I’ve heard many claims about strange and fantastic behaviors of wild birds, especially those in the crow family. As a scientist, I am naturally skeptical, but as the following excerpt from my new book with Tony Angell, Gifts of the Crow, suggests, the scientific method can be used to better understand the amazing abilities of wild animals. Have a read through it and let me know if you have had similar experiences with birds or anecdotal claims.

The possibility that crows knowingly manipulate people was raised by Gary Clark and many others who daily feed wild corvids. Gary carefully trims the skin and fat from fresh chicken. A pound or more of the greasy mess bloats a plastic bag next to him. He grabs the swollen container, a few slices of old pizza, and a tub of dog kibble and peanuts and heads out to feed the crows. His collection of scraps and goodies today is usual crow fare. We’ve done our own share of direct recycling from kitchen to crow.

Today Gary is rewarded nearly immediately after he steps into his backyard, rattles the dry dog food-and-peanut dinner “bell,” and plops the pizza and chicken onto the elevated TV dinner tray rooted by four legs into his lawn. Shortly after we hear a single crow call in the distance, a crow alights in the cherry tree above the feeder. Then two more arrive, and within a few minutes, 15 to 25 hungry crows drop from a wet sky into a typical suburban backyard to devour the carefully blended feast. We are transfixed by the black shapes beyond the glass doors as they fly acrobatically, call, chase, and wrestle with one another, even jostling for tidbits with several resident squirrels. To Gary’s amusement, the ever-changing scene is fascinating, engrossing, and yet mostly predictable. These wild animals take him from the confinement of a well insulated, fully bric-a-brac’d house into a wild, dynamic scene. They also provide the additional benefit of lawn care as some of the crows pluck cranefly larvae from his well-tailored grass.

Today’s activity was pretty routine, but barely two years before, at this same spot, something very unusual happened. Gary had been heaping his tray with crow chow for a couple of years, when just after Valentine’s Day, 2006, he talked to a small hungry flock gathered above him in the cherry tree. A big man with a military bearing and haircut, he nevertheless evoked an open-armed solicitation and asked the assembled birds: “Hey, how come you never bring me anything? I always give you food, and you never bring me anything.” With that he returned to the house and the crows quickly descended to eat everything he had left on the tray. Late in the afternoon, long after the feeder had been picked clean, a small purple object on the feeding tray caught Gary’s eye. “What the hell is that?” he asked himself. Upon inspection, he was stunned to see a candy heart centered on its surface. It was well worn, but clearly visible on one side was the word “love.”

“Right. You’ve got to be joking. A touching gift from beast to man” were our first thoughts when Gary emailed us his story. We came up with seven hypotheses that are consistent with the episode.

Crows understand the spoken and written word. Some person had pulled Gary’s chain. Gary had pulled our chains. Some other non-human animal had carried the heart to the tray and dropped it by accident. Gary had encountered a former pet or trained crow. Gifting was real, but a mistake. Gifting was real and purposeful, maybe a form of reciprocity or coercion by the crow.

How do these seven plausible, scientific hypotheses stand up to the data? Consider the hypothesis of chain-pulling. We figured either Gary was crazy or the butt of an interesting prank. Gary lives only a few miles from us, so we paid him a visit. Gary’s yard is fenced. He and his wife, Sue, have no children at home. Sue suffers from rheumatoid arthritis, and on crutches, wouldn’t likely sneak out to the back yard merely for a prank. His neighbors do not appreciate the crows’ daily ruckus, and if they could have accessed the feeder, certainly they would have left a different message. This heart, as unbelievable as it seems, was unlikely to have been left on the feeder by a person. It could have been left on the feeder by a crow or possibly a squirrel.

Two years later, Gary is still awed by the gift. And now he also has a small metal butterfly, a round cylinder of cement, a fir cone, twig, and dried berry to add to the collection. All are carefully kept in a special jar. Each item was left on his feeder after crows devoured what he provided. Gary and Sue are convinced the crows, or at least one stalwart sentinel crow who routinely patrolled the yard, understood Gary’s plea and him the candy heart. Of late, the gifting is on hold. Perhaps the generous, familiar crow no longer lives in the neighborhood.

Gary is not the first or only person to receive a gift from a crow. Nancy, from Bristol, Indiana, called in to the Diane Rehm radio talk show to tell us about a crow that had visited her and given her a small wooden bead. She had been sitting on pillows, reading a book in her yard, when suddenly a crow dropped from the sky, landed on her lap, and left an inch-long necklace bead on her leg. Nancy was shocked. She did not feed crows and in fact rarely noticed them in her neighborhood. She kept the bead. Nancy did not talk to her crows and there was no writing on the bead, so we can safely reject Hypothesis 1. Crows need not understand the spoken or written word to leave gifts.

The bold behavior of Nancy’s bird suggested a former pet animal, habituated or imprinted on humans. Raising a crow as a pet is a common, albeit today, illegal activity. Owners of pet crows report receiving bottle caps, pull tabs, coins, false teeth, feathers, and flowers. One pet crow even offered a prized slice of roast beef to an ailing canine companion. But there was more.

