How can I tell the difference between crows and ravens?

• Physical size. Common Ravens are about twice the size of American Crows. 
• Hackles. Ravens have heavily textured throat feathers called hackles, which are easier to see close up. They are used for visual communication by puffing up. Ravens can also raise the feathers above their eyes. 
• In flight:
  • Tail shape. Ravens have wedge-shaped tails, whereas crows have fan-shaped tails.
  • Proportion of flight feathers. From afar, ravens look like they have 4 prominent flight feathers whereas crows look like they have 5.
• Vocalization. American Crows make the classic “caw” that we are all very familiar with. For Fish Crows, the caw sounds more nasally. Common Ravens can make deep croaks, although they can also make lots of other sounds, too.

What are some best practices for feeding crows and ravens?

• Practice restraint. Dr. Swift’s general rule of thumb for feeding crows is to only target the pair or family that lives in your area. Don’t put out huge amounts of food to attract a large “murder” of crows.
  • Why? Unlike other common feeder birds, crows are generalist feeders, including predators. During the breeding season, if there are lots of crows around, this may be harmful to other nesting birds due to nest predation. 
  • People have concerns that crows are partially responsible for the recent decline trends in backyard bird populations, however, many predator exclusion studies show that this is not true. As mentioned before, crows can be harmful to breeding birds, but this is more on the neighborhood level and not the overall population level across North America. American Crows are also in decline, too. 
  • If you feed a pair of crows that is already established in your neighborhood, this is unlikely to become a problem. But remember, the goal is not to sustain the crows – crows can find food throughout the neighborhood and survive without you feeding them. A small handful of food a day is more than enough. 
• Be patient. Building trust with crows can take time, especially if the crows had negative experiences with humans. In the beginning, limit interactions to just giving food, not other gifts. Ravens especially are neophobic (that is, frightened of new things), so putting out a new offering might scare them off. Once they get more comfortable with you, they may interact with other types of offerings, which can be entertaining for us. The idea that ravens and crows like and collect shiny things is largely a myth and there is no evidence of them preferring shiny things over non-shiny things.  
• What should I feed crows? Unshelled nuts or soaked pet kibble are good options. For the latter, just add water to swell the kibble, store it in the fridge, then put it out on feeders.

How do crows respond to the dead?

Observable behavioral responses

• When a crow discovers a dead crow, the crow will produce an alarm call, which attracts other crows to the area. Those crows join in making calls, adding to the cacophony of noise. Eventually, they leave until just a couple of territorial crows are left. Then, eventually, these individuals leave, too. 
• During the breeding season, crows might exhibit some other behaviors in response to another dead crow. Crows have been observed interacting with the dead crows with tentative pecks, or moving the deceased crow’s feathers. Although very rare, crows have also been observed behaving aggressively or sexually towards the dead crow.
• TLDR; there’s a spectrum of how crows respond to the dead. 

So, do crows mourn?

• When researchers used PET imaging to analyze brain activity in crows in response to seeing a dead crow, they found that the area of the brain responsible for thinking was most active, rather than the area dedicated to emotional processing. Dr. Swift says that this doesn’t necessarily mean that crows do not “mourn.” Mourning is a complex phenomenon, and just because we cannot detect an emotional response similar to humans does not mean there is no emotional response at all. She brings forward the open question, is there a deeper emotional narrative that we can’t see? Given the highly intelligent and social nature of crows, Dr. Swift relays that she would not be surprised if the answer is yes. However, from a purely scientific stance, she cannot say for certain that crows “mourn,” especially in the emotional sense we typically think about mourning as humans, but she cannot say that they certainly do not, either.
• Note that existing studies on crow responses to the dead were done by presenting living crows with unfamiliar dead crows, rather than dead crows from the local population. From her experience, Dr. Swift did not notice a difference in the way crows responded to a crow in the neighborhood that died of natural causes.

How do other birds respond to the dead?

• Studies of other corvids have found that they respond to the dead similarly to crows.
• Some other birds have been found to have a clear recognition of the dead, others not, and their responses vary greatly depending on the species. For some birds, their response is avoidance, in which case they immediately leave the vicinity of the dead bird. However, other birds, such as pigeons, seem largely unbothered by the dead. 
• All in all, Dr. Swift stresses the importance of viewing these responses in the context of each species’ natural histories. One reaction is not necessarily better than another; one type of reaction could be advantageous for one species but disadvantageous for another. 

What do we know about corvid intelligence?

Do crows use tools?

• Many people, birders and nonbirders alike, are fascinated by crows and other corvids because of their intelligence, and especially their use of tools. This topic became popularized by the media, and unfortunately some of the specificity has been lost in the process, where crows (or members of the genus Corvus) have been lumped together despite being such a large and diverse genus of birds. Dr. Swift reminded us that there are forty-five species of crows that we know of in the world. However, most of the studies that are referenced in these popular articles on crow intelligence are about the the New Caledonian Crow, which has been made into the poster child of “tool-making crow.” In reality, not many other crows make tools, and this behavior isn’t as widespread as people think it is. 
• Dr. Swift also brings up an important distinction between using tools and making tools. She states that 1% of animals use tools, and of that 1%, less than 10% actually make them. The New Caledinian Crow is one of the 0.1%. 
• How did took-making and tool-use evolve in New Caledonian Crows? The very simplified answer is because there are no woodpeckers in New Caledonia, leaving an open food niche of insects under bark. Since the crows don’t have beak physiology to extract these insects, they turned to tool-making and tool-use to exploit the food niche.

