The next day, eight crows and the raven were back, behaving like the day before.
On April 11, after I had been away for a few days the calf carcass hosted not only five crows, a turkey vulture, and two broad-winged hawks, but also one coyote. The latter left just as it was getting light, before the birds arrived.
Again, the crows flew up and did not feed when the ravens fed, but the crows fed amicably and without sign of alarm or caution directly alongside both hawk and vulture. The second hawk waited its turn perched in a tree, and fed only after the first had left. As always before, the raven took precedence over all. It unhesitatingly came down to feed regardless of whether a hawk was on the meat or on the neighboring tree; but when it fed, no crow, singly or in a crowd, ventured near this male raven. The raven never bothered to nip the tails of the hawks or the vulture next to it.
Ravens are well known to pull the tails of raptors near baits. Their reason for doing so is obscure, but their effects on the raptors are clearer, though varied. In northern Arizona, recently released captive-reared California condors, Gymnogyps californianus, are provided with animal carcasses to feed on. Quite often, the condors are flushed from this food when golden eagles appear, and they may not come back for days. However, Amy Nichols, working for the Peregrine Fund on the condor project, reports that although ravens may “continuously torment the condors by pulling relentlessly at their feathers,” they also viciously mob any golden eagle that comes near. The eagles retreat from the ravens, giving the condors time to feed, while the condors are not displaced from the carcass by the ravens.
Ravens do not normally interact with chickens, but naive ravens may have no way of distinguishing them from eagles. What might they do with them? Our neighbor had a dozen Rhode Island Reds, each weighing almost twice as much as a raven, and I had my group of six ravens, six months in age. The chickens were past laying age, which is why my neighbor donated them in the name of science. She didn’t want to kill, pluck, clean, cook, and eat them herself. After I had tried one, I knew why. My ravens had hardier palates. They liked the first broiled chicken meat just fine. Before I planned to give them the rest raw, I decided first to find out how they would respond to them live.
When the first two chickens were let out of the burlap bag I’d brought them in, they cackled excitedly, walked slowly and deliberately, and seemed unconcerned about a mere six ravens that happened to gather round. The ravens started edging closer, walking sideways and crouching, enabling them to make an instant retreat, which they did whenever a chicken as much as took one step toward them. Within an hour, some of the ravens got bolder, managing to sneak up occasionally to yank on a tail feather. If a chicken ran, the raven hopped comically behind the cackling hen. Soon the ravens were interrupting their usual play with sticks and other objects to “count coup” with chickens. This activity continued almost ceaselessly for the whole day. Except for losing a few tail feathers, no harm was done to the chickens. The ravens became ever more disinterested and the hens became ever more nonchalant. Before two days had passed, they were feeding alongside the ravens on a calf carcass. The ravens ignored them, making no attempt to chase them off “their” carcass, although they were often intolerant of each other.
To find out if the ravens became habituated to chickens in general, or just to these particular individuals, I replaced the first pair with two others. A new Rhode Island Red I released into the aviary at night seemed to be quite excited when it woke up the next morning to find ravens flying all around. This bird panicked, and it was briefly “tested” by the ravens as the other two had been initially. All the other hens I later provided were totally ignored.
The rooster was next—a robust black and white Plymouth with a brilliant red comb and wattles and a thick neck. He stood so tall, you’d think he would have toppled when I let him out of the bag. He spread his shoulders, flapped his wings, crowed six times, then ran to the hens. The ravens were unimpressed. They continued to play with sticks. The rooster acted as if the ravens weren’t there. Whenever he happened to walk near a raven, it scuttled or flew away. No raven “tested” him as they had the first two hens. Nor did they approach another confident chicken, a buff Orkinton. Had they generalized, realizing that despite their superficial differences, they were all just chickens?
I left one chicken in the aviary with the ravens for a month. The ravens always yielded to her, and never even tweaked her tail. Whenever food was provided that she and the ravens wanted, she walked up to it and they briefly scattered. This is not exactly the behavior one might expect of ravens, who boldly pull eagles’ and wolves’ tails, chase golden eagles, and feed among wolves at the kill.
