All of the ravens I have raised from nestlings started out catching crawling insects and other invertebrates (noticeably exclusive of angle worms, which they disdain). Then they went on to larger prey, the only apparent requirement being that they could catch it. There are many published anecdotes of the raven’s predatory exploits. They include attacks on reindeer (Ostbye, 1969), lambs (Hewson, 1984), and seal pups (Lydersen and Smith). But most of the reported predations are on other birds, including grouse (Allen and Allen, 1986), seabirds, and common pigeons (see Notes and References). The prey is often struck in midair (Elkins, 1964; Schmidt-Koenig and Prinzinger, 1992; Jensen, 1991).
I have never personally observed a raven catch a bird in the wild, but I once surprised Goliath in the woods just as he was plucking a blue jay. There was fresh blood on the jay’s feathers. The bird had bled, so Goliath could not have found it already dead. I could not imagine how he might alone have outmaneuvered a jay in the woods. I also found a raven pellet consisting entirely of the fur and bones of a flying squirrel. One single pellet contained skulls of three moles! On another occasion, I found a gray squirrel skin lying on the ground under Goliath’s favorite perch. The fresh skin had leg bones still attached and unbroken, and on the right hind leg the skin had a bright red spot, a blood bruise. There was another hematoma on the skin from between the eyes. This squirrel apparently had been pecked on the leg and the head with a sharp object before it had died. It was not a roadkill.
Adam Farrington, a raven-watcher from Poland, Maine, witnessed a raven’s attack on a red squirrel. Walking in a pine grove to examine a raven’s nest, Adam suddenly saw a raven diving and crashing through the branches in the manner of a goshawk, to pounce on a red squirrel. It knocked the squirrel out of the tree, and pursued. By then, the raven was close to Adam on the ground, and veered off and aborted its attack. Near the same area, Adam also saw a raven apparently clutching a thick tree trunk. The bird had its wings stretched out to the sides around the tree, blocking a tree hole where a squirrel had sought refuge. As long as the pursued animal remained inside the tree hole, it would be safe, because ravens cannot chip solid wood with their bills like woodpeckers. They can, however, use their bills to excavate soil. I received one report of a raven digging up a ground squirrel in Colorado, numerous reports of ravens on Maine islands digging petrels from their nesting burrows, and one report of ravens digging bank swallow nests out of their tunnels in sandbanks along Alaska’s Kenai River.
The open country of Yellowstone Park affords good visibility for witnessing ravens’ foraging activities. On April 17, 1987, Terry McEneaney saw ravens trout fishing. A pair of ravens caught, killed, and cached a total of twelve cutthroat trout. The two ravens fished by standing on a sandbar of a tributary of the Yellowstone River in the Hayden Valley. When a trout ascended a riffle of the creek, one raven would wade out into the water, grab the fish by its dorsal fin, and pull it onto the sandbar. There it would kill the fish by pounding it with its bill, and fly off with it into the sagebrush to cache it out of sight.
Fish are sometimes caught through the use of intermediaries. Bob Landis, also in Yellowstone Park, filmed a raven catching a cutthroat trout in a somewhat circuitous manner. An otter had caught the trout in the river, and as it took the fish out of the water to eat it, a bald eagle stole it away and perched to start to eat it. A raven, seeing this as its opportunity, came and harassed the eagle by yanking its tail feathers. The startled eagle turned toward the raven, momentarily letting go of the fish, and the raven rushed in and took the trout.
The previous example could show the vagaries and sheer luck involved in trout fishing. However, as is usually the case, the raven made the best of it. Luck is seldom as haphazard as it may seem. It means being at the right place at the right time, and most of all, it means being prepared to take advantage of opportunities.
Sometimes ravens force their luck, as the following observations by Terry Goodhue and John Drury illustrate. The two biologists had much opportunity to watch ravens on Seal Island off the coast of Maine during their years of implementing and studying the resettling of puffins there. The island is barren of trees, about a mile long, and twenty-five miles off shore. It is the home of one pair of ravens, who nest there in the spring on a ledge by a small pond. In early October, migrating flickers regularly come to the island, as well as peregrine falcons who hunt them. John and Terry noted that as soon as a falcon caught a flicker, the ravens approached to try to relieve it of its catch and/or to pick on the remains after the falcon was done feeding. The biologists further saw a refinement of the raven’s use of peregrines: The ravens regularly flushed flickers out of hiding on the ground and the peregrines then caught them. Similarly, John Marzluff reports that in Idaho, ravens immediately appear at half of all rabbit kills that golden eagles make, although whether they also flush hiding prey for the eagles is not known.