How did crows evolve to be so smart? 

• There are many factors that influence evolution, and there isn’t really a clear answer. In the case of crows, these birds are generalists and highly social – features which likely promote problem solving and creativity. Like other urban exploiters, crows tend to be good at problem solving, which allows them to better adapt to anthropogenic change. Social dynamics and intelligence are often observed together, leading to a chicken-or-egg dilemma of whether these birds are smart because they’re social, or social because they’re smart. 

How common is play in corvids?

• Play behavior in birds is relatively uncommon. Examples of birds documented to play include ravens, hornbills, and parrots. One cool type of play observed in ravens is sliding in snow!

Can crows recognize human faces?

• Dr. Swift says that crows can absolutely learn people’s faces. They can learn through positive interactions (e.g., a person feeding crows) or a experience negative (e.g., a person harassing or killing crows). Dr. John Marzluff, professor and researcher at the University of Washington, found that crows can learn faces from just one negative experience. 
• At first, crows recognize people by learning their faces, but with time, crows can learn other features (e.g., body language). However, their facial recognition is not perfect; unfortunately, some people do get mistaken for another person with whom a crow has had a bad experience.
• Crows are able to communicate their knowledge of people (e.g., good or bad) to other crows, especially if they had a negative encounter with them. Crows react to a “bad” person when they encounter them again by dive bombing, which indicates to the naïve bird that this person is a threat. Naïve birds then learn the person, internalize that knowledge, and respond to the person when they encounter them, thereby passing along this knowledge to their peers and across generations.

Bonus Questions

During the watch party, we received hundreds of questions on corvids from curious FeederWatchers; below are answers to some of the most popular questions that we were not able to cover during the event!

Do crows mate for life? What is their social structure like? Are they a cooperative species? Why do some roost in huge groups?

• Yes, crows are socially monogamous, which means that mated pairs stay together for life. While divorce is rare, it can happen. Even among mated pairs, genetic evidence shows that extra-pair matings do occur, resulting in offspring not sired by the male partner.
• As a species, American Crows breed cooperatively, which means that non-breeding adult or subadult birds will stay on the territory and “help” the primary pair during the breeding season. Not all pairs have helpers, however, and rates of cooperative breeding seem to vary regionally. Helpers can consist of both related offspring and unrelated birds. The type of help varies between different populations, but these behaviors include bringing sticks to the nest, feeding incubating females, cleaning the nest, and guarding eggs and nestlings.
• Roosting depends on various factors, from time of year, to age of the bird, to breeding status. Roost size typically begins increasing in late summer, grows through the fall as migrants join in, and peak in winter. These roosts can grow to incredibly high numbers, with hundreds of thousands of individuals at a signal communal roost. Roosting in large groups mainly helps protect crows from predators, but other purposes could include staying warm and socializing.

How do crows communicate? What do their different calls mean?

• Crows communicate in several ways, from vocally to using body language. They have many different types of calls that they use to communicate with each other. “Caw” is the most common call, and is used year-round and helps crows to communicate over long distances. There are several variations of the caw, including Short Caw (alarm call), Medium Caw (territorial, contact, assembly, dispersal, etc.), and Harsh Caw (mobbing). Given what we know about the vocal communication of many other birds, it may surprise people to learn that there is still much left to discover about crow calls. This is in part because crows do not exhibit referential calling, which is when specific calls are associated with specific objects or events in the environment. Among birds, chickadees are a well-known example of referential callers, where the number of trailing “dees” relates to the intensity of the threat. Crow communication appears to be much more context dependent, and there are many common crow calls for which scientists still have not identified a clear and consistent meaning. A familiar example may the “wow” type calls which sounds like a low, hollow “wow” “whomp” or murmur. Crows produce these sounds in many different contexts and their exact meaning remains unknown.

How are crows doing today? Are there any declines in their populations?

• Overall, crows have been in decline for the past couple of decades due to the West Nile Virus that decimated crow populations starting in 1999. The most recent data released from the North American Breeding Bird Survey are from 2022, so we do not know whether their populations have stabilized or have continued to decline since then. eBird trends from 2012–2022 also show widespread declines in American Crow populations.

Can you discuss the relationship between some corvid species (such as ravens) and predatory mammals such as wolves or coyotes?

• Ravens are known to follow animals such as wolves and coyotes to scavenge on prey killed by these predatory mammals. However, it is clear that these interactions are not of a special “friendship” as commonly reported, and ravens remain very cautious when feeding near canids, as canids can respond violently to having their food stolen. There has not been scientific evidence that supports the idea that ravens are leading wolves or coyotes to large prey.

Feel free to share your own story with crows in the comments below!