Mind of the Raven: Investigations and Adventures With Wolf-Birds (13 page)

Previous data from amateur ornithologists who had tracked the location of raven nests since their recovery in northern Germany in the 1960s showed that the nests were already dispersed, even when there were many fewer birds, well before the present nest density of 2.3 pairs per 100 square kilometers was achieved. Absolute size of territory had changed, but the tendency for nests to be located away from neighbors was preserved. This meant that territory size of ravens is not a given. Ravens do not exclude others at a set distance from the nest. Barring a sampling problem, territory size seemed to have changed through time. Territories were large at first, then in later years they apparently had shrunk. Surely, the ravens hadn’t changed. Their reactions to each other had.

Another pattern in the black dots on the map was that very few new ones had appeared in recent years. Each nest was still producing three to five young each spring, more than doubling the whole population of these very long-lived birds every single year. Why did the number of breeders stay constant? Johannes Goethe, working in the Mecklenburg area of northeastern Germany, and Derek Ratcliffe in Britain had found the same patterns of dispersed nest spacing, with at first a steady increase and then a limit or ceiling in the number of breeding pairs. What was happening to all the birds? They seemed to vanish.

Only isolated individuals of the 1,860 nestlings that Thomas and Volker had so far banded found breeding territories within his study area. Thomas had documented five individuals that settled down to breed, but only at ages seven, five, four, four, and four years, even though ravens can breed at the age of three years. These results showed that breeding in ravens is a privilege of the select few, and that privilege is not easily acquired.

Derek Ratcliffe had drawn data from the efforts of hundreds of eager cliff climbers and amateur British ornithologists who had for decades ascended to the nests of ravens. He had at his disposal an impressive data set on the population ecology of ravens in Britain.
These data allowed him to assess how raven territoriality related to different land uses, the available food supply, and to raven persecution past and present. Ratcliffe determined that the key to nest spacing is primarily food supply. Where food is scarce, territories are large, and where there is much food, along seacoasts and in areas of intensive sheep pasturage, territories become smaller. In the Shetland Islands, for example, twelve active nests were found within 5 kilometers of a large garbage dump (Ewins, Dymond, and Marquiss, 1986). Ratcliffe concluded that under conditions of copious food supply, ravens become extremely tolerant of the close proximity of neighbors, and territoriality virtually breaks down.

Many corvids are mutually attracted to one another, and clumped nest spacing and even dense colonies is typical in species such as rooks, jackdaws, and pinion jays. Ravens are almost unique among corvids, and more like raptors in their generally wide nest dispersal and strong territoriality. With many birds, territoriality is considered the result of an inflexible and innate antagonism to neighbors that
functions
in monopolizing an adequate food supply, but is not directly related to it, so that territory size remains constant despite food supply. Is the raven different? Is the raven’s intolerance a function of its stomach contents? We don’t know. We’ve seen the result—the black dots on the map, but we’ve seldom seen the dramas that transpire to achieve the specific nest spacings.

I suspect that neither Grünkorn’s nor Ratcliffe’s results can be explained by one cause alone. Low food supply probably reduces the level of tolerance and causes nest dispersion, while increasing time of residency (as neighbors get to know one another) may increase tolerance, instead tending to reduce nest dispersion.

We know that the ravens’ adult occupancy in their territory is not all-or-nothing. For several years, I have seen a pair spend weeks near a cliff less than a mile from my house in Vermont. They roost there at night, and in the spring start to bring sticks for a nest foundation, then leave for a month or more. Goliath and his eventual mate Whitefeather, a wild raven, who was a sometime resident of my aviary, were absent from their territory for a two-week stretch after breeding in the
summer of 1996, and for months during the following years. After finding a mate, ravens apparently try to settle down, but whether they are successful in becoming permanent residents and consistently raising young is another matter. It may take a long time to get established, and even once a site is chosen, the birds do not necessarily stay there all the time. “Vagrant” and “resident” are not absolute categories. Individual differences, or the birds’ finely attuned responses to conditions, could determine just how resident or vagrant they are.