If ravens quickly find prey killed by a raptor, might they also find roadkills as quickly? My data are inconclusive. I did take notes in June 1995 on a road trip through raven country between Baker, California, through Las Vegas, Nevada, and on to Salt Lake City, Utah. In all of the 960 miles of road-watching, I never once saw a raven picking at a roadkill. I counted twenty-three roadkills in all. Although most of these were smudges of unidentifiable (at 70 to 80 mph) fur that had been caked onto the highway for days or weeks, I did see four fresh snakes, three jackrabbits, one dog, two skunks, one raccoon, one small bird, and several probable ground squirrels. Not one was attended by ravens. The overall density of roadkills was only one per forty-two miles, and considerably less than that before coming out of the desert and into the green fertile Mormon Valley. Overall, it seemed that the Mojave Desert does not support its many ravens on roadkills.
On a trip in late September of the same year to New York City from Burlington, Vermont, a distance of three hundred miles, I also ticked off every roadkill I saw. I counted the following: three cats, fourteen raccoons, one porcupine, eleven skunks, one bird, one red squirrel, two woodchucks, one hundred and seventy-eight gray squirrels, and ninety-six unidentifiable smears. I had never before seen so many road-killed gray squirrels, and even Newsweek magazine commented on their large numbers that year in the September 5 issue. I saw one hundred and eighty-five big black birds on the highways and in the air. All of those along the highways were American crows, and twenty of those in the air were turkey vultures. As on most trips to Maine, I did not see a single raven on a roadkill, but most roadkills were well attended by crows.
The last week of August 1996, while traveling to Ann Arbor, Michigan, from Vermont through Quebec and Ontario, and back through Ohio, Pennsylvania, and New York, I saw not one run-over squirrel. I did see two road-killed dogs, a skunk, and about two dozen raccoons. I saw two live ravens, one in Ontario and the other in Adirondack Park in New York State, but neither was on a roadkill.
The ravens and roadkill study has a long way to go, but my initial probe could disprove the commonly held hypothesis that the distribution and abundance of ravens is determined by roadkills. It also suggests (but does not prove) that if most raptor-kills immediately attract a raven or two, then it is because they cue in on the hunter itself, not just the dead animal.
Roadkills are undoubtedly an important food supplement for some individual ravens. There are probably some ravens that go on a roadkill cruise daily, as did one or both ravens of the Hills Pond pair by my cabin in Maine. I used to encounter them regularly on my daily jog.
If ravens cue in on the predations of raptors, they must be keen observers indeed. The dozens of other types of large birds that are not raptors would be a waste of time for a raven to watch, and I’m inclined to believe that the ravens’ skill in identifying flying birds of concern to them rivals that of many competent ornithologists. In Baja and Mexico, some ravens even distinguish the zone-tailed hawk, Buteo albonotatus, from the turkey vulture, Cathartes arura. The zone-tail is a black buteo that appears to mimic the turkey vulture in both pl
umage and habit of soaring. Soaring zone-tails tilt their wings in a V, and rock from side to side, as turkey vultures do; and their tails when in flight also mimic vultures’. Gary Clowers, a ravenphile from Oregon who migrates to Baja every winter to watch birds, found these hawks flying frequently with groups of vultures. Most potential prey animals are wary of hawks, but they still ignore the vultures. The hawk appears to use the cover of flying with the vultures to hunt. At first, Gary did not pick out the vulture imposters, but he learned to recognize them only after watching ravens. Near their nests with vulnerable young, ravens rose into the air and attacked the zone-tails, ignoring the vultures.
