Mind of the Raven: Investigations and Adventures With Wolf-Birds (10 page)

Raven carrying three robin’s eggs (one in throat pouch)
.

Note:
In 1998 I mastered the ascent to the cliff nest by my home in Vermont, and I repeated the ringing experiment on the three pinfeathered young in that nest. On the first three ringing episodes, spanning 16 hours, I retrieved four boluses of moistened white bread (40 grams), one bolus of pink (calf?) meat (20 grams), and two boluses of not-so-very-fresh liver (45 grams). After that I retrieved nothing in three days (total of 17 hours) that the young continued to be ringed with the pipe cleaners. Nevertheless, they had been fed; they had gained normal weight and never showed signs of hunger. I presume that the parents caught on to what was happening. They had probably devised a new way of feeding (tiny bits rather than boluses?), and I conclude that my graduate advisors had been right; perhaps one should indeed not try to study an animal cleverer than oneself.

Table 4.1 The Main Components of
229 Raven Pellets at Seven Different Locations

R
OA
, K
ONRAD
L
ORENZ’S RAVEN
, raided clotheslines to steal ladies’ underwear. Roa had been exploring a neighbor’s laundry hung on the line just when he was called. He came, taking a small transportable item with him, a pair of panties. When he got a reward of tasty food, he made the association of panties and food. Henceforth, as expected according to classical conditioning theory, he brought these items on his own to redeem them for savory snacks.

It would be difficult to overestimate the importance of learning in the life of ravens. Even so, much of learning involves expression of behavior that is inherited to varying degrees, and released only by specific stimuli at specific times. And as every parent knows, an important aspect of the learning process is simply gaining exposure to what is important. Exposure determines what will, as opposed to what could be, learned. Perhaps the largest part of our educational process, and perhaps also the ravens’, involves mechanisms for gaining exposure to appropriate stimuli. These mechanisms may have several com
ponents. In ravens, youngsters gain the specific experience appropriate for the species’ lifestyle by following their parents. Moreover, curiosity allows them to take advantage of this experience and enhances encounters with relevant objects or things.

I got my first glimpse into the process of how young wild ravens “learn the ropes” by watching the Hills Pond family near my Maine cabin. In early May, when the young birds first left the nest but still remained near it, the adults always came to feed them. Gradually, the young flew to meet the parents when they brought food. Then they followed them. In early June, both parents and their young came near the cabin to feed on carcasses I had left out and to dig for maggots and other insect larvae around them. At that time, the young still begged loudly. The parents picked up food in front of them and transferred the food into their open, yelling mouths. After a few weeks, the parents seemed less attentive to the yelling, and the young sometimes tore off their own meat, or dug with their bills and picked up their own larvae at the decomposed carcass.

It is in the interest of the young to stay with their parents as long as possible, but it is in the parents’ best interest for their offspring to become independent. Conflict is inevitable. In the Hills Pond family, I saw the first signs of such conflict in mid-June. The young flew closely behind their parents, yelling loudly, while the parents erupted in the agitated
kek-kek-kek
calls they make when they are irritated, as when a hawk is close or a predator approaches their nest. These parents did not act pleased, and the young would soon be on their own.

On June 15, 1993, the parents sounded downright oppressed. I saw them coming up the hill once again, accompanied by their noisy youngsters. They descended on the skeletal remains of a calf carcass, but there was no meat left. For a half hour, the family dug in the leaf litter, searching for sylphid beetles and their larvae that were consuming the hide. Later that day, I saw one of the adults flying down along the Wilton-Weld road. This time, two young ravens were chasing along, yelling-begging loudly close to the parent’s tail; but instead of continuing down the road as I expected, the adult bird veered off, dove into the forest, and continued to fly fast through the trees. The
two young stayed close behind. The parent (probably the female) came back out of the trees with them, and landed on the tip-top of a pine, the spot farthest away from any other foothold. Her offspring perched on the first available branch far below and continued their clamor. She made agitation calls, snapping her head nervously in all directions as if searching for a place to escape, then took off down the road again. The two youngsters again screamed loudly right behind. This time, she flew
up
and started to circle. As she gained altitude, she continued to make her agitation calls. Finally, she took off north in a straight line far over Adams Hill, still closely pursued. She seemed to be doing her best to escape her raucous followers, but she did not succeed for long; all three were back at the remains of the calf in the evening.