I
N THE LITERATURE OF RAVENS AS
well as in common usage, a group of ravens feeding together is almost invariably referred to as a “flock.” Unfortunately, this is an assumption. A flock is a group that has a membership. The term “flock” could apply to a group of geese, starlings, crows, or ravens that flies together toward a common destination or that stays together for some other common purpose. Many birds stay in cohesive flocks for long portions of their lives, feeding together, flying together, and sleeping together. Their behavior contrasts hugely from that of others who may be found in equally large numbers at a certain time in a certain place. For example, hundreds of ravens could be at a carcass because that is the only one around. Do all the individuals come and go independently? After watching marked individual
ravens at baits in crowds I have the impression that they are no more flock members than diners in a city restaurant are necessarily members of a cohesive group. Nevertheless, raven individuals might possibly maintain a group membership in some way that was invisible to me. There was only one way to find out: track them.

I had a second reason for wanting to track ravens from one feeding crowd. Early in my raven studies, I noted that many birds in a feeding crowd would remove great quantities of meat from a carcass to hide it at a distance in the snow, as if for later use. Yet, as soon as a carcass was stripped of meat, all the birds seemed to vanish. Did they leave the area because their memory was so poor that they could not remember where they had hidden their stash? Did they stay to feed on hidden caches, but remain hidden so that I missed them? Tracking several birds from a feeding crowd would help answer these questions as well.

Kristin Schaumburg, a student at Sterling College, had come to me earlier in the winter wanting to work on ravens for college credit, since each student at the college was required to do a project “in the field.” She was willing to work for free, she had a car, and the thought of radio-tracking ravens appealed to her.

Delia Kaye and Ted Knight, two former University of Vermont students, were also interested in the outdoors and wanted to take a break from making a living. That was enough person-power to do a project. I had secured time off by doubling my teaching duties for a semester, and so our merry crew of four gathered at the cabin. Our plan was to capture and radio-tag ten ravens from one feeding crowd on a carcass. The birds would then be released back into the remainder of the feeding group at the same carcass. About two days later, we would remove the food. Might all the birds then soar off together and stay together as a group?

First, we had to capture the ravens. The event was scheduled for Sunday morning, January 6. All day January 5, we worked to get ready for the big raven roundup. Wolfe Wagman, another friend and former University of Vermont student, worked with us to fix holes in the big chicken-wire raven trap. I tested the door of the trap by pulling the wire from the newly renovated and camouflaged spruce blind nearby. In the previous weeks, I had already lured a big group of
ravens to feed inside the open trap. Four carcasses still remained inside to be eaten, and we added some fresh pork lung for a final irresistible inducement. We were ready! We finished the preparations as it was just getting dark, and went back to the cabin. Ten more student reinforcements came that evening from the University of Vermont to join us. All were ready for a big capture.

The alarm clock rudely clanged next to my ear at 6
A.M.
in the darkness. A heavy rain pummeled the roof, but there was nothing else to do except hang tough. Four of us rolled out of our beds, stumbled down the trail, and dove into the dark spruce blind. There, lying on our backs, we felt the drops of ice-cold, snow-filtered water dripping off the soaked fir boughs—
splat, splat, splat
—onto our faces. We lasted for two hours.

Only two birds showed. One perched for a while directly over us, giving voice to a repertoire of sounds that reminded me of gurgling-dripping water. Later, another flew over. Its wing-beats were irregular, not the usual slow, steady, businesslike
swish, swish, swish
. What had happened to the crowd? The raven crowds’ sudden absence continued for the next week, the week after that, and still two more weeks.

Ravens again came into the trap on February 4 after a fresh snowstorm. In preparation for another roundup attempt, we built a large fire under the stars, slapped big steaks stuffed with garlic onto the grill, and put our arms around each other. The snow had come! Everything was right. This time we would catch all the ravens we wanted, and all we needed was ten. We would then get answers to our questions.

