Raven Today was basically an office day with a bit of optimism about Juliet getting a Den Cam. A conversation with Juliet’s landowner yesterday set us to writing out our case. We hope he agrees.
On a day of simply writing, there has to be some kind of nature distraction. Today, it was a Raven. When we saw it stuffing itself on a big piece of suet, we wondered how much it could carry. It flew off. Shortly, it was back with bits of suet still stuck to its bill. It probably stashed the suet somewhere. It filled up and flew off again. That time, we zipped outside and weighed the remaining suet. When the Raven returned it took only a little (43.5 grams—about an ounce and a half). Not too exciting. Then it came back and did something interesting. It picked up a 209.5-gram piece (nearly a half pound) and flew off. It was too heavy. The flight was labored, and the Raven landed about 75 yards away. There it filled up (70.5 grams) and flew off leaving behind 139 grams (we went and quickly weighed it). Shortly, the Raven returned and easily flew off with the 139-gram piece in its beak.
Gray Jays on deer carcassWhat did we learn? If the Raven weighed 1200 grams as is listed as a typical Raven weight, it had difficulty carrying 17% of its weight (the 209.5 gram piece) but easily carried 12% of its weight (the 139-gram piece). Ravens can’t carry things in their feet, which means they have to carry things in the beak, which is not close to the center of lift when it is flying. Their cousin the Gray Jay can carry food in its feet. That means Gray Jays can place loads close to the center of lift. They can carry about half their weight. Carrying heavier loads helps Gray Jays compete with Ravens for scraps of meat at carcasses.
Gray Jays are cool. Some people think they’re dumb because they come close to people and predators. We think they’re extra smart because coming close shows a willingness to assess risks versus the benefits of stealing food (hence, their nickname Camp-robber). Willingness to assess risks versus benefits is more typical of northern birds like Gray Jays. It’s eat or starve in northern winters. In more productive regions farther south, like in the eastern deciduous forest, food is more abundant. There, predators are the big risk. So, in those areas, avoiding danger is the priority as is shown by the cautious behavior of the Gray Jay’s cousin the Blue Jay.
Back to bear work.
Thank you for all you do.
—Lynn Rogers and Sue Mansfield, Biologists, Wildlife Research Institute and North American Bear Center