A pair or pairs came by repeatedly, and each time, they seemed to be chased off with greater vehemence. Goliath took off after them even when Whitefeather was far away foraging, an indication to me that strangers are apparently identified even from a distance.
The strangers that kept coming by were not merely interested in food. I once had a deer carcass plainly visible in the field when two ravens came flying very high in tight formation from the east, the direction of the nearest nesting pair at Hills Pond. They flew over and beyond the carcass and zoomed straight down toward Goliath and Whitefeather’s nest instead. Goliath and Whitefeather both took chase. It was one of the most vehement chases I’d ever seen, lasting for at least twenty minutes. I heard honks, knocking, begging, rap-rap-raps, undulating quorks, caulks, rasping quorks, agitation calls. All the while, the intruding pair kept trying to come back to the aviary, but Goliath and Whitefeather continued to hold them off. Did the intruders want to destroy the nest and/or young?
After a while, the neighbors apparently realized that the new pair on the hill, Goliath and Whitefeather, could not be driven off. They stopped coming, but shouting matches between them continued daily. Whenever one of a neighboring pair made their territorial advertising calls from their nest area, Goliath and Whitefeather faced in their direction and responded with ear-shattering territorial calls of their own. At no time did a raven come by when these calls were given.
In early June, Goliath and Whitefeather led their young all around the neighborhood, visiting the many different carcasses I had spread out. At that time, the young still begged from their parents. A parent would tear off meat, then feed it directly to a nearby begging youngster. Later, the young started tearing off some of their own meat, and the parents began treating their offspring as competition. Goliath, who had been the main provider until then, sometimes even ferociously pecked at them.
On September 17, 1996, shortly after Goliath and Whitefeather returned after a long absence following their raising of young, I heard a raven calling from the area of Hills Pond. Goliath, who was as usual perched on the tall dead birch stub next to us just above the fire pit, turned attentively to look in that direction. Strangely, he was neither excited nor defensive. Minutes later, both Goliath and Whitefeather took off and began soaring. A raven flew up from where we’d heard the calling, and joined them. All three circled amicably together, far above the clearing. They circled close to each other, freely intermingling, so that it was no longer possible for me to distinguish them. After five minutes of socializing, the newcomer broke off and flew back to where it had come from, and Goliath and Whitefeather returned to our hill. Goliath was in a playful mood. On his descent, he did two complete corkscrew tumbles. These were the first such aerobatics I’d seen him do. Then I heard a rush of air as he came down at 45 degrees, suddenly dove straight down, and did three corkscrew twists before landing gracefully beside his mate.
The next morning, the pair was again soaring over the hill with a third raven. A sharp-shinned hawk rose to meet them, diving at one of them. One raven flipped onto its back and extended its feet, and the hawk flew on. The other raven returned to its territory down by Hills Pond. Another pair flew over at great altitude, which Goliath and Whitefeather ignored. In late afternoon, a group of eight ravens came from the north. Goliath and Whitefeather ignored them, too. Did they have specific friends?
On September 28, Goliath was flying with another bird just above him, the two moving in perfect synchrony, a perfect pair. Whitefeather was near me, seemingly unconcerned. The flying pair stayed circling over the valley and the pine-clad hill near the cabin. The only calls I heard during the fifteen minutes that the two flew together were the caulk calls, which to me sound relaxed, friendly, and reassuring. I often hear these calls when Goliath and Whitefeather are together alone. After the flight, the third raven flew north, and Goliath came back to the cabin and his mate.
It rained on October 28, but in early afternoon the rain stopped, the fog lifted, and dark clouds drifted from the northwest. The air was clear, and I could see to the tops of all the surrounding hills. Near 2:20 P.M., I suddenly heard the rap-rap-rap calls from Goliath and Whitefeather by the aviary. Had they seen a stranger? I walked out of the cabin and faintly heard a raven in the distance to the northeast making the rap-rap-rap calls. Goliath launched himself instantly and flew toward it, but then doubled back to land on a maple near the cabin after making a large circle. He continued to look in the direction of the other raven, standing tall, erecting his “ears” and rubbing his bill vigorously on his perch in an exaggerated display of power. In the distance, the raven called again. Again, Goliath took off instantly after it called, then all was quiet. Five minutes later, I heard the caulk calls and saw two ravens flying around the hill by the aviary. Was one Goliath? A moment later, I heard the knocking calls. Then I saw four ravens coming up the hill. There were no chases, no antagonistic interactions. The two lead birds were Goliath and Whitefeather. They swung off and landed near their usual perches on the hill, while the other two birds turned around and went back down the hill, toward the east where Goliath had flown, apparently agitated, a few minutes earlier.
Although the data on distribution of nest sites is congruent with the concept of exclusive defended territories, I suspect now that raven society is far more complex. My observations of Goliath and Whitefeather suggested that adult birds differentiate and discriminate between friends and foes. Since aggressiveness is a function of food supply as well, I wondered if the conflict between vagrants and territorial residents was really between familiar versus unfamiliar birds rather than juveniles versus adults.