The capture was not successful until February 10, 1992. We caught ten birds, and using Superglue and dental floss, attached a radio to the tail-feathers of each one. We released them at the bait close to the capture site where a large crowd had continued to feed. We then removed the bait, and soon had results from the radio-tracking coming in. No birds were hanging about in the woods near the bait. Nor did they gather up to leave all together as a group. Two birds apparently left the county immediately. As we found over the next three months, none of the ten were regularly sleeping or foraging together. They dispersed all over the place.

We worked in shifts. One of us drove at night, taking radio bearings trying to detect birds at sleeping roosts. Another drove daily along one of three fifty- to sixty-mile road loops, stopping about every two miles to see if we could get any radio signals. Usually, we got none. It was tedious work. To find any birds, we had to enlarge our search far beyond the local area. We were searching over a 1,500-square-mile area, driving more than a hundred miles per day.

One night around 9:00
P.M.
, Ted came back with word that he’d again got a radio fix on Number 9680 roosting down near the lake. She was not sleeping with any of our other marked birds. It was a beautiful cold clear night, with the moon glow making the snow a milky bluish white—a good night to take a hike to find out if she was with the others or alone. Snow crystals crunched underfoot as we descended the trail from the cabin. We soon entered a thick, dark spruce bog where the wires from the earphones and the rods of the antenna kept snagging on branches. We lost our sense of direction, but whenever we put on the earphones, we could reconnect using the loud metronomic
click, click, click
of the birds’ radio. We went ever onward into the swamp, toward a dense stand of white pine trees. We approached the likely spot cautiously, stopped, looked up, and suddenly heard a wild clatter of powerful wing-beats crashing through the branches. More than twenty huge black shapes scattered in all directions, vanishing into the night. We had our answer: Number 9680 did not sleep alone, even though she was not with any of the ten other ravens with which she had been feeding when we caught her.

The next day, February 11, Kristin, who tracked over toward Augusta, got no signals all the way there; but while coming through the Belgrade Lakes region on the way back, she got Number 9680 again—the very same bird we had traced near Webb Lake the previous night. Before breakfast that morning, 9680 had also circled over us at a bait that we inspected some thirty miles from where Kristin later found her. She had traveled all that distance, despite the plentiful food that was locally available. Number 8510 was also near Belgrade along with 9680, then he flew on to the Dryden dump, where Number 8300 had been all day.

It was my turn for the night run that evening. It was snowing when I started out in my four-wheel drive. The snow was falling so thickly that my headlights shone up against an almost solid wall of white. I could just barely make out the white lines—the snowbanks on each side—with my peripheral vision. I tried to take readings from all the high elevations, which meant driving on narrow logging roads at times. They all had solid walls of dark forest on both sides, but they were well plowed to allow for the passage of trucks in the daytime.

My first contact was with bird Number 8510, at McGrath Hill Road near Wilton. We had routinely found this bird at this spot at night. Some birds had roosted in one location only for two or three days, then were gone. This bird came back to the same spot each night for weeks. As we would later discover, it had taken a mate, and it stayed in the area at least until spring but did not nest there. It slept there only with its mate. Going on to East Dixfield and past Carthage, I found nothing. At one spot along the lake near Weld, I picked up a weak signal from Number 9239 that I later localized to Center Hill: I’d located my second bird, and my loop of fifty-nine miles was nearly complete. It had been a good night. I had collected two data points to plug into the graphs, ultimately showing these birds were apparently not organized into groups, at this time, under these conditions.

Two years later, in 1994, I organized the next obvious project with Ted, Delia, and a new recruit, Eileen Connor. We would tackle the challenge of studying the “territorial” residents. I had again taken on a double teaching load the fall semester in order to have the winter semester off for this project. As before, the first priority was to catch the birds—this time the territorial adults. We could not use our walk-in trap because by now the territorial birds were all wise to it. We had to capture individual birds that I knew. The rub was that they probably knew me.