One pair of ravens impressed me with their ornithological skills while I was on a trip to Umiat, a former center for oil exploration on the Alaskan tundra along the Colville River. One of this pair always perched, guarding their young, on a piece of abandoned machinery. On two different days, I saw the bird suddenly come alive and fly off into the distance making the sharp, short kek-kek predator alarm calls. Straining my eyes, I saw a small black dot in the sky toward which the raven hurried. With my binoculars, I identified the dot as a golden eagle. The raven presumably sought to drive the eagle away, repeatedly diving down onto it. The chase continued, and soon both were out of sight of my ten-power binoculars. I was surprised that the raven not only saw the eagle at least two miles away, but also could distinguish it from such other large birds as Canada and white-fronted geese, sandhill cranes, glaucous gulls, and various ducks and sandpipers, all of which flew by and prompted no reaction.
Of the various ways in which ravens get food, none has received more attention than their presumed attacks on incapacitated large mammals. These sometimes involve grisly scenes. For example, on February 10, 1985, McEneaney in Yellowstone saw a pair of ravens feeding from a bison, taking the only meat they could get, the eyes. The bison was stuck in the mud on the Madison River near Mount Holmes. Its head was lying on the ground, and its only sign of life were clouds of steam coming from its nostrils. No park official would commit the humane act of shooting the suffering beast, because park policy forbids intervention into the affairs of nature. Due to the park’s previous eradication of wolves, thousands of bison and elk had overgrazed the range drastically, altering the whole ecosystem. Now they were starving by the thousands, wandering in search of food and being shot by human hunters. Taking the no-killing policy literally is well-meaning, mindless inflexibility, neither of which ravens can be accused of.
Ravens do perhaps kill dying cattle outside the parks, and that possibility has raised outcries. In the 1980s, two ranchers in northern Arizona reported to the Animal Damage Control Department that ravens were killing their cows, and for several years the Department carried out an ambitious raven eradication program, paying ranchers cash for the cattle they claimed the ravens had killed. Similarly, in Germany there was from 1994 to 1996 a flurry of newspaper articles and television news reports about a gang of fifty or so “killer ravens” that had invaded the idyllic Schwäbische Alb near the town of Balingen. “Nature had turned to horror,” said the press. A shepherd there, Walter Rehm, had described how, “disciplined like soldiers,” the local raven gang would “wait for the signal of the raven boss,” and when he gave “his hoarse signal” they would descend like a regiment and fearlessly attack a victim and “bore into its skull with bills sharp as scalpels” to kill it and pick out its eyes. Of course, all of this was nonsense. There are no disciplined raven gangs, no raven bosses that give descend signals, and certainly no stiletto-sharp raven bills. Raven bills cannot penetrate even the skin of a gray squirrel, much less the skin and skull of a sheep or a calf. Some of my ravens eat roadkill gray squirrel by reaching in through the mouth. By crushing bones and pulling out meat as they feed backward, they eventually turn the squirrel inside out, leaving the skin like an unrolled sock, with not a single hole or tear in it. But only some of my birds could do this neat trick.
Gruesome newspaper tales of bold killer ravens were illustrated with clever pictures of flying ravens splashed across the front pages. The ravens were said to be in “attack flight” with bills wide open—which is a sign of overheating or fright. The television accounts of the raven menace were straight out of a Hitchcock movie. I was sent one gory headline after another. The German Jäger (hunters) soon took up the cry to defend the poor farmers and the poor threatened animals from the new menace. In a letter to the editor in local newspapers, the Jäger offered their invaluable services to maintain the balance of nature, and to end this awful scourge that was, they claimed, also decimating the songbirds, the rabbits, the partridges, and so on.
Preliminary studies revealed that ravens were indeed near or sometimes even in fields where sheep or cattle were giving birth, which was proof enough for those wishing for a cash reimbursement for dead cattle. In northern Germany farmers were, unlike in former times, allowing calving to occur out of doors in the winter, and farmers got cash for dead calves or lambs. Ever more livestock was found in the pastures with their eyes and tongues pecked out, and ravens were as before in attendance. It was an opportunity with something for everyone—the news media, the farmers, the Jäger, the politicians, and even the biologists. When asked to give comments and advice, I said that at least one documentation of a raven killing a cow might be handy. Ravens would feed on afterbirths and on dead or dying lambs. Luckily, our cattle and sheep in New England give birth inside barns, so that ravens cannot be blamed for the innumerable calves that die on their own during birth.