Several months later, I provided them with two new Rhode Island Reds who were the same size and appearance as the others, but who were still young. One acted unsure of herself. The ravens drew closer. She panicked, and then all the ravens attacked her relentlessly. After two minutes and an apparent imminent slaughter, I felt obliged to remove her. Like an ostrich sticking its head in the sand, she had sought refuge by sticking her head behind a loose board. The other chicken, who was a highly confident individual, fed alongside them and was ignored.
The next trial was with an adult turkey of wild-type coloration. The huge bird, seeing the ravens, fluffed out to make herself look even bigger, fanned her huge tail wide, and while holding her head horizontal, hissed and walked slowly and deliberately. The six ravens couldn’t resist. In the first thirty minutes, they tweaked her tail a total of sixty-two times. I sampled four more half-hour periods over the same and the next day that I allowed the turkey to stay with them. The total tail-pulling contacts per half hour steadily dropped from sixty-one to forty-six, twenty-eight, sixteen, and then to two. Two ravens contacted the turkey forty times each, while one bird did so only once. Together, the six ravens snagged only about a dozen tail feathers.
On May 16, I presented them with a fat, brown-backed, calm, and confident gander. The six ravens immediately came off their perches to surround the goose. All were silent. They tried to sneak up on his rear, but the gander turned. All jumped back. One raven finally nipped at his tail. As the gander made a feint at her, her mate rushed in and also yanked the goose’s tail, but that was all that happened. In fifteen minutes, all the ravens had lost interest and wandered off. When I later let a tame Canada goose they knew well into their aviary—it had for two months wandered to the edge of their aviary—they attacked it vigorously at once. As with the unsure hen, I feared for its life and quickly removed it from them.
Their next meeting was with Murphy, my daughter’s lively, wolf-colored German shepherd. The dog was treated with considerably more respect than the fowl, but with at least as much interest. At first, the ravens made high-pitched, upward-inflected alarm calls. But Murphy paid no attention. She sniffed all around and within seconds settled down to chew on a frozen calf as all six ravens swirled around her. The birds were excited, squeezing out one fecal dropping after another, which kept getting smaller with each one. Within a minute or two, all of the ravens except White had flown out through the open door and into the side aviary to perch safely and silently up on the high perches in their shed. White, the normally totally silent bird who was at the very bottom of the dominance hierarchy of this group of ravens, behaved entirely differently. Not only did she stay to watch Murphy intently, but she also kept following the dog, and she swooped over the dog repeatedly, making rasping calls. Blue, the undisputed large dominant male, continued to cower silently up under the protective shed in the adjoining aviary, along with the others. Within minutes, White’s vociferations grew louder. Soon they were deafening and she became ever more animated! She not only chose to stay in the same aviary with the large dog, but she began an extraordinary display I had never seen her do before, which was out of character with her otherwise meek postures and demeanor. She stood tall, held her bill high, erected her ear feathers (a display of power and dominance), fluffed out her throat and spread her shoulders (
also parts of the dominance display); then she backed up these postures and feather displays with an amazing range of vocalizations in an endless spirited, loud monologue, an unbroken series of long trills, loud yells, high, rapid series of yips that switched now and then to low, rumbling, rasping growls. The sounds ranged back and forth from squeaks, so high in pitch that her voice broke, to low, deep, rumbling sounds. All of this was accompanied by wildly gesticulating head and wings. Every few minutes, she stopped for a few seconds to swoop once more over the dog’s back, making uniformly deep, long, rasping calls, the same kind the birds make when confronting any strange animals, and sometimes also strange ravens. Her animated behavior startled me, because she had been almost silent for months. She also had never acted “macho” before. She had changed from a wallflower to an engaging, happy, confident, and powerful personality. I doubt that the display was for the dog, though; perhaps she realized that she was alone, and that the others would keep their distance.
