American Crows (Corvus brachyrhynchos) are one of our most common and fascinating urban wildlife residents. Crows are highly intelligent birds that can survive and proliferate in a wide array of different habitat types including our urban environments. Their highly visible nesting activities throughout our neighborhoods during the spring and summer and a massive population of crows that roost downtown during the fall and winter arouse wonder, appreciation and occasionally conflicts. Portland has developed some cutting edge strategies to protect and manage our urban crow populations.
During spring and summer, crows will break into small family groups and nest in trees and on ledges across our urban landscape. Young from the prior year will often help their parents raise the following year’s offspring, so it is not uncommon to see five or six crows working together to support a nest or protect a fledgling. During the fall and winter, crows will spend their days foraging across the landscape, but will come together in the evening to form large communal roosts. Scientists believe that these communal roosts provide crows with safety from predators, warmth and allow for information exchange. These roosts can range in size from a few dozen birds to tens of thousands.
Crows are protected under the Migratory Bird Act of 1918. It is illegal to physically harm a crow or to destroy an active nest unless very specific federal regulations are followed. It is also illegal to keep a crow as a pet. Only facilities that possess federal permits to hold crows for educational purposes or research are allowed to keep crows in captivity.
Crows are often taken for granted, but can be fascinating to watch. If you have crows nesting in your neighborhood, watch how the extended family unit works together to raise the young. If you have a winter crow roost in your neighborhood, enjoy what is truly an amazing wildlife exhibition as the crows fly in from all directions in the early evening, congregate in what has been described as a “raucous happy hour” and then move to their roost trees as night falls.
American Crow populations in North America are doing quite well. Unlike many species, they are more abundant today than when European settlers first arrived. Their ability to adapt to cleared agriculture landscapes and urban environments has allowed them to proliferate both in terms of population and range. Partners in Flight places their estimated global population size at 28 million birds and gives the American Crow its lowest threat rankings for breeding and non-breeding population distribution as well as threats to breeding and non-breeding populations. Christmas Bird Counts (CBCs) indicate that crow populations have been increasing significantly at a rate of 1.25% nationally. 1.07% in Oregon and 2.9% in Portland over the past several decades.
A 2019 report on North American bird declines aggregated a variety of different surveys and found that American Crow populations have declined slightly in recent decades. However, it is safe to say that American Crow populations remain near historically high levels.
- Crows are omnivorous and will eat just about anything, including fruits, vegetables, insects, small rodents, and even other birds and bird eggs. Given the opportunity, they will also raid garbage cans.
- Crows typically build a stick nest in a tall tree, but may also use ledges on man-made structures.
- Nest building occurs in late April and May. Crows lay 1-6 eggs, which are incubated for 18 days. The young remain in the nest for 28-35 days. It is common for youngsters to leave the nest before they are able to fly and they can spend up to several days on the ground.
- While young are learning to fly from the ground, both parents as well as offspring from the prior year care for youngsters. Young crows remain with the parents throughout the first year of life and help raise the following season’s offspring.
- Crow families will establish territories during the breeding season, but during the non-breeding season they gather at large communal roosts, or sleeping areas.
- Communal roosts can range from a few dozen birds to tens of thousands of birds. Some roosts have grown to include several hundred thousand birds! During the day, crows disperse to forage and return to the roost in the evening. Crows remain in the Portland Metro Region year round. They are considered resident birds.
- Crows are in the corvid family which also includes ravens, jays, magpies and nutcrackers.
Common Situations or Concerns
Fledgling Crows on the Ground
Like many species, juvenile crows will typically leave the nest before they are able to fly. They can spend up to several days on the ground building up their flight capabilities and learning essential survival skills from their families. This is a completely normal and very important part of their life cycle. It is not uncommon to find young crows on the ground in suburban, urban and industrial areas during the months of May, June, and July.
Fledgling crows are as large as adults, and people are frequently concerned that the crow they have seen on the ground is an injured adult rather than simply a youngster learning to fly. One easy way to tell if a crow is a juvenile is to look at the color of the bird’s eyes. Young crows have blue-grey eyes, while adults have black eyes.
Unless these birds are clearly injured, they should be left alone for their parents to care for. Crows that are in immediate danger can be placed up off the ground on a low branch or structure, but should not be moved more than 100 feet from where they were found.
Although the urban landscape may seem like a hazardous place for a crow to grow up, remaining under parental care is still the best thing for the youngster – crows spend between one and two years with their parents, learning complex life skills that are required to integrate into the species’ complex social structure. Captive-raised crows don’t have the benefit of parental guidance, and face many more challenges than their wild-raised counterparts. The parents and siblings from the prior year will return frequently to look after them while there are fledging.
Crows Are Making a Ruckus Near the Fledgling
Crows are very protective of their young and will bring food to the youngster, attempt to direct it away from harm and drive off potential predators. The family may not always be present but they are usually close by.
Sometimes protective behavior by adult crows can be confused for aggression against the youngster, but rest assured that the presence of loud, raucous group of adult crows is a sign that a youngster is in good hands.
