As children growing up in Riverside, my friends and I were captivated by crows, big birds that were bold. We used to see how close we could creep toward them, while they seemed to contemplate our attention before flying away. What were they cawing about us?

Not long ago, the following email message arrived in the Reader offices. “Originally, the only crows I had ever seen,” observed the writer, “were at Death Valley. Now, they are all over La Jolla, walking on my wooden roof with scratchy nails, standing in the treetops, doubtless robbing babies from nests of other birds, leaving huge poops down the side of my house and on the front sidewalk. How come they have moved in such numbers to the coast? We used to have mostly raucous mockingbirds, but now it’s crows. There must be a reason for this migration.”

There must be a reason all right, but local bird experts aren’t sure what it is.

One of them is Terry Hunefeld, who has just returned from leading a seabird-watching expedition past San Clemente Island, 110 miles into the Pacific. “There are birds far out on the ocean, such as albatrosses,” he says, “that people never even see from land. They sometimes fly for thousands of miles before coming down.”

In contrast, crows tend to be stay-at-home birds. But if the La Jolla emailer is correct, they must have once left their inland habitats, right? Yes, Hunefeld tells me, in the early to mid-1980s, many of them suddenly seemed to pick up stakes and move into urban and coastal San Diego. Why they did it then, but not earlier, nobody adequately explains.

Crows seemed rarely to venture farther west than places like Poway, Lakeside, and El Cajon. “Those areas, and especially oak and riparian woodlands, were their native habitat,” says Hunefeld, who is 56 and retired from the real estate–training business. (He has always liked to spend time outdoors and, about eight years ago, got a serious case of bird-watching fervor.) “And even though San Diego was becoming a metropolis for a long time, it’s a mystery to ornithologists why the crows waited to move into the city, why they didn’t do it in the 1960s or 1970s, for instance. And why did it happen so quickly in the 1980s and 1990s?”

Hunefeld is most familiar with crow populations of the coastal valleys of Oceanside. He has been the compiler for the Audubon Society’s Christmas bird counts there for the past several years. “In Oceanside, 20-plus years ago,” Hunefeld tells me, “the count would average several hundred crows. In the late 1990s, it was up to 1000, 1400 in 2006, and when we counted last December, it was 1900.”

For further information on crows, Hunefeld refers me to Philip Unitt’s San Diego County Bird Atlas. Unitt is the curator of the Department of Birds and Mammals at the San Diego Natural History Museum. According to the atlas, American crows (Corvus brachyrhynchos) “nest in the crowns of trees with dense foliage.” Originally, coast live oaks in foothill areas were their favorites, but now that crows have moved to town, they inhabit “palms, pines, Italian cypress, and especially eucalyptus. In groves of such trees, crows nest colonially.”

In winter, crows gather in large flocks and roosts. Despite their more recent urban lifestyle, the highest concentration of crow populations in San Diego County, according to the bird atlas, is still “at the east end of Lake Hodges.”

Susceptibility to West Nile virus has become a particular hazard to crows. The virus “appeared in New York City in 1999,” says the atlas, “and is spreading rapidly across North America; crows have already been decimated in parts of the eastern United States.”

Other corvids are rooks, jays, and common ravens (Corvus corax). It is easy to confuse ravens and crows. But ravens are much bigger birds than crows, says Terry Hunefeld, in length, weight, and wingspan. Ravens have a shorter beak that’s somewhat like a “Roman nose,” and their wings are pointed, unlike those of crows. Ravens have longer tails than the fan-shaped crow tail. When the cousins fight, the single great advantage crows have over ravens is greater maneuverability in the air.

Ravens have long been local residents. “After the house finch,” according to Unitt’s bird atlas, “the Common Raven is the most widespread breeding bird in San Diego County. It occurs in all habitats, from beaches to mountaintops to desert floor. The change in the raven is less dramatic than that of the…crow, but the raven too is on the increase, aided by man-made…food sources…road kill, and…nest sites like buildings, bridges, and power-line towers.” They nest, for instance, in the California Tower in Balboa Park.

Crows are more communal than ravens. It’s hard to tell the male crows from the females. Both, together with extended families, take care of their young in nests at common roosts, which may be home to hundreds of crows. Egg laying in the San Diego region occurs roughly from the second week in March to mid-May. The incubation period is 18 days, according to the bird atlas.

Many people think of crows as a great nuisance. “They definitely can be annoying,” says Hunefeld, “especially in the evening, when they are calling to let each other know where they are.”

No matter what other people think, Hunefeld seems to be as fascinated with crows as with other birds. He concedes that he goes out bird-watching every day for one unique chance — to spot exotic birds. “Birds from the East Coast sometimes fly in here,” he says. “They just make a wrong turn during their migrations. And every once in a while, we’ll see Asian birds that, like the birds on our Pacific Flyway, go to Alaska for the summer. Then they just go back down the wrong coast.”

But crows? “Due to their cooperative and social nature, they may be the smartest bird out there,” says Hunefeld. “Crows will call warnings to each other and, in small groups, will chase away competitors.” They fight them off for food but will stand watch while their own family members eat.

“Crows are scavengers and will eat just about anything,” says Hunefeld. “So they are predators on the eggs and young of other birds.” They inhabit residential neighborhoods because they get lots to eat from picnics in parks, french fries and pieces of doughnuts on the sidewalk, and half-eaten burritos thrown from car windows. They help clean up refuse.

In that respect, crows’ urban existence is similar to their lives in earlier times. Farmers used to hate crows for eating their grain and fruit. But the crows fed on destructive insects at the same time.

On a neighborhood walk, you can often come surprisingly close to crows pecking at something on the ground. If you move in a way they find threatening, of course, they’re gone. “But they also recognize friendly gestures,” says Hunefeld. “When I was a kid, we helped a crow in our classroom to recover from a broken wing. For the next two years, he kept coming back for handouts.”

A number of websites attest to great affection for crows. I attach the following reminiscence entitled “Ball Playing Crows” from crows.net, The Language and Culture of Crows.

Washington State, near Seattle. “Grocery store, strip mall roof. As I approached the covered breezeway I could see several crows, maybe 5 or 6, ‘jumping’ up and down on the roof.… A moment later a super-ball dropped off the roof and bounced into the busy parking lot; three crows quickly followed and chased the ball while it bounced. When the ball came to rest in a gutter one of the crows picked the ball up in her beak and ‘threw’ it. At that point the other crows all tried to catch it. Even when it rolled under cars they would pursue the ball and make it bounce.…

“After about 10 minutes the ‘owner’ of the ball took the ball back up to the roof where I could once again hear the bouncing and jumping. The super-ball was one of the 2” diameter ones; so it was really an effort for them to pick it up and then fly.”

And now I notice on crows.net a possible answer to why crows suddenly moved from the backcountry into the San Diego urban area. “I was driving by when I noticed hundreds of crows gathering.… They were landing on top of the fence and all the way down covering all the ‘terraces.’ They stood in place all the way to the sidewalk. After a few minutes the area was packed with crows. Two crows were standing in the bicycle path by the street next to the sidewalk. One of them made a sound and all the other crows became silent facing the ones in the bottom. Then the second began making sounds. After about three minutes, the second crow stopped making sounds and the first one made a sound and all the others began flying off.

“The first thing that came to my mind when I saw this was that they were in an amphitheater listening to a lecture. I was amazed that they all stayed quiet while the one in the bottom was ‘speaking’ and none flew away during all this time. I was also surprised at how instantly they grew quiet when the first crow made the first sounds and how quickly they left when ‘he’ made the second sound.”