Introduction: Return of the Peregrine

Many a traveler across Portland's Fremont Bridge has been distracted and delighted by the sight of a peregrine falcon perched atop a lamppost or slicing through the air at over 200 miles per hour taking aim at an unsuspecting rock dove (pigeon). For many it is has become a part of their daily commute. However it is not a sight that any of us should take for granted.

Widespread use of the pesticide DDT during the 1940's, 50's and 60's caused peregrines and other top of the food chain predators such as bald eagles and osprey to lay eggs with thin eggshells. The eggs would break during incubation leading eventually to a crash in the population. By 1970 the American peregrine falcon (Falco peregrinus anatum) was almost completely extirpated from the Continental United States. There were no known nest sites east of the Mississippi River and only a handful in the Western United States. Peregrine populations in Oregon were completely decimated; by 1970 there were no peregrine falcons known to be nesting anywhere in the state.

The listing of the American peregrine falcon under the Federal Endangered Species Act and the banning of DDT, both in 1972, were the first steps on the long road to recovery. Natural restoration of populations was augmented by an intensive captive rearing and release program, the largest effort of its kind ever undertaken. Captive raised peregrines were released on Mt. Hood and at several locations in the Columbia River Gorge. In 1980, the restoration effort began to pay off; peregrines were discovered nesting at Crater Lake.

Peregrines first began appearing on Portland's urban landscape in the late 1980's. A pair took up temporary residence on the Lloyd Center Towers. Attempts to induce nesting were undertaken by the placement of nest boxes on the buildings. However no nesting attempts were documented and the pair eventually disappeared.

In 1993 a new pair of falcons was sighted regularly on Portland's Fremont Bridge, but again no nesting occurred. The pair did remain near the bridge throughout the summer and the ensuing fall and winter. In April of 1994, biologists finally observed the moment that they had been awaiting. The pair was observed entering and departing a platform under the lower deck on the east end of the bridge, a clear indication that they were incubating eggs!

Urban Peregrines

Records of peregrine falcons nesting on human-made structures date back to the Middle Ages when they were discovered nesting on the towers of cathedrals. While the prevalence of this fiercest and fastest of predators on human made structures may at first seem surprising, in fact bridges and skyscrapers have many of the specific attributes sought by peregrines when selecting nest sites.

Peregrine falcons do not build stick nests. Instead they nest on high inaccessible cliff ledges, hollowing out an area of sand and gravel known as a "scrape." Peregrine nests are typically located in close proximity to water. They prey primarily on other bird species. Although they are not terribly large birds (females are about the size of a raven and males are about the size of a crow), they have been documented taking species ranging in size from hummingbirds to Aleutian Canada geese. Their primary hunting strategy is to climb high in the sky and then drop in dives (known as "stoops") clocked at over 200 miles an hour. Although they are not terribly fast fliers off the mark, the speeds attained in dives make the peregrine the fastest known vertebrate species on earth. Prey is often killed on contact.

Urban bridges and skyscrapers with their high, inaccessible ledges and abundant populations of rock doves and starlings meet many of the peregrine's nesting needs. Since the recovery began, peregrines have established nest sites in cities across the United States. At one time New York City has the highest density of nesting peregrines known anywhere in the world.

Urban sites also come with hazards not associated with cliff sites. Peregrines are highly sensitive to nest disturbance. News helicopters, bridge and building maintenance activities, proximal construction projects and even just ordinary human activity near the nest site can cause nest failure. Bridges are particularly hazardous for nesting peregrines because young falcons tend to fledge (leave the nest) prior to the time they are able to fly. The air currents associated with cliffs tend to rise in updrafts that keep young falcons on the nest ledge as they flap their wings and build up strength for their first flights. Conversely, many bridges have downdrafts and small, isolated ledges that allow young falcons only a minimum of movement. When they do fall, the first step is usually a plunge to the ground or water below.

Fremont Bridge Peregrine Watch: Protecting Portland's Peregrine Falcons

The appearance of peregrines on Portland's Fremont Bridge was viewed initially as a mixed blessing. Biologists anticipated that the nesting falcons would provide the public with a tremendous opportunity to view this recovering species. However they also expected that the survival rate of fledglings at the site would be low. It was considered to be a "sacrifice site," one that would be of great educational value but one that would not contribute to the gene pool. A collaborative effort between the Audubon Society of Portland and the Oregon Department of Fish and Wildlife has proven that in fact this site could achieve both objectives.

