvey.org/goshawk. There you can find images and audio to aid identification as well as forms, instructions, and contact information. Goshawk reports can be e-mailed to goshawk@psu.edu. Any goshawk observations during the breeding season, from late March to June, on game lands should be sent to pgcgoshawk@pa.gov. Reports to either the Pennsylvania Goshawk Project or the Game Commission will be treated as confidential.

The Northern Goshawk is a large accipiter hawk that nests in the forests of North America, Europe, and Asia. They nest in large forest tracts in Pennsylvania, mostly at higher elevations. Goshawks begin nesting in March through May and may be active when you are doing your spring migration birding or spring gobbler hunting. We have often called the goshawk the “ultimate forest raptor” because of its size and fierceness as a forest predator. Goshawks have a varied diet that includes large birds like turkey, grouse, crows, and woodpeckers as well as medium-sized birds like jays, doves, and robins as well as squirrels, rabbits, hares, and rodents of all sizes. They are not specialists by any means and are quite opportunistic about their prey choice. This raptor is one of the most sensitive to disturbance by humans at the nest and represents interior forests as well as any bird species in the state.

Northern Goshawk female at nest contributed by Steve Hoffman, Montana Audubon.

History of Goshawks in Pennsylvania

The Northern Goshawk always has been considered a rare species in Pennsylvania. In the 19th and early 20th century, persecution of goshawks was popular due to their reputation as killers of game and domestic fowl. In the late 1930s the Pennsylvania Game News Magazine published an article by W. M. Dippold entitled “Hunting Goshawks” that detailed ways to find this secretive forest-nesting raptor for shooting. This persecution, including bounties, was popular with hunters and farmers, but wildlife biologists such as Aldo Leopold, Richard Gerstell, and Roger Latham doubted that bounties were effective or necessary. The $5 Pennsylvania bounty for goshawk was removed in 1951, but only after this persecution had a negative impact on goshawks throughout the state. This bounty included fall and winter birds so many non-breeding goshawks also were killed for bounties. Persecution declined even more when goshawks were afforded federal protection by the Migratory Bird Treaty Act in 1972. In more recent times, human development and activities encroaching into the wild forests have been a more likely disturbance of nests and indirect cause of local extirpation of shy nesting goshawks than direct persecution. Goshawks have always suffered more at the hands of humans than the other way around.

Dr. Witmer Stone, ornithologist of the Academy of Natural Sciences in Pennsylvania studying specimens in its collection.

In 1897, Hermann and Otto Behr found a goshawk nest near Lopez on Dutch Mountain and sent the nest with eggs for inclusion in the Academy of Natural Sciences in Philadelphia’s museum collection and reported this rarity to the ornithologist Dr. Witmer Stone as the first goshawk nest documented in the state. This area is near the popular Ricketts Glen State Park and the largely forested State Game Lands 13, 57, and 66. This discovery led to a long friendship between the Behr brothers and Witmer Stone and publication by Dr. Stone on the birds of that area. Early in the 20th century, other ornithologists such as B. H. Warren, R. B. Simpson, and the agency’s state ornithologist George M. Sutton found nesting goshawks in remote great northern forests.

Goshawks have been protected by the Game Commission and USFWS for many years.

The Atlas of Breeding Birds in Pennsylvania (1983 – 89), coordinated by Dan Brauning who is now with the agency, was a big breakthrough for goshawk research. Almost coincidently, Tim Kimmel studied goshawk status and habitat requirements as a graduate student at Penn State under the direction of Professor Richard Yahner from 1988 – 92. He enlisted students, falconers, and bird watchers to evaluate the nesting habitat and its availability for 63 sites in the state where goshawks were confirmed nesting sometime between 1974 and 1989. Although the Kimmel team collected data in several counties the focus was in Allegheny National Forest in the Northwestern region and Bald Eagle State Forest of the Northcentral region. The research included testing methods for surveying nesting goshawks and guidelines for protecting nests. Kimmel and Yahner published their findings in a variety of venues including as a report to the Pennsylvania Wild Resource Fund that supported the study. Kimmel continued some studies of goshawks after he left Penn State and his research results continue to inform us about goshawks.