After four separate ten-minute sessions of Murphy in the aviary, none of the ravens had come close enough to yank tail, as a previous group of much younger ravens did within a minute or two to an old, lame husky I had introduced to them.
My experiments with barnyard fowl and household pets may seem inconsequential, but they were informative. They showed that ravens go to some lengths to try to get acquainted with strange large creatures they don’t know. After they get to know them, they either ignore them or try to kill them. Knowing this, however, is no substitute for seeing what actually happens in the field, where the real test comes as they face big, fierce carnivores.
I had made plans years earlier to travel to Yellowstone Park and to Oregon, where colleagues had kindly volunteered to set up carcasses for me to watch wild ravens interacting with naturally occurring competitors and carnivores. Wolves had not yet been reintroduced to Yellowstone, but coyotes there (unlike in Maine) were diurnal, and I was curious how they interacted with ravens. Unfortunately, when it came time to use my airline ticket, I had reached a critical point in a radio-tracking experiment and was unable to leave without putting this ongoing work into jeopardy. However, I found an eager volunteer, Delia Kaye, who gladly accepted the challenge to be my emissary, with the understanding that she would take extensive notes.
Delia went to Yellowstone Park in mid-February 1992, where she was hosted by John Williams, whose team of researchers was studying the pack behavior of coyotes. The park ravens were not food-stressed. As is usual near the end of winter when ravens begin breeding, there were winter-kill elk carcasses all around. These were so abundant that many had no ravens feeding from them at all. The birds apparently preferred only the freshest, just-opened carcasses.
Delia was on hand to see one pack of coyotes begin to tear into a bull elk that had just died. Within several minutes after the coyotes had torn a hole into the neck, two ravens arrived and started feeding as well. The coyotes occasionally lunged at the ravens, but the birds merely jumped aside and came right back. Most of the time, the ravens, whose numbers quickly increased to about a dozen, fed unmolested with the coyotes nearby. The birds seemed surprisingly relaxed in the company of the coyotes.
In Eastern Oregon, the situation was entirely different. Gary Clowers, our host there, had set out a deer carcass near Grandview on the eastern base of the Cascade Mountains. From a blind made near this carcass, Gary and Delia kept watch for four days. No coyotes came, but as many as twenty-six ravens were present at a time. Unlike at Yellowstone but much like in Maine, these birds did not quickly descend to the opened carcass. Instead, they loitered about in the vicinity, acting fearful of the unattended carcass.
Typically, all the ravens assembled on the ground about ten to fifteen yards from the carcass, then started to approach it as a group. Coming closer, two or three birds might haltingly edge toward the carcass, drawing others behind them. Then they would all jump back again and fly off. As in Maine, whenever they drew near the carcass, they walked hesitatingly, opening their bills in fright and performing what looked like numerous jumping jacks. Even on the fourth day, with twenty ravens routinely near the carcass, only two individuals approached it close enough to feed. These results were almost precisely as those I was used to seeing in Maine. But there was a big difference. Instead of all of the crowd eventually ending up at the carcass, most of the ravens got their meat without ever needing to go near the carcass they feared. They used intermediaries. The dozen or so magpies at the site showed no hesitation about feeding from the carcass. Neither did four eagles (two immature and one adult bald, and one immature golden). The eagles freely walked up to the carcass to feed, showing no hesitation at all. As a magpie, raven, or eagle left with meat, members of the timid raven crowd would take up a chase. Only birds leaving the carcass with food were chased. Up to four ravens might chase a single eagle or magpie. Magpies quickly dropped their prize when pursued by ravens, but whether all the eagles dropped their food could not be determined since the eagle-chases went far out over the countryside.
In New England, there are no magpies, and eagles are rare. Blue jays and crows, unlike magpies, don’t come near a carcass with ravens. The strategy of stealing food from intermediaries rather than approaching a feared carcass is less effective in Maine, but I have on numerous occasions seen ravens that have secured a piece of meat, when chased by other ravens, drop their meat routinely to terminate the chase. At dumps gulls are similarly chased by ravens until they give up their food morsels.