Audubon Society of Portland first became involved with the Fremont Bridge peregrines in 1994. A single youngster fledged from the site that year and although she survived her initial flight, she slammed into the window of a Rolls Royce dealership on Burnside a few days later. She was transported to the Audubon Society of Portland Wildlife Care Center where she was treated for her injuries. A month later she was released back to the care of her parents at the bridge. She was seen hunting and flying around the Fremont in subsequent months and to the best of our knowledge is still flying free.

In 1996, Audubon and ODFW initiated what was to become known as the Portland Peregrine Watch Program. Trained volunteers were stationed under the bridge to provide monitoring, protection and educational outreach. During its first season, Peregrine Watch attracted over 3,000 people who came down to see and learn about peregrines.

Volunteers provide valuable data to biologists regarding the behavior of urban peregrines and also determine a specific nesting chronology. This information allows biologists to enter the nest at a specific time during the nesting cycle when the young are old enough to thermoregulate, but still young enough that they are not yet mobile and capable of jumping off the ledge. During nest entry, young peregrines are banded, eggs shell fragments and prey remains are collected, blood samples are taken and the overall health of the chicks is assessed.

Perhaps most importantly, a cadre of super dedicated volunteers provided protection for the nest site. During the early part of the season, this involved preventing disturbance of the nesting falcons. For those who remember when the local television stations first purchased helicopters, one of the advertisements promoting this new news resource was inadvertently filmed less than 100 feet from the nesting Fremont peregrines. A quick call from a vigilant volunteer led to a quick retreat by the helicopters and prevented almost certain nest failure.

Later in the nesting season volunteers provided dawn to dark protection for prematurely fledging, ground bound falcons. At Fremont the young typically spend between one and three days on the ground before they take flight. Much of the volunteer effort goes simply toward keeping curious peregrine watchers back away from the youngsters so that the parents will feel safe to land and feed them. However volunteers have also pulled young falcons from the river and out of the path of oncoming trains and cars. One youngster even had to be retrieved from a six-foot deep hole full of excrement that the local homeless community used as a latrine. Out of 25 youngsters that have been hatched on the Fremont Bridge between 1994 and 2002, 15 have survived the fledging process and twelve of those birds required some sort of intervention or rescue. The goal in every case was to provide the young falcons with the support and protection necessary to allow them to successfully achieve flight in the wilds of Portland, under the direct care of their parents.

An Expanding Urban Peregrine Population

Today peregrine falcons nest at five different locations within the city limits of Portland and our urban peregrines comprise 5% of the known nesting peregrine population in the State of Oregon. The adult male peregrines at two urban sites, Saint John's and Abernethy Bridges are birds that originally fledged off of the Fremont Bridge. In 2001 Portland nest sites fledges 15 youngsters in a single season!

However, the challenges continue. Although peregrines were delisted under the Federal Endangered Species Act in 1999, they remain listed as "endangered" under the State of Oregon Endangered Species Act. Peregrines across the Oregon landscape continue to face real challenges to their long-term recovery. DDT has an extremely long half-life and pesticides that were sprayed decades ago continue to linger in our environment to this day. Although their numbers have increased, Forest Service Peregrine Specialist Joel Pagel reports that every nest site he has entered in the Pacific Northwest continues to show levels of eggshell thinning higher than that prior to the use of DDT. On the local front we have at least one nest site that faces serious contamination issues. An addled egg from the Saint John's Bridge collected by Joel Pagel in 1996 contained very high levels of DDT, dieldrin and PCb's, the origin of which most likely is derived from a nearby superfund site.

The biggest challenge in the urban environment continues to be managing the potential for human disturbance. Ongoing educational outreach has created a community with a high level of both awareness and appreciation for the falcons. Local businesses, agencies and individuals have voluntary altered their practices to best accommodate their winged neighbors. They have provided additional eyes and ears to help sound the alarm when either deliberate or inadvertent disturbance occurs.

Today residents of the Portland metro area can look skyward and see the silhouette of a peregrine falcon slicing through the clouds. Visitors to the narrow strip of greenway the runs along the west bank of the Willamette River beneath the Fremont Bridge or to Cathedral Park beneath the east end of the Saint John's Bridge can observe peregrines going through their nesting cycle. Although peregrine means "wanderer" and peregrines are known for migrating huge distances, our urban peregrines tend to be year-round residents and are likely to be spotted near the bridges at any time of the year. It is a vision that we came close to losing forever, and one that we should never take for granted.

For more information on the peregrines of Portland or the Peregrine Watch Project, contact Bob Sallinger at the Audubon Society of Portland at bsallinger@audubonportland .org.

All photographs and text © Bob Sallinger 2003