The comparison map of Northern Goshawk distribution for the 2nd Atlas of Breeding Birds in Pennsylvania (Penn State Press, 2012, Wilson, Brauning, Mulvihill, editors) compared to the 1st Atlas distribution. For more information see: http://www.pabirdatlas.psu.edu/

David Brinker, a raptor biologist based in Maryland, has been studying goshawks since 1978, first in Wisconsin, but most recently in the Central Appalachians especially in Pennsylvania’s northwestern counties including Allegheny National Forest. There he gets the cooperation of its staff and a band of loyal assistants. The Brinker study has looked at nest site fidelity, productivity, demography, and resident status. One of the findings is that most goshawks are non-migratory residents that expand their foraging area in the winter to areas near their nesting territories. He also has found that goshawk nest success varies greatly from year to year, but many territories are occupied consistently over time. Brinker like everyone who has studied the elusive goshawk has called for more research and conservation effort for this woodland raptor. The Game Commission and others continue to cooperate with the research conducted by Brinker and others in the state.

A follow-up of the first atlas, a Second Atlas of Breeding Birds in Pennsylvania was conducted with great contribution of the state’s birders from 2004 to 2009. This second Atlas, coordinated by Bob Mulvihill of the Powdermill Nature Preserve, benefited from lessons learned in the first Atlas and attracted a cadre of birders who had gained experience with rare and difficult-to-find species through that and other citizen science projects. Rare species like goshawk were targeted for searches. So, it was disappointing that fewer goshawks were found in this second Atlas and in a smaller breeding range. Few goshawks were found south of Route 80 and east of the Northeast extension of the Turnpike. The breeding range of this forest raptor seems to have contracted to the core forest of the central and northern counties on the plateaus.  There also has been an apparent decline in New York as documented by its second breeding bird atlas project. Goshawks have nearly disappeared as a breeding species from the Appalachian Mountains in Maryland and Virginia.  One of the questions being posed by researchers is whether this range contraction is real or a result of less coverage and reporting of an elusive bird that often lives in more remote parts of the forest.

Northern Goshawk adult, contributed by Steve Hoffman of Montana Audubon.

Goshawk Nesting

Goshawk nests are large stick constructions, often in a large tree, but can be difficult to see through the leaf and needle cover in the expansive canopy where they are built. It is sometimes necessary to walk from tree to tree and check out the upper limbs of each one to find a nest. They can betray their presence with plucking perches and “kill stumps” including logs where they pluck or dismember their prey. Finding a pile of feathers and fur could be an important clue to the presence of goshawks nesting nearby. Goshawks demonstrate remarkable site fidelity and persist for many years at locations with good habitat and prey populations. They often nest within a few hundred feet of a previous nest in the same tree stand. Although they can aggressively defend their nests, goshawks are very secretive and difficult to detect during the nesting season. It is very helpful to start searches early in the morning and to know their vocalizations. Many of my observations have depended on hearing their loud, rhythmic “kak” alarm calling or the wail call. They can be confused with the sounds made by other hawks and large woodpeckers, so it is good to study and become familiar with their vocalizations.

Northern Goshawk nest in Allegheny National Forest by Scott Stoleson.

Goshawk Status and Conservation in Pennsylvania

The Northern Goshawk is now considered a “Near Threatened” species by the Ornithological Technical Committee, a small step from “Threatened” due to its reduced population and apparently smaller breeding range. It has never been a common species in the state and mostly confined to the larger forest blocks like the Allegheny National Forest, the Black Forest of the Northcentral region, North Mountain, the Seven Mountains region, and the Pocono Mountains. During the first Breeding Bird Atlas in the 1980s there were some reports along the Kittatinny Ridge and other forested areas in the southern counties. And, there were several more goshawks reported during the first Atlas in the Pocono region than during the second Atlas. Basically, in the second Atlas there were few reports south of U.S. Route 80 and east of Route 81. Do these differences reflect a real change in goshawk population and range or just a lack of reports of an elusive species in some parts of the state with less coverage by birders in the deep woods? Falconers will rarely reveal the location of a nest that they have worked hard to find for their own source of goshawk nestlings and the birders that know of a goshawk nest consider it confidential information to avoid disturbance of the birds. So, it is a challenge for researchers and conservationists to obtain the nest site information necessary to study the birds and to protect them. We need to overcome these challenges to have a chance with goshawk conservation in our state. Other states in the Northeast and the Central Appalachians also have reported some declines in goshawks and some range retractions.