Along the Maine coast, bald eagles were fed at supplemental feeding stations for several years to prevent them from migrating south and becoming contaminated with pesticides. These feeding stations became prime raven magnets, attracting huge crowds of them. The ravens did not ignore the rare eagles. They treated them as my young aviary birds had treated the chickens and turkey when they first met them—they edged up behind them to yank their tail feathers. Were they trying to tell them something, discourage competition, find out something, or impress potential mates with their daring? There were hints here that the ravens’ lives are interdependent with other animals at and around carcasses, although I did not yet suspect the true relevance of these interactions.
A still-young Goliath (note light-colored mouth) play-vocalizing (i.e., “singing”) to himself. His feather and body postures reflect a confident, self-assertive mood. He had, at this time, already lost most of his tongue in a fight with Fuzz.
SIXTEEN
Vocal Communication
COMMUNICATION CHANNELS IN THE animal world include those of touch, sound, sight, and scent. Electric eels even use electric pulses. Insects communicate their sexual readiness and their location by scents, sounds, and movements. In our social interactions, we communicate all sorts of information unconsciously, using our eyes, gestures, tone of voice, and facial expressions. Ravens also are very expressive. By a combination of voice, patterns of feather erection, and body posture, ravens communicate so clearly that an experienced observer can identify anger, affection, hunger, curiosity, playfulness, fright, boldness, and (rarely) depression. The ravens’ calls have one basic message, which is to draw attention to themselves. Beyond that, they also indicate functions: feed me, stay away, come here, recognition. Increasing specificity comes from context. The specific calls are not used as language. Ravens don’t have calls symbolizing carcass, eat, come, meat, et cetera. Ravens can’t say, “Come with me to that carcass to eat some meat.” Such communication implies complex thoughts. Ravens don’t think with words. If they think, it is with images, as we do when we don’t use words; but the basic logic of communication remains.
As an example of the logic of communication, let us reconsider a simple case: the loud begging cries of young ravens. The begging is understood by the parent to mean that the young need to be fed. Of course, the young can “lie”—in their competition with one another, they can try to outshout the others to get more than their fair share. I mean this in an unconscious sense, because I’m referring to evolut
ionary logic. A high cost of that loud begging could be the attraction of predators who would eat them. That would be information transfer to predators, but not communication. Information transfer occurs between young and parents, and in that case there is communication, because both signaler and receiver benefit. But the costs and benefits to the participants may vary, and evolution within both participants acts to minimize costs. Why raven young are especially noisy relative to most other young birds can be seen from the “experiments” that evolution has conducted over millions of years. We find, for example, that young woodpeckers safely ensconced inside fortresses of solid wood are even noisier for their size than ravens. Young woodpeckers make a din that scarcely ever stops, whereas the young of all ground-nesting birds, who are extremely vulnerable to predators, are almost totally silent except for the few peeps they make at the precise moment that a parent visits the nest with food. We can conclude, therefore, that young ravens, like young woodpeckers, are proximally noisy because they are hungry, and ultimately very noisy because of their relative safety in their hard-to-reach nests. There is little cost to their being loudmouthed; they can “lie” and act as if they are starving when they merely have an appetite. No mental awareness is implied in any step of this process.
The communication described above conforms to the theory called the Handicap Principle, as promoted by Israeli biologist Amotz Zahavi. Much of animal signaling makes sense according to this theory. It says that in order to be effective, signals must be reliable. And in order for the receiver to know they are reliable—for the receiver to treat them seriously—they must be costly to make, for example, by attracting predators. If they were not costly to make, then signalers could “cheat” or give false information. This logic, however, is not always easy to apply to ravens’ vocalizations, as the following examples suggest.
Mind of the Raven: Investigations and Adventures With Wolf-Birds Page 22