Leona, from Missouri, routinely receives shards of colored glass in her bird feeder — gifts from wild crows in exchange for sunflower seeds. Gayle had a red-and-white toy bomb dropped beside her by a wild crow. Molly LeMaster, who also talks softly to crows in her yard, has received a small bird wing, a frog leg, a steak bone, a marble, a shiny rock, and a bracelet charm. Barbara Arnold, from Port Townsend, Washington, tenders a box of presents collected from the family of crows that routinely visited and fed in her back yard, including half of a red poker chip, a penny, a paper clip, a red die, bits of colored glass, a nail, a safety pin, colored rubber bands, bits of pottery, a blue glass bead, a red wire twist tie, a tiny pin that says Loyal Legion Week 1933, and, as Barbara quickly adds, the best thing of all — a blue plastic Cap’n Crunch figurine.

Beth, a crow feeder from Seattle, would regularly leave dog kibble for her crow flock by placing the food on the sidewalk as she strolled about her neighborhood. There was no clamor or for the food as each bird would descend separately to pick up its share as she moved along. On one occasion, however, her routine took an unusual turn. Hearing the sound of metal hitting the hard cement behind her, she turned and saw that one of the crows had dropped what seemed to be a bright house key just to the side of the tiny stack of food. The crow took the treat and left the key for Beth. Clearly, the sheer number of independent observations of gifting crows allows us to safely reject the first five hypotheses and concentrate on deciphering whether gifting is intentional or a simple mistake.

There is little in the scientific literature about gifting behavior. Dolphins are known to throw fish to birds and occasionally leave fish for people with whom they closely interact. A variety of birds gather the sorts of objects crows use as gifts. California Condors, for example, deliver bottle caps, pull tabs, and bits of plastic to their nestlings, which they unfortunately eat, and which kills them. Many raptors decorate their nests with fresh greenery, perhaps serving a sanitary or insecticidal role. Ravens often incorporate brightly colored string or wire artifacts into their bulky nests. Evon Zerbetz even reports one industrious pair interlacing welding rods into a nest and feathering the unique structure with Teflon tape, work gloves, screwdrivers, and brightly colored flagging. Male bowerbirds obsessively collect shiny rocks, glass, and plastic to pave their display courts and impress potential mates. And many members of the crow tribe are well known to collect and cache shiny objects. So birds pick up interesting objects, but no scientist has yet reported the connection between a penchant for gathering with a habit of giving to people.

Crows routinely collect and store bright items, so some of these gifts could be simple, unintentional by-products of such an inclination. A crow carrying a shiny object spots an important opportunity to feed, lands on the feeder, drops the item, and because its mouth is full, it cannot regain the item. Opting for the feeding opportunity, it leaves the prize. Gifts placed by accident should often be irrelevant to those receiving the gift, but most people who reported obtaining gifts from crows regularly feed crows. And many of the gifts they obtain were of human origin. On the other hand, people like Nancy, who do not feed crows, also get gifts, and many gifts are natural products like stones, twigs, feathers, and flowers. The evidence is not compelling enough to reject Hypothesis 6, that gifting could be accidental. But if a crow values an accidental gift before eating the food it found, why wouldn’t the crow retrieve that object after eating? Why weren’t gifts stolen by other crows after the crow fed or cached quickly nearby before eating? These nagging questions compelled us to dig deeper into the possibility that crows purposefully leave gifts.

In Arizona, at least one crow seems to have directed his gifts toward an important person. Ornithologist Russell Balda and his wife Judith were startled from an early summer morning to see a crow hanging by its feet, head down on the wooden slats of their fence. They rushed out to free the bird, wrapped it in a calming towel and set it on a rock wall under a large oak tree. The stunned and exhausted bird lay limp for nearly twenty minutes as Judith talked softly to it. A robin, seeing the crow as a threat, dove at the bird, which was jolted back to life and flew off, the irate robin in close pursuit. Later that autumn Judith noticed a crow hanging about the yard and visiting the bird feeder on her deck. Again she talked softly to the bird, and soon gifts started to appear: a dead mouse, regurgitated bits of seed and meat, and sticks. Judith saw the crow leave some items, but others just appeared after the bird had been around. This bird directed its actions at Judith in the place where a crow’s life had been restored. It seems certain that this was the bird Judith rescued, and it also seems that this crow had a crush on Judith. The crow’s actions were not unlike those of a bird courting a potential mate or one repaying a remembered debt to another being.

We are left with two hypotheses that are consistent with the data: Gifting is real, and it may be accidental or intentional. Natural selection could favor purposeful gifting behavior in crows. Gift-giving crows are rewarded by people with protection and food, which improve their survival and reproductive success. Mentally, crows would have no trouble associating a gift with food. Perhaps more stories or controlled experiments will tilt the weight of evidence in favor of either the accidental or intentional possibility.

The above material is from Gifts of the Crow by John Marzluff and Tony Angell, copyright 2012, Free Press.