Aggression Towards Pets and Humans
Both pets and humans are far beyond the size of crow prey. Aggression is almost always the result of adult crows protecting nearby nest or young on the ground and is limited to a very small area. It is a temporary situation that is best resolved by trying to avoid the area they are protecting. While it can be intimidating, crows do not present a significant threat to humans, dogs or cats.
Unwanted Crow Roosts in the Neighborhood
Crows form large communal roosts in the evening to help them survive the harsher winter months. These roosts are fascinating to observe and we generally encourage people to be tolerant of the noise and fecal matter that can be associated with these roosts. When significant conflicts do occur, we promote non-lethal, humane strategies to encourage the crows to move elsewhere. Use of poisons or other lethal control strategies is never appropriate and can result in violation of federal laws, unnecessary crow mortality and can put people pets and non-target wildlife at risk as well. Crows can sometimes be deterred from roosting in high conflict areas through the use of a variety of non-lethal techniques. The best solution or combination of solutions will depend on the circumstances and some strategies should only be employed by trained professionals. Many of these strategies will only result in short-distance displacement and crows may attempt to return to roost sites if strategies are discontinued.
Strategies include the following:
- Tolerance: Remember that crows form communal roosts to help them survive the harsher winter months. There are fascinating to watch and will disperse as spring begins to arrive.
- Reduction of human food subsidies: Eliminate accessible human food sources such as garbage, downed fruit, compost, etc. which may support the roost and allow it to grow over time.
- Reduction in outdoor lighting: While the science is still inconclusive, there is some evidence that crows may be attracted to better lit areas. Reducing outdoor lighting and ensuring that all outdoor lighting is aimed downward and covers only the target area may help reduce wildlife conflicts as well as light pollution.
- Active hazing: For smaller roosts that are just forming, simple noisemaking, such as banging pots and pans together as the birds congregate may be effective. Also scare devices such as scarecrows, owl effigies, and reflective Mylar tape can be effective. Scare devices are most effective if moved frequently so crows don’t get used to them. For larger more established roosts, strategies such as use of sound cannons, lasers, pre-recorded distress call, and use of falconry birds can be effective but typically will require professional assistance.
All of these strategies have their limitations and even with hazing, crows will typically remain in the local area, but limited displacement may be adequate to relieve significant conflict situations.
Crows Raiding the Nests of Other Birds
Crows will prey upon small birds and will consume other birds’ eggs. While this may be difficult to watch, predation is natural and we urge people not to attempt to intervene. Similarly, crows may themselves be preyed upon by larger predators such as Red-tailed Hawks and Great Horned Owls.
Poisons are Never Appropriate for Resolving Conflicts
The use of poisons is never an appropriate strategy for resolving crow conflict situations. Poisons are indiscriminate and inhumane and place not only the crows at risk, but also people, pets and non-target wildlife. Portland has had several poisoning events in recent years, In 2014 and 2018 illegal use of the restricted-use avicide (bird poison) Avitrol ™, a neurotoxin, resulted in mortality events where large numbers of crows literally fell out of the sky over dozens of city blocks in downtown (2014) and Northeast Portland (2018) and lay seizing, screaming and dying on the ground. Audubon, the City and other agencies had to mobilize significant resources to collect dead poisoned crows from yards, sidewalks, roads, and parks where they presented a risk of secondary poisoning to people, pets and non-target wildlife.
Similar events have occurred in other cities across the United States. On June 5, 2019, The City of Portland passed a resolution to ban Avitrol™ and other bird poisons from use on city owned and managed lands in Portland. Portland Audubon is now working to get the Environmental Protection Agency to revoke Avitrol’s™ registration for use.
- KATU Coverage of 2018 Crow Poisoning Event in NE Portland
- View June 5, 2019 Portland City Council Hearing Banning Avitrol™ and other bird poisons
- OPB Story: June 5, 2019 Portland Bans Toxic Bird Poisons on city Property
- Read the Resolution Banning Avitrol
Other Portland Audubon Corvid Related Projects
Portland Audubon is currently opposing a proposal by the Oregon Department of Fish and Wildlife and US Fish to poison ravens in Baker County, Oregon. ODFW is blaming ravens for declining local populations of Greater Sage-grouse. While Portland Audubon strongly supports efforts to recover sage-grouse, we are concerned that the agency has produced no data linking raven predation to local sage-grouse declines while ignoring other confirmed threats to sage-grouse. We are also concerned that the poisoning proposal is inhumane and presents a high level of risk to kill far more ravens than anticipated as well as non-target bird and wildlife species.
- See March 7, 2019 Portland Audubon Action Alert regarding proposed lethal control of ravens in Baker County.
- Read March 2019 OPB Story: Bird Advocates Question Raven-killing Plans to Protect Sage-grouse
- Read Portland Audubon April 2019 Blog by Bob Sallinger: Another Senseless Slaughter: Raven killing in Baker County.
- Read Comments from Portland Audubon et al. regarding proposed lethal control of ravens in Baker County
- Read Portland Audubon’s statement regarding the decision by State and Federal Agencies not to kill ravens in Baker County during 2020