Ravens and other corvid birds have long been persecuted in Germany by the Jäger, a well-organized group that proudly think of themselves as keepers of the natural order. In a disturbed ecosystem that no longer has its natural predators, they do indeed justifiably control deer and boar populations that would otherwise inhibit regeneration of trees, remove underbrush, disturb soil, devastate crops, and affect breeding bird populations. They traditionally also persecute the corvid birds because they are nest predators on other birds. With this latest uproar, the Jäger were clamoring to have the raven taken off the endangered list, so that they could again be shot as in former times, when they were almost totally obliterated from the whole country.
When I visited Germany in 1996, ravens were still getting bad press, and Dieter Wallenschläger, professor of animal ecology and nature conservation at the University of Potsdam, undertook an investigation. We corresponded about the public menace. I personally was dubious of the killer raven stories, because the ravens I was familiar with are cautious even of unattended carcasses. Finding one, they jump up and down in front of it, as if to provoke a reaction. Although I suspect veterinarians have even better means of detecting life, the raven’s method neatly discriminates healthy from just barely alive or dead animals. They would not normally touch a calf that moved, although it is possible that if ravens were to feed often enough on dead or nearly dead calves, they might eventually learn to feed on half-dead ones with less hesitation. Seeing a bird in the act of picking an eye from a dying calf, one might well believe the raven was the cause of the calf’s death.
Dieter heard I was visiting Berlin, and invited me to come to Potsdam. Not only that, he organized a mini-symposium with the title, roughly translated: “Killer Ravens in Brandenburg—Legend or Occupation of a New Ecological Niche?” I was glad to attend. After the introductions, a farmer, Frau Breme, talked of the results of her recent 1996 questionnaire of raven damages that she had sent out to 141 farmers. She got seventy-one returns. Of those, fifty farmers saw ravens, and 41 percent of those saw “Veränderungen” (changes) of animals; i.e., ravens feeding on an animal. In the ensuing discussion of this report, I mentioned the high mortality of calves in New England and the high percentage of Veränderungen of these calves by my ravens, despite absolute proof that these ravens had not killed the calves. German nature conservation people agreed that there was so far not one proven case of a raven causing the death of a healthy calf.
The government had by now
eventually insisted on proof of cause of death before making cash reimbursements. Veterinarians were consulted to make autopsies. Certain examinations of lungs and eyes of newborn calves could determine if the animal had been able to stand when born. Given the examinations, almost all of the calves verändert by ravens had something wrong with them to begin with. They were mostly found to belong to careless farmers who did not take adequate care of their animals. Good farmers didn’t have a raven problem. After the government finally insisted on proof, and after none was forthcoming, the raven damage subsidy became unavailable. Money to study ravens evaporated as well.
The ravens’ dependence on large animals is central to their biology. When we were hunters, ravens were revered companions who inspired poets and engendered creation myths. The presence of ravens meant large animals were near. They meant meat and merriment. All that changed when we became settled herders. Ravens soon became a suspected destroyer of lambs, and prophets of doom and gloom. They were relentlessly persecuted because they were associated with death, although not, as it now seems since scientific study, because they caused it. Ravens’ physical power to kill had been overestimated; and the subtleties of their responses, where their real power lies, underestimated.
An unusual clutch of seven nearly indentically aged young. The different young have small differences in the amount of white on bill. Later the bill will turn totally black.
TWELVE
Adoption
IN MANY SEABIRDS, BATS, AND OTHER colonial species in which parents leave their young among others, there is much opportunity for accidentally feeding others’ young instead of one’s own. These animals have evolved to be capable of identifying their own offspring in a crowd, and they reserve their precious food offerings strictly for them. I wondered how ravens would react to missing or extra young. Could they count? Otto Koehler and his colleagues at Freiburg University in Germany had concluded that they could count to seven, having trained a raven to retrieve food under one of several covered vessels, after training it to expect the food in only one container that had the correct number of spots on the lid.
Mind of the Raven: Investigations and Adventures With Wolf-Birds Page 17
