Golden Gate Raptor Observatory
Encyclopedia
The Golden Gate Raptor Observatory (GGRO) is a non-profit organization whose mission is to study migrating birds of prey along the Pacific coast and to inspire the preservation of raptor
populations in California. Established in 1985, it is a joint program of the Golden Gate National Parks Conservancy
and National Park Service
, and is located in the Marin Headlands
, just north of San Francisco, California
.
The GGRO programs center around Hawk Hill
, one of the highest points (940 feet elev.) immediately above the Golden Gate
on the north side, in Marin County. Discovered as the most productive hawk migration site in California by ornithologist Laurence Binford in 1972, Hawk Hill was called Point Diablo early on. This publicly-accessible site, a centerpoint of the Golden Gate National Recreation Area
, offers visitors a spectacular vista of the San Francisco Bay Area, as well as the best view of the autumn hawk migration. At the migration's peak in late September/early October, as many as 800 raptors a day maybe counted overhead.
The Golden Gate migration is primarily one of diurnal raptors — hawks
, kites, falcons
, eagles
, vultures
, osprey
, and harriers — with nineteen falconiform species appearing annually. In addition, a small range of non-raptorial migrants appear over the Marin Headlands in the autumn; this includes three species of swift
, six species of swallow
, and Band-tailed Pigeons
, among dozens of avian species.
The GGRO is one of the few bird research stations in the country where a raptor-counting program and a raptor-banding program operate in the same organization. Started by National Park Service
biologist Judd A. Howell, and volunteers S. Williston Shor and Carter L. Faust in the early 1980s, the Raptor Observatory today still operates under the philosophy that incorporating citizens into the process of gathering scientific data will deepen long-term conservation results. Consequently, the organization’s small staff is augmented by the work of 280+ highly trained volunteers, coming from all different disciplines. The GGRO publishes an annual report, contributes annual results to national databases, and collaborates on various research projects with local universities.
, and radio-tracking (Telemetry).
While on migration, birds of prey use air movements, such as rising thermals and updrafts on wind-facing hills, to maintain their altitude. A preference for flying over land keeps many hawks from readily flying over open water.
Moving toward the Marin peninsula's southern tip in the Headlands, the "front" of migrating raptors is squeezed by San Francisco Bay
on the east and the Pacific Ocean
on the west. Many end up flying over Hawk Hill as they negotiate the two-mile gap to San Francisco.
Bird of prey
Birds of prey are birds that hunt for food primarily on the wing, using their keen senses, especially vision. They are defined as birds that primarily hunt vertebrates, including other birds. Their talons and beaks tend to be relatively large, powerful and adapted for tearing and/or piercing flesh....
populations in California. Established in 1985, it is a joint program of the Golden Gate National Parks Conservancy
Golden Gate National Parks Conservancy
Established in 1981, the Golden Gate National Parks Conservancy is the nonprofit partner that supports and assists the Golden Gate National Parks in research, interpretation, and conservation programs....
and National Park Service
National Park Service
The National Park Service is the U.S. federal agency that manages all national parks, many national monuments, and other conservation and historical properties with various title designations...
, and is located in the Marin Headlands
Marin Headlands
The Marin Headlands is a hilly area at the southernmost end of Marin County, California, just north of the Golden Gate Bridge. The Headlands are located just north of San Francisco, immediately across the Golden Gate Bridge. The entire area is part of the Golden Gate National Recreation Area...
, just north of San Francisco, California
San Francisco, California
San Francisco , officially the City and County of San Francisco, is the financial, cultural, and transportation center of the San Francisco Bay Area, a region of 7.15 million people which includes San Jose and Oakland...
.
The GGRO programs center around Hawk Hill
Hawk Hill, California
Hawk Hill is a peak in the Marin Headlands, just north of the Golden Gate Bridge and across the Golden Gate strait from San Francisco, California. The hill is within the Golden Gate National Recreation Area....
, one of the highest points (940 feet elev.) immediately above the Golden Gate
Golden Gate
The Golden Gate is the North American strait connecting San Francisco Bay to the Pacific Ocean. Since 1937 it has been spanned by the Golden Gate Bridge...
on the north side, in Marin County. Discovered as the most productive hawk migration site in California by ornithologist Laurence Binford in 1972, Hawk Hill was called Point Diablo early on. This publicly-accessible site, a centerpoint of the Golden Gate National Recreation Area
Golden Gate National Recreation Area
The Golden Gate National Recreation Area is a U.S. National Recreation Area administered by the National Park Service that surrounds the San Francisco Bay area. It is one of the most visited units of the National Park system in the United States, with over 13 million visitors a year...
