On a winter day in 1984, Bernd Heinrich followed the calls of a group of ravens near his cabin in the Maine woods. The birds led him to a moose that had been killed by a poacher. “The ravens showed me where it was,” he said.

“I figured if I could understand what they were talking about, a total neophyte, they could certainly tell each other.” He set out to learn if there was a particular raven call associated with food, and if the birds used that call to recruit other ravens.

“I figured I’d get that done in a week or so,” he recalled, “and that’d solve the problem.”

Twenty years have passed, and Heinrich is still finding new mysteries to solve in the minds of ravens. Recently he captivated listeners at Bingham Auditorium in Bethel with the story of his “journey to find out.”

Heinrich observed a sheep carcass he had left in the snow for four days. On the first two days, single birds flew by, but none landed to eat. On day three, a group of 20 birds arrived all at once to feed on the sheep. On the fourth day, 40 birds came to the carcass, so many that they had to take turns eating.

Heinrich noted that once food has been discovered, the birds arrived as a group, which implies that one raven finds the food and then brings the others. But the question remained “how could they tell the other birds?”

“Juveniles who don’t have a territory gather together to roost,” Heinrich said. His observations of raven roosts showed that although the birds come to the roost from different directions, they all leave together, in the same direction and at the same time. “How they do it, we don’t know,” he said.

The mystery of raven communication remains unsolved.

Another mystery, however, was uncovered. Why, Heinrich wondered, would the birds share food with others when they could have it all to themselves? His first hypothesis was that the groups of ravens who fed together were related. The birds’ DNA showed that they were not.

Heinrich’s second hypothesis was that, once formed, groups of birds always stay together. He attached radio tags to ravens feeding at a carcass he had left out for them. Tracking the signals, he found that “they didn’t sleep together and they didn’t fly together.” The birds were not bound by any obligation to each other.

Heinrich found his answer by looking at the ages of the group members. Where most groups of birds are comprised mostly of adults, the raven groups had very few adults.

There was also a lot of fighting among the feeding birds, and the “chasers” were usually the adults.

Heinrich realized that the adults among the group were trying to defend their food so they could feed their young. The only hope juvenile birds, who have left their nests but not yet found a mate, had of eating was to form a group large enough to stand up to the territorial adults. The question of why, if not how, the groups were formed had been answered.

Frank Vogt, a member of the Mahoosuc Land Trust, which hosted the talk, and longtime friend of Heinrich, told audience members to look for a new book by Heinrich in a few months about the Canadian geese that live in a bog near his home.