I had not answered my earlier question about why there were three birds at the nest on the other side of the lake, but I was no longer surprised that such things could happen. I had learned that raven partnerships are flexible, with sexual activity and jealousies possibly confined to a very narrow time slot at the time of egg-laying.
Many of the behaviors associated with nesting are primed by hormones, but as in all other birds and also in us, the complexity of response indicates that the birds’ minds are driven by more than just hormones. The relationships within and between pairs and with other ravens could suggest that these birds evaluate and make choices.
A pair of courting wild ravens within a crowd. The male is striking his “macho” pose. The female (at right) is doing her knocking display, which includes winking with her white nictating membrane.
TEN
Pairs as Cooperative Teams and Sharing
OLD PREJUDICES ARE HARD TO change. I had until then long cherished an image of the raven perched on a lofty crag surveying its domain and reflexly chasing out all others that cross its skies. That image is not necessarily a false one, but it is only one dimension of a multidimensional picture.
Goliath and Whitefeather and my other tame ravens had given me glimpses of another dimension to the raven’s social life that I had not suspected. I began to suspect that ravens, aside from being cantankerous loners that were intolerant of others, could also form strong attachments to others. Perhaps their superb flight capacities even allowed them to maintain friendly contact with neighbors in a loose confederation, like that more typical in other corvids.
Ravens do not usually breed until their third or a later year of life, yet already in their first fall, Goliath and many other ravens I have kept began to form strong partnerships. In the field, such partnerships would be difficult to detect, although in crowds of juveniles performing aerial dances, pairs predominate. The problem is that we have no way of knowing if these pairs last for a moment, an hour, a day, or a lifetime. Ravens, like humans, are exceptional animals that may pair up as friends years before breeding. My observations with aviary birds shows that some of the friendships last and others don’t. In the wild, adult ravens probably stay paired up the entire year, not just when rearing young. Raven pairs fly around together in the daytime, sleep close to each other at night, regularly communicate w
ith each other, and mutually preen each other.
Could the pairing result in cooperative hunting partnerships? Economics provides a rationale for raven’s gregariousness in communal roosts, since the birds who join roosts are led to carcasses that others of that group have found. Are there also economic reasons for both raven subadults and adults to pair up? Might couples work together in mutually productive partnerships, because a couple could get more food than either of the two could get independently?
Wildlife filmmaker Jeff Turner photographed ravens at sea cliff colonies of murres and kittiwakes at Cape Pierce, Alaska, in the spring of 1997, and described seeing a raven “dive like a hawk and hit a kittiwake in the air. White feathers flew! This raven was unable to grab the kittiwake on this occasion, but I saw ravens plucking fresh kittiwakes every day. Usually only one raven dove and hit a kittiwake again and again, eventually forcing it onto the ground when it and others jumped on it and killed it. The ravens often worked in pairs. We also saw them go up to kittiwakes on the nest, grab a wing and yank them off, then they or a partner rushed in and took eggs.” John R. Moran, an ornithologist, saw groups of ravens at the same site attacking and killing large gulls and geese.
Hunting behavior of ravens could be more efficient when two or more work together rather than alone, and numerous anecdotes indicate that ravens indeed hunt effectively in teams. Take squirrel hunting, for example. A squirrel on a tree can easily escape almost any pursuer either by running to another side of the tree, or going up or down the tree, depending on the direction of the pursuer. If a mobile hunting partner could position itself in the path of the escaping squirrel, the retreating animal would be cut off from its escape route. Gary Keene, an observer from Maine, saw something resembling this behavior: one raven chasing a gray squirrel across the road while another awaited on the other side.
The most commonly observed raven teamwork has been of ravens taking prey away from predators. Wildlife biologist George Schaller told me of watching raven pairs in Mongolia cooperate in snatching rats from feeding raptors. Similarly, in Yellowstone Park, Ray Paunovich reported seeing a red-tailed hawk with a ground squirrel. Two ravens approached. One distracted the hawk from the front while the other handily snatched the squirrel from behind. Carsten Hinnerichs saw the same maneuver repeated three times in a row in a field near Brück, Germany, where a fox was catching field mice. Terry McEneaney, Yellowstone Park ornithologist, observed two ravens circling an osprey nest where the female osprey was incubating. One raven landed on the nest rim and took a fish, then while the osprey was distracted by this thief, the other raven swooped down and stole an osprey egg.
Vermont naturalist Ted Levin saw a similar type of opportunism in raven pairs raiding the nests of whimbrels on the tundra near Churchill, Manitoba. One raven would flush the bird from the nest while the other snatched eggs. Wisconsin ornithologist and Arctic explorer Ludwig Kumlien saw raven pairs succeed in killing young seals that lay basking near their ice holes. One raven would at first leisurely circle over the seal, then drop down beside the seal’s escape hole in the ice. The raven’s partner then drove the seal to the hole, where the first raven killed it by pecking it on the head.
