The Downtown Portland Crow Roost

Why Do Crows Form Winter Roosts?

Scientists believe that crows form winter roosts because there is safety in numbers, large number of birds provides  warmth during the harsher winter months and it allows for exchange of information among the crows. Roosts occur on both urban and rural landscapes. A variety of factors may attract crows to urban landscapes for roosting including warmer ambient temperatures, food subsidies provided by garbage cans and other accessible food sources, lighting, and reduced pressure from predators such as Great Horned Owls.

In spring and summer, crows  disperse out across the landscape in smaller territorial family groups to nest and raise young. However in the fall and winter,  crows There are a number of winter crow roosts scattered across Portland, but by far the largest is located in downtown Portland. Observers are treated to a remarkable wildlife event as crows converge on downtown Portland from all directions in the late afternoon. The birds will typically congregate in a variety of locations in raucous groups in what has been described as a “crow happy hour.”  In certain areas, virtually every tree and ledge can be covered in crows. As darkness falls, they settle into downtown trees to roost for the night. They will typically depart the roost in small groups before sunrise to forage across the landscape throughout the day.

Downtown Clean and Safe which is responsible for keeping the downtown core area clean has worked for many years to address challenges associated with accumulation of crow feces in high human traffic areas in an ecologically responsible and humane manner. Initially, Downtown Clean and Safe focused on sidewalk cleaning strategies including pressure washing and purchase of the “Poopmaster 6000,” a Zamboni-like device to clean streets and sidewalks. In 2016, they shifted to contracting licensed falconers to haze the crows out of a seven by ten block area as they congregate in the evening. We appreciate Downtown Clean and Safe for explicitly stating their commitment to finding humane, non-lethal, ecologically responsible solutions to address the conflicts that are occurring. Notably, Downtown Clean and Safe testified in support of a City of Portland ban on the use of bird poisons that have been used to kill crows in various locations in Portland and elsewhere.

While tolerance and coexistence with wildlife is our preferred strategy, we also recognize in some cases, conflicts do need to be addressed. Part of the reason Portland has become a national leader in urban wildlife conservation is its combination of aggressive programs to protect and promote wildlife and wild habitat and its innovative strategies to proactively resolve wildlife conflicts. 

Bird Alliance of Oregon has endorsed Downtown Clean and Safe’s approach to resolving its concerns. American Crow populations in Portland and at a continental scale are quite healthy. There are more American Crows today and they are more widespread that at the time of European settlement.  The Harris Hawks used for hazing have no direct contact with the crows. The hawks simply do short flights in the vicinity of the crows to shift them towards more acceptable locations. The hazing is likely to only move the crows a short distance and many crows are likely to remain within the hazing area. They are also likely to return if the hazing is discontinued. The objective is simply to cause enough displacement to alleviate the most intense concentrations of crow feces in downtown areas with the highest levels of human activity. There will still be thousands of crows roosting in downtown Portland and there will still ample opportunity for people to enjoy watching the crows. These type of non-lethal approaches to conflict resolution involving crows are recommended not only by Bird Alliance of Oregon but also Humane Society of the United States and the US Fish and Wildlife Service. 

Has the Hazing been Successful?

The hazing has been very successful. Five seasons of hazing activity have demonstrated that with regular hazing, the crows can be trained to avoid the downtown core area for roosting. The crows have relocated their roost to the trees in Waterfront Park where conflicts are much less significant. Once frequent complaints for downtown businesses and visitors have dropped to virtually zero and Downtown Clean and Safe has actively supported efforts to protect crows in Portland. And the crows have not only remained in the area but their numbers have continued to increase. The bottom line is that there are more crows than ever in downtown Portland, but that by shifting the location of the roost just a few blocks, using non-lethal, humane strategies, major conflicts have been alleviated. 

Why Can’t the Crows Remain in the Downtown Transit Mall Blocks?

In most cases, tolerance is the preferred strategy. However, the fecal matter produced by more than 10,000 crows night after night is prodigious. The feces coated sidewalks, awnings, benches, bus stops, outdoor furniture and signs. Extreme cleaning measures including daily pressure washing and purchase of a special sidewalk cleaning vehicle proved insufficient to alleviate the conflicts. Crow poop is corrosive and can present human health risks at high concentrations. Cleaning is particularly difficult in the transit mall area due to the complexity of the landscape, the porous brick pavers lack of organic substrate, and high human traffic volume. A shift of just a few blocks to park area has alleviated the most significant concerns while also allowing the downtown crow roost to increase in size.

Does More Research Need to Be Done Prior to Hazing?  

American Crows are a fascinating and complex species and there is a variety of research on this species that is ongoing. There is still much to learn about this species and its nesting, breeding, roosting, migration and social behaviors. However, that does not preclude management of significant conflict situations where they exist. Over the past five years, the downtown crow roost has shifted just a few blocks to more natural habitat and the overall number of roosting crows has increased. There are also a wide array of other potential alternative roost sites located across our urban landscape.  Downtown Clean and Safe has consistently sought out the least aggressive strategies to resolve conflicts. More data would not alter the basis for management activities in this situation.

Will the Hazing Harm Individual Crows or Crow Populations? 

Under natural situations, crow roosts are exposed to predation by raptors. It is simply part of their existence.  Crows could be predated by a variety of diurnal raptors such as Red-tailed Hawks, Coopers Hawks and Peregrines as they arrive in the later afternoon and early evening. They could be predated by nocturnal predators such as Great Horned Owls, Barred Owls as well as tree climbing mammals such as raccoons once they have settled-in for the night. Crows also are significant predators, especially on the nests of other birds. While the hazing using Harris Hawks is different from natural predation, it does in some ways mimic what crows would experience on more wild landscapes. Among the various hazing alternatives, it is probably least disruptive and closest to what they might experience under natural circumstances. Disruption does consume energy and may to some degree decrease the fitness of individual birds. However, it is important to note that the crows are just shifting a few blocks and that once hazing is initiated the vast majority of crows simply go to the waterfront, rather than entering the hazing area.  Overall, American Crow populations are doing very well. There are more American Crows in Portland, in Oregon and across North America today than there were at the time of European settlement. The Partners in Flight Avian Conservation Species Assessment Database estimates that there are 28 million American Crows in North America and gives American Crows their lowest threat rating for breeding and non-breeding distribution and for threats to breeding and non-breeding populations. It predicts that American Crow populations will remain stable or see small increases in the future. 

An Example of Living with Urban Wildlife

Portlander’s are fortunate to share our urban landscape with a wide range of fish and wildlife species. Our location at the confluence of two major rivers means that we will continue to play an important role in the lifecycle of many species. Portland has been a leader in many area of urban wildlife protection including creating a nationally recognize system of protected natural areas and greening the built landscape with trees, green roofs, green streets and certified habitat yards. It also includes innovative management strategies including management of Peregrine Falcons on Portland area bridges, management of Vaux Swifts in Chimneys, management of bird strike risks at Portland International Airport and information resources to help residents resolve human-wildlife conflicts in their homes and neighborhoods. Part of the way we protect our urban wildlife populations is by proactively preventing and managing conflicts. The management of the downtown crow roost stands as a case in point—Bird Alliance of Oregon, the City, Downtown Clean and Safe and other stakeholders have worked together to come up with innovative solutions that alleviate real conflicts while allowing the downtown crow roost to not only persist but grow in size just a few blocks away using the least aggressive management strategies available. 

For more information, Please contact Bird Alliance of Oregon Conservation Director, Bob Sallinger at bsallinger@birdallianceoregon.org