, offers visitors a spectacular vista of the San Francisco Bay Area, as well as the best view of the autumn hawk migration. At the migration's peak in late September/early October, as many as 800 raptors a day maybe counted overhead.
The Golden Gate migration is primarily one of diurnal raptors — hawks
Hawk
The term hawk can be used in several ways:* In strict usage in Australia and Africa, to mean any of the species in the subfamily Accipitrinae, which comprises the genera Accipiter, Micronisus, Melierax, Urotriorchis and Megatriorchis. The large and widespread Accipiter genus includes goshawks,...
, kites, falcons
Falcon
A falcon is any species of raptor in the genus Falco. The genus contains 37 species, widely distributed throughout Europe, Asia, and North America....
, eagles
Eagle
Eagles are members of the bird family Accipitridae, and belong to several genera which are not necessarily closely related to each other. Most of the more than 60 species occur in Eurasia and Africa. Outside this area, just two species can be found in the United States and Canada, nine more in...
, vultures
Turkey Vulture
The Turkey Vulture is a bird found throughout most of the Americas. It is also known in some North American regions as the Turkey Buzzard , and in some areas of the Caribbean as the John Crow or Carrion Crow...
, osprey
Osprey
The Osprey , sometimes known as the sea hawk or fish eagle, is a diurnal, fish-eating bird of prey. It is a large raptor, reaching more than in length and across the wings...
, and harriers — with nineteen falconiform species appearing annually. In addition, a small range of non-raptorial migrants appear over the Marin Headlands in the autumn; this includes three species of swift
Swift
The swifts are a family, Apodidae, of highly aerial birds. They are superficially similar to swallows, but are actually not closely related to passerine species at all; swifts are in the separate order Apodiformes, which they share with hummingbirds...
, six species of swallow
Swallow
The swallows and martins are a group of passerine birds in the family Hirundinidae which are characterised by their adaptation to aerial feeding...
, and Band-tailed Pigeons
Band-tailed Pigeon
The Band-tailed Pigeon, Patagioenas fasciata, is a medium-sized bird of the Americas. Its closest relatives are the Chilean Pigeon and the Ring-tailed Pigeon, which form a clade of Patagioenas with a terminal tail band and iridescent plumage on their necks.It ranges from British Columbia, Utah, and...
, among dozens of avian species.
The GGRO is one of the few bird research stations in the country where a raptor-counting program and a raptor-banding program operate in the same organization. Started by National Park Service
National Park Service
The National Park Service is the U.S. federal agency that manages all national parks, many national monuments, and other conservation and historical properties with various title designations...
biologist Judd A. Howell, and volunteers S. Williston Shor and Carter L. Faust in the early 1980s, the Raptor Observatory today still operates under the philosophy that incorporating citizens into the process of gathering scientific data will deepen long-term conservation results. Consequently, the organization’s small staff is augmented by the work of 280+ highly trained volunteers, coming from all different disciplines. The GGRO publishes an annual report, contributes annual results to national databases, and collaborates on various research projects with local universities.
Programs
The GGRO has three ways of monitoring the fall migration of raptors: hawk counting (Hawkwatch), hawk bandingBird ringing
Bird ringing or bird banding is a technique used in the study of wild birds, by attaching a small, individually numbered, metal or plastic tag to their legs or wings, so that various aspects of the bird's life can be studied by the ability to re-find the same individual later...
, and radio-tracking (Telemetry).
- Hawkwatch involves a hawk count from the top of Hawk Hill. Volunteers identify and count the 19 species of raptors that pass through.
- The banding program involves trapping, banding, measuring and then releasing hawks from various blinds located throughout the Marin Headlands.
- Telemetrists attach a tiny radio transmitter to a tail feather of a hawk and then follow the hawk on its migration by triangulating signals from the transmitter.
Migration Site
The Marin Headlands are a raptor migration thoroughfare. Many raptors migrate south from their northern or higher altitude nesting areas to find better sources of prey during fall and winter.While on migration, birds of prey use air movements, such as rising thermals and updrafts on wind-facing hills, to maintain their altitude. A preference for flying over land keeps many hawks from readily flying over open water.
Moving toward the Marin peninsula's southern tip in the Headlands, the "front" of migrating raptors is squeezed by San Francisco Bay
San Francisco Bay
San Francisco Bay is a shallow, productive estuary through which water draining from approximately forty percent of California, flowing in the Sacramento and San Joaquin rivers from the Sierra Nevada mountains, enters the Pacific Ocean...
on the east and the Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
on the west. Many end up flying over Hawk Hill as they negotiate the two-mile gap to San Francisco.