David Hatch reported in the Winnipeg Free Press (December 19, 1992) watching four common eider ducks on the Hudson Bay near Churchill while he was eating lunch with a group of tourists in a tundra buggy. “Two ravens landed within a few meters of the eiders—the eiders were alarmed but after five minutes settled down, burying their heads in the feathers on their back. Suddenly one raven made four or five large hops toward them—and drove its bill into the eider’s eye—both ravens then continued the relentless attacks on the eider’s head and within a minute the eider was dead.”
Was planning involved in the teamwork? An anecdote reported to me by Professor Dieter Wallenschläger, a biologist at the University of Potsdam, seems to suggest that it is sometimes possible. Wallenschläger saw a pair of ravens on the Island of Werda in the Baltic Sea attacking a mute swan incubating its eggs. The swan hissed and lunged, but stayed on its eggs. If the swan did not budge from its eggs, the raven’s attempt would fail. One of the ravens did something unprecedented. It feigned injury, dragging a wing as plovers do routinely when leading a predator off its nest. The swan lunged after the seemingly crippled raven, and its mate rushed in and took an egg. Feigning injury as such is not remarkable. A great many, if not all, shorebirds and innumerable other ground-nesting birds do it. But in them it is likely an at least partially or largely programmed response. That argument can’t be made for the same behavior in ravens, especially when it is used in a totally different context and where it serves a totally different purpose.
A raven pair, with the the male (at right) in self-aggrandizing display.
In all of the above instances, there is no proof that the ravens anticipated the consequences of their actions and behaved in a conscious way in mutually agreed-upon plans. For the most part, there is no necessity to invoke such a scenario, but neither can it be excluded. The simplest hypothesis is not necessarily the right one. Indeed, there can be considerable debate on what the simplest hypothesis may be. My own bias is towards the idea that the cooperation displayed by these anecdotes does not usually involve planning and forethought, for the simple reason that in most cases planning may not be needed, although that logic is somewhat forced in the examples of the ravens and the swan.
According to some views, the birds are not cooperating if they each seek only to satisfy their own chances of success without a conscious regard for the other. From an ecological-evolutionary perspective, however, the effect is critical and intent is irrelevant, the latter being another question altogether. Cooperation might occur whether it is intended or not. What matters for practical cooperation is payoff. The question boils down to whether just one bird of a partnership feeds on the spoils that the second bird, by its chasing, blocking, or distracting, has helped to get.
To that question we do have an answer, and that answer is derived from observations in the aviary. First, I found that the raven partnerships can indeed last years, and as previously supposed mated pairing appears to be almost irreversible. Furthermore, mutual tolerances among partners ensure that food secured or held by one is also available to the other; food is not defended against partners. Therefore, from the standpoint of evolutionary ecology pairs cooperate, while from that of psychology they may not, but could.
I examined the power of pairs in detail in thousands of interactions with my group of six birds, when all were about two years old. In this group, Blue was a male and the undisputed dominant of the group. The birds probably wouldn’t nest for another year, but Blue had already paired with a female, Red, a year earlier. All six birds normally got along amicably, but if they were hungry and I gave them a choice hunk of food like a calf haunch or a woodchuck carcass, Blue immediately perched on top of it and began to feed, excluding all others except for his partner. A year earlier, he still had excluded her mildly, but for only a short while. Now, he immediately let her feed beside him, even at the choicest meat. The “rule” was: Blue feeds first and he chases others off. The exception was if the food was feared, in which case he waited until subordinates “tested” the food and started to feed; then he chased them off. His mate, Red, was highly subordinate to almost all the other birds, but she joined him at all times and fed at his side, regardless of the presence of others. He chased off all others that dared to come near him, and since she fed right next to him, she effectively fed unmolested under the umbrella of his protection. When on one occasion I removed him, she received attacks from the others above her in the hierarchy, and she had to contend with them herself. At that point in their relationship, he did not bring her food. By the time they begin to nest, however, he would feed her as he would his nestlings. What one would catch both would eat, and together they would become even better providers for their young and for each other than if they were alone.
Raven feeding on beef suet.
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ELEVEN
Hunting and Foraging
THE PASSERINE, OR PERCHING BIRDS, the group that ravens belong to, are characterized by species-specific, largely innate, or “hardwired” foraging specializations. Ravens are unique passerines, not only because they are large meat-eaters that lack the physical toolkit of raptors, but also because they are opportunistic generalists that can feed on almost anything from fresh carcasses and the insects feeding on rotten carcasses, to tomatoes, Cheetos, and dog droppings. Even more impressive than their flexibility are the many ingenious techniques they have been observed using to get their food. These methods are not the ways of all ravens, because many raven individuals are unique and any one person observing them can hope to see only a very small portion of the species’ amazing repertoire of behaviors.
Mind of the Raven: Investigations and Adventures With Wolf-Birds Page 16