Northern Goshawk up close by Jake Dingel

One of the pertinent questions for anyone interested in Northern Goshawks is “what are the limiting factors for this raptor in the state?” Or, why are there not more goshawks nesting in more areas than currently known? A partial list of possible reasons for goshawk territory abandonment and range contraction includes: 1. forest fragmentation, 2. human development (residential, energy, road-building), 3. timbering activities, 4. tree pests and diseases (e.g. hemlock woolly adelgid, gypsy moth infestations), 5. West Nile virus and other diseases, 6. nest predation increase (fishers, Great Horned Owls), 7. human disturbance (hikers, vehicles, falconers, birders, photographers), 8. winter and spring weather patterns (snow & ice cover, precipitation totals), 9. falconer take of nestlings, 10. direct persecution of goshawks (shooting, nest destruction). Some of these potential factors certainly overlap. By gathering more information about goshawk nesting territories past and present, we may be able to discern which are the most important factors influencing goshawk populations and where efforts to conserve them can be concentrated.

A Pennsylvania goshawk nest in a Red Maple surrounded by conifer evergreens. By Doug Gross

Reporting Goshawk Sightings

Any report sent in to the PABS goshawk page (the “Pennsylvania Goshawk Project”) or the Game Commission Wildlife Diversity goshawk e-mail account will be kept confidential. The driving force behind this effort is that we cannot protect a goshawk nest if we do not know precisely where it is. We suspect that goshawk nests are lost simply from human interference or nesting habitat destruction that could be prevented with seasonal or permanent protections of the location, especially on government property. The members of the Pennsylvania Goshawk Project are listed on the PABS goshawk website. This committee includes researchers, birders, government agency biologists, and falconers interested in goshawk research and conservation. Pennsylvania State University, Allegheny National Forest, Hawk Mountain Sanctuary, Pennsylvania Society for Ornithology, the Pennsylvania Hawk and Migration Trust, the Pennsylvania Department of Conservation and Natural Resources, and the Game Commission have joined together through the OTC in this effort. And, the Game Commission has a responsibility to manage for those species that are rare and declining in the state such as the Northern Goshawk. It is one of the Species of Greatest Conservation Need listed as a priority for management and conservation in the Pennsylvania Wildlife Action Plan.  For more information about the SWAP, please see the Pennsylvania Game Commission’s pages on that report: http://www.pgc.pa.gov/Wildlife/WildlifeActionPlan/Pages/default.aspx

An adult goshawk being held for banding as part of Pennsylvania research project. Contributed by Scott Stoleson.

Any report about goshawk breeding activity or nesting should include details about the precise location and the coordinates of the observation. In the “old days” much goshawk research was done with map and compass without the advantage of modern technology. Now it is much easier. With GPS units and smartphones with geolocation applications (like Google Maps), there should be adequate means to document the necessary information about the sighting. Describing the location, the name of a road or trail, and any local landmarks are helpful to locate a rare bird. It is helpful to use the convenient Atlas breeding codes, but describing what you saw in terms of field marks for identification and behavior to determine breeding status. Photographic images are also helpful even of the location.

Since Northern Goshawk is a sensitive species, making reports through eBird is a bit challenging. Care should be taken to revealing a nest area that could lead to disturbance to goshawk nesting areas by curious visitors or those that might wish harm to goshawks or their nests. One strategy is to delay reporting a field trip with a sensitive species until after the breeding season or be very vague about the location (a large-scale “hotspot”). Another strategy is to hide the information on that species, an option given on the right hand side of the data entry page. The primary message in this article is for birders to cooperate with the goshawk researchers. For information about reporting sensitive species like goshawk, please see the Help page on the subject: http://help.ebird.org/customer/en/portal/articles/1006789-guidelines-for-reporting-sensitive-species

A Northern Goshawk adult near nest in Pennsylvania by Wayne Laubscher.

How to Help the Goshawk Research and Conservation

Goshawk reports can be e-mailed to goshawk@psu.edu or by postal mail to Goshawks C/o Dr. Margaret Brittingham, Ornithological Technical Committee, Wildlife Resources, 409 Forest Res. Bldg., Penn State University, State College, PA 16802 ; phone reports to Laurie Goodrich of the Hawk Mountain Sanctuary at: 570-943-3411×106. Website: www.pabiologicalsurvey.org/goshawk. And, goshawk observations on state game lands or where there may be protection issues should be sent to pgcgoshawk@pa.gov.

Doug Gross, Endangered and Non-game Bird Section Supervisor; Pennsylvania Game Commission, dogross@pa.gov