The offspring, sometimes with one parent and sometimes with both, continued to come up to my clearing at least once a day. They sounded desperate and sometimes pitiful, and the adults acted harassed and agitated. A week later, the two young sometimes came alone. The male parent, who had a leg ring, came several times to feed on a dead woodchuck I had provided. As his offspring begged from him, occasionally he fed them. Sometimes he refused them and cached the meat nearby in the grass instead to let them feed on their own. He had become an indirect provider. The young had been led to food and thereby learned what it looked like. Presumably, they would now find their own woodchuck or some other carcass that they had explored with their parents and recognize it as food at some point.

The family, or parts of it, stayed together most of the time until the end of June. By July 15, they had split up permanently. Single juveniles still came near the cabin in late July, attracted by the begging, when I fed my current young tame birds, who were then still free to roam.

My young ravens behaved with me as I had seen the young of the Hills Pond brood react to their parents. They followed me and showed great interest in anything I contacted. In June and early July, their tendency to follow me was so strong that I had great difficulty escaping them to seek peace and privacy. Even I was starting to make agitation calls! I could not hope to maneuver through the forest like an
adult raven to try to outdistance them, so I resorted to trickery. My usual ploy was to go in the front door of the cabin, and as they gathered at that door, to exit quietly from the rear door and slink away.

Konrad Lorenz observed that young
precocial
birds (those that leave the nest hours after hatching, like ducks and geese), unlike
altricial
birds (which are nearly embryonic at hatching, like ravens), follow their parents soon after they hatch from the egg. Lorenz determined experimentally that they followed whatever they saw at the nest, normally their parents, during a critical, posthatching interval. By this early exposure, they learned their species’ identity, which would later be critical when they identified potential mates.

Is following-behavior like that of the young ravens proof of imprinting? Did the ravens really confuse me with one of their kind? Would they later want to mate with humans as a result? The evidence indicates that they know their own kind very well, despite having followed me. My hand-reared ravens always had as a model not just me, but also others of their own kind. They routinely responded with rapt attention to a raven flying silently in the distance, yet they totally ignored a flying crow, which humans have difficulty distinguishing from a raven. They also responded with the same rapt attention to the ravens’ calls.

I suspect that the exposure young ravens get when they are young probably influences but does not determine sexual preferences in them any more than it does in humans. We wouldn’t, for example, expect a human child raised with a pet gorilla to be sexually attracted to gorillas as an adult. Our preferences can probably be modified, but they cannot be stretched arbitrarily in any and all directions, because we and ravens probably both already have approximate innate concepts, or “templates,” against which we match how an ideal mate looks and acts.

Other things that we and ravens learn are probably less rigidly preprogrammed. Food, for example. There cannot be one innate template of what food should look like, because there is almost no limit to the appearance of what ravens eat. Are there rules for identifying possible food, similar to the “rule” that a duckling follows the first moving
thing it sees after hatching? How do ravens gain exposure to what is relevant to them? If ravens learn about food, how can they possibly begin to gain sufficient exposure to hidden and diverse food, given the almost infinite variety of objects in any environment? Can they afford to pass up anything? If so, what? My four young birds, Fuzz, Goliath, Houdi, and Lefty, were the perfect subjects for a test to find out.

For one month after they left the nest, I led the four birds at least once and sometimes several times a day on thirty-minute walks. During these walks, I wrote down everything in their environment they pecked at. In the first sessions, I tried to be teacher. I touched specific objects—sticks, moss, rocks—and nothing that I touched remained untouched by them. They came to investigate what I had investigated, leading me to assume that young birds are aided in learning to identify food from the parents’ example. They also, however, contacted almost everything else that lay directly in their own paths. They soon became more independent by taking their own routes near mine. Even while walking along on their own, they pulled at leaves, grass stems, flowers, bark, pine needles, seeds, cones, clods of earth, and other objects they encountered. I wrote all this down, converting it to numbers. After they were thoroughly familiar with the background objects in these woods and started to ignore them, I seeded the path we would later walk together with objects they had never before encountered. Some of these were conspicuous food items: raspberries, dead mealworm beetles, and cooked corn kernels. Others were conspicuous and inedible: pebbles, glass chips, red winterberries. Still others were such highly cryptic foods as encased caddisfly larvae and moth cocoons. The results were dramatic.