The walk-in trap being useless, we had to use leg-hold traps, a task I didn’t relish. From a local trapper, I got a large selection of them. I judged a Number 1 would be small enough not to injure a raven’s leg, but to be safe I hacksawed off one of the two springs, halving the power. I weakened the remaining spring by heating the trap in
the woodstove among red-hot coals. We then duct-taped pipe insulation around each of the two jaws of the trap. When the trap was not in use, the jaws were held slightly open with a laundry pin to prevent the insulation from gradually depressing and losing its cushioning effect. I tested one of our altered traps by snapping it shut onto my fingers. It caused no undue damage. I hoped the traps would still be strong enough to hold a raven by a leg or foot.

Setting a trap presumes you know how to depress the spring. As you bend the jaws over to engage the trigger on the pan, you’ve got to bend the metal tag holding the trigger just right so that the added pipe insulation that you’ve got to press down does not cause too much tension on the trigger. You’ve got to be able to set it so that a light tread will trip it. Setting your trap this way in the cabin is one thing. Out in the field, it’s quite something else. It has to be set in the snow. In the field, the sun causes melt in the day, which then freezes at night. Once ice gets on the trap, it becomes inoperative, so when a trap is set in open snow, as ours would be, the metal had to be kept free of snow. There can be nothing under the pan, a place where snow could lodge easily. To mitigate against that happening, I put wax paper over the pan in a shape that just fit in the opened jaws. I tried to keep the wax paper dry by sprinkling barley chaff over it and the trap. I then sprinkled snow to hide the dry chaff. The chain attaching the trap to a small tree was also hidden under the snow. Setting the trap was still the easiest part. The next step for ensuring trapping success was knowing where to put down the set.

During the previous ten years, we had found seven adjacent nests of ravens. This was an ideal situation, because we could now distinguish, at least in theory, if the birds defended a large territory or only their nest site itself. If the latter was true, then several pairs might show up at a single large food bonanza like a large cow carcass. But providing a large bait could attract hundreds of birds and was not the way to go. We’d catch mostly vagrants, and vagrants in a trap at any one site would tip off residents to stay clear of that site. To increase the chances of catching only territorial birds, we had to discourage vagrants. The best solution might be to use very small baits, and place
them with a trap very close to nest sites. Therefore, we had provided no baits all winter long, so that few vagrants would be in the vicinity when we started trying to trap residents.

I set out baits one weekend in late February, just before the nesting season began, when both members of the resident pair should be near the nest site. The female, who after the eggs are laid is fed entirely by the male, might still be captured because she would still be feeding herself. I hoped to get both members of each pair gradually used to feeding at one spot, then set the trap there. But first I had to find an irresistible bait. I had located a dead horse at a local farm and provided chunks of horse meat half-buried in the snow. Then I added peanuts, bits of leftover pancake, and corn chips.

After the first week, there had been raven tracks at only four of the dozen baits I put out. I learned that details matter. At one bait, a raven had fed on a piece of meat sticking out of the snow. I then strewed a handful of peanuts all around. Two days later, there were again raven tracks all around—but the raven no longer went to the meat it had fed on previously. The tracks showed that the bird had paced about a good deal, and it had taken all but two of the peanuts—and the two it had left were those that I had placed onto the meat that it had fed from previously! I obliterated the raven’s tracks every day, to see where new tracks might be put down, to determine what the bird might be up to next.

On March 2, six days into the raven-catching project, it was still not yet time to set the first trap. Increasingly, I’d started to consider my study of the ravens to be a miniature military campaign. I was the general, plotting strategy. The ravens were the wily foe. The situation resembled what the Chinese philosopher Lao-tzu in the text of Tao Te Ching described more than 2,500 years ago. He said that the best athlete wants his opponent at his best, and the best general enters the mind of his enemy.