American Crow adult
Famous for their cleverness, crows compare favorably to humans in many ways, especially their family lives. Mated pairs remain together with more durable bonds, separating and divorcing far less frequently than human couples. Both crow parents, with help from their offspring from previous years, raise new broods of young each year with steady patience. Crows are self-sufficient yet essential members of their community.
American Crow adult
American Crows live in extended families, defending a year-round territory in which they nest and forage. They communicate through a wide variety of calls and body postures.
Within the sightline of people throughout North America every day of the year, crows still manage to keep their private lives private. Researchers at the Cornell Lab and elsewhere have teased out important facts about their breeding habits.
As the breeding season nears, members of a pair often sit close together, engaging in allopreening and billing, in which they gently touch and grasp each other’s bills.
Crows mate for life and stay bonded to their mate throughout the year. This may be why they have few courtship displays. In their bowing display, one crow jerks its head up and down a few times, then bows, clacking its bill. Crows perform this display during courtship and other situations as well.
Surging hormones and increasing day length prompt crows to nest. Many people consider crows carrying sticks as the first sign of spring. Both male and female bring nesting materials, helped by offspring from previous years. The breeding pair constructs the bulky nest of twigs, the mother shaping the inner cup and lining it with fine fibers such as pine needles, dead weeds and grasses, soft bark shreds, and animal hair. Crow nests are often used in subsequent years by Merlins (small falcons) and medium-sized owls.
The mother crow starts to incubate after her clutch of three to nine eggs is complete. She incubates all night and 86 to 90 percent of daytime as her offspring from previous years forage and feed her. When off duty, she stretches her legs and wings, defecates, preens, and hurries back to the nest, usually without eating anything. While she’s incubating, her mate stays within sight, perched somewhere conspicuous to guard her. If the pair doesn’t have helpers, he spends some time away finding food.
The father and helpers spend more time at the nest when the first eggs start hatching, after 16 to 19 days, but now they’re less focused on feeding the female and more curious about the hatching process. The eggshells disappear within a few hours or a day of hatching; the birds may eat the shells, carry them off, or just toss them out of the nest.
Brooding the chicks almost continuously for 9 to 14 days after the first egg hatches, the mother leaves only to poop, preen, and stretch a bit. Her mate and their helpers feed her and the chicks. As the nestlings grow and start maintaining their own body temperature, they start needing more food; now their mother starts foraging and feeding them, too.
A crow pulls up dead plant material to line its nest in a suburban backyard. Both members of the pair build the nest, sometimes helped by their adult offspring from previous years.
A close-up of a crow’s nest containing five eggs. Notice the different materials used in each layer of the nest: large twigs outside, dry grasses next, and reddish-brown bark shreds lining the cup. The nest can be up to 19 inches across.
A crow’s nest with eggs sits high in a white pine. Crows usually hide their nests in the upper third of a tree, often in a crotch near the trunk or on a horizontal branch. They prefer conifers, but will settle for deciduous trees, and often nest near last year’s nest, sometimes in the same tree.
Crows have more than 20 distinct calls, including many variants of the familiar caw, differing in quality, duration, and function. A cawing display, in which the calling crow partly spreads its wings, fans its tail, and swings its head down and up, may be employed during territorial defense. The assembly call is an intense and raucous series of long drawn-out caws, summoning nearby crows to help drive off a predator (frequently a Great Horned Owl).
Three adult crows attend a nest. Thanks to wing tags put on birds by researchers at the Cornell Lab of Ornithology and other New York institutions, these crows can be identified and their relationships to one another and to the nestlings can be worked out. This is how we know that crows often breed cooperatively: sons or daughters from previous years help raise their own younger siblings. The entire family participates in feeding the young.
Newly hatched. Two adult American Crows feed anestling. The young are altricial, hatching blind and helpless, with sparse, grayish down. These two adults may be the hatchling’s parents or one or more of its older siblings.
8 days old. Four crow nestlings huddle in their nest. Sparse gray down covers crowns and backs; eyes are still closed, not fully open until 10 to 13 days of age. Dark feather tracts are developing under the skin; pinfeathers will break through at 10 to 11 days.
14 days old, Growth spurt. Eyes still not quite open and wing feathers at the brush stage (partially broken free of their sheaths), these nestlings still have downy crowns. Their bodies grow the fastest between 8 and 18 days, their wings outgrowing their already strong legs.
25 days old. These nestlings are fully feathered but still show a few wisps of down. Soon they will begin flapping their wings; some may start venturing out of the nest, along branches and back again, days before fledging. The parents may place food on nearby branches to encourage them.
Crow chicks remain in the nest for at least a month. When they first fledge, their tails are still short and they can only hop from branch to branch. It takes several days to develop flight skills. Fledglings depend almost entirely on their parents for feedings for weeks after leaving the nest. Once they can fly well enough, their parents lead them to areas to find their own food.
Gradually growing independent, they remain in close contact with their family and neighbors for life. Many of them help their parents raise a few broods of siblings before starting their own families.
West Nile virus, which hit upstate New York in 2002 and 2003, is far more lethal to crows than to most animals, including humans. Crows die too quickly to transmit the disease, but their sudden deaths serve as our first warnings of danger.
When dead crows with individual tags began to appear in Ithaca, New York, scientists at the Cornell Lab were able to track and study family ties. After one adult male lost his mate and young to the disease, he spent the remainder of the nesting season helping his neighbors raise their young.
A different adult male died along with the nesting pair in an adjacent territory; his surviving mate took over caring for the neighbors’ young. The following year, those adopted crows helped her raise her next brood.
Like humans, crows put themselves and their families first, but they seem to care about their wider community as well.