The four young birds on our daily walks contacted all new objects preferentially. They picked them out at a rate of up to tens of thousands of times greater than background or previously contacted objects. The main initial criterion for pecking or picking anything up was its novelty. In subsequent trials, when the previously novel items were edible, they became preferred and the inedible objects became “background” items, just like the leaves, grass, and pebbles, even if they were highly conspicuous. These experiments showed that ravens’
curiosity
ensures exposure to all or almost all items in the environment. I never saw them pass up
anything
that was new to them.

In the field, food items are locally distributed: Cranberries grow on the tops of mountains and in bogs, raspberries in clearcuts, wild strawberries in fields, and so on. Therefore, in the context of their own curiosity, the following-behavior (taking advantage of their parents’ experience) ensured that odd and perhaps rare sorts of food would always be found. This elegant mechanism would result in food-finding in any environment, with any kind of food, and it explains another long-standing enigma—the ravens’ well-known strong attraction to jewelry and other rare baubles.

George Miksch Sutton, the famous bird artist and Cornell ornithologist, said half a century ago that his pet raven “was an aesthete. His love of baubles was not wholly carnal” because he did not eat them. But Goliath and the others treated even pine cones like baubles for the first day or two out of the nest. They soon got their measure of pine cones, and forever ignored them. Having determined they were not food, they soon got bored. So it went with dandelion flowers, maple samaras, cigarette butts, pebbles, shiny bits of glass, inedible winterberries. Blueberries?
Those
“baubles” tasted good, and were
not
soon forgotten. Rings and coins? The birds’ immediate attraction to such items was undoubtedly aesthetic, but in an ultimate evolutionary sense the question is,
why
were they aesthetic to them? And the answer is, because of the carnal reward; they
represent
new things, some of which
can
be good food and so they are examined in play. If the birds were attracted to objects merely because they were already
known
to be good food, then what they already knew would be known even better, but nothing would be discovered.

The same “carnal” tendency of ravens also sheds some light on Lorenz’s anecdote about the ladies’ underwear. Since young ravens are attracted to anything that stands out within their environment, laundry hanging on the line is obviously a prime attraction. When I was still a graduate student at UCLA, my first pair of ravens made themselves unpopular with my mother when I brought them home to Maine. They pulled clothespins off the line and either scattered the
laundry or left dirty tracks on those clothes that they left hanging. In retrospect, I understand—the birds had shown interest in what had interested
her
, as well as in what was novel to them. Like picking up shiny new pebbles, picking off clothespins is play. If they carried things away, their plunder was generally the lighter, smaller items, like socks, and of course, ladies’ underwear.

A simple experiment proved that the ravens’ strong curiosity to explore contrasting or novel objects in their environment functions ultimately in food-finding. Having taken a trip to the seashore, where I behaved like a young raven myself by picking up a large collection of strange new trinkets, I brought my four young charges bags full of such different items as beach-worn pebbles, seashells, crab claws, and seaweed. I included only one potentially edible item—small dead sand crabs, something Maine inland ravens never get to see, much less taste. When Fuzz, Goliath, Lefty, and Houdi were confronted with all of these seashore items at once, which I had strewn through a walkway in the aviary in the forest, they became highly animated and sampled them all indiscriminately. Within ten minutes, they were already focusing on the sand crabs and starting to get bored with the rest. After making only several contacts with these munchies, they sought them out. Within thirty minutes, they had found and eaten every one. By the next day, they basically ignored all of the other inedible trinkets. They had become like Jakob, Klaus Morkramer’s raven, who could be trusted even with the expensive Roman antiquities because they bored him.