The timer chip was crucial because it prevented the camera from switching on too soon and running out of battery power before capturing meaningful behavior. "When you first release a bird, the first thing it will do is sort out its feathers," Rutz says. "We didn't want to film this because we only had about 70 minutes worth of battery life." In fact, the average length of the footage recorded by each of the cameras was 38 minutes.
The researchers rounded up 18 crows in about a week using a baited five- by three-meter (roughly 16- by nine-foot) net placed on the ground. They ended up getting footage from 12 of those birds.
The researchers relied on the VHF radio-tags to find the cameras after the birds shed them but wound up recovering fewer than half because each tag's signal lasted only about three weeks. Rutz says he and his colleagues did not have to retrieve the cameras to recover their data (although each unit was worth several thousand dollars), because the video feeds were broadcast to a receiver that fed the footage into a camcorder.
The crows filmed themselves using tools to search for grubs in the rotted wood of fallen trees and to fish for ants in the ground. Researchers were surprised to discover that they used dry grass stems in addition to sticks and leaf stems. "We now know we were getting only a fraction of the whole picture," Rutz says. "This cautions us to broaden our view."
Rutz and his team are considering strapping cameras onto dozens of other crows in an effort to create a comprehensive video catalogue that will help them understand, among other things, whether females or males use tools more. "Does each crow have its own tool kit or are there crows that serve as tool specialists for the group?" Rutz asks. "These are important questions."
Rutz plans to rejoin colleague Lucas Bluff in New Caledonia within the next week to continue their studies. They have already begun to work on improving the camera units and are hoping that their "crowcam" technology can be used to study other types of birds and animals in the wild. "I'd like to see video tracking become routine for field ornithologists, or biologists in general," he says.