igoddard's Journal

In addition to enjoying wind surfing, this clever raven is recruiting the force of strong upslope wind to facilitate easier eating of foot-held ice. If it sat on a branch, it could not easily grasp both the branch and this large flat chunk of ice. If the raven pecked at this piece of ice on the cliff rocks where it was found, it would slide away. If the raven was in normal flight without powerful winds holding it aloft, flapping its wings instead, it would be more cumbersome to eat and the raven would carry its full weight. The powerful wind held aloft both the raven and the ice for free, allowing the raven to nibble on the ice held in its feet as casually as you would nibble on an ice-cream cone in your hand. See this full observation in my video showing the raven eating the ice.

Is this similar to tool use?

If this raven was intentionally recruiting wind to facilitate eating ice, as it seems to be, imo, then it seems as if it was using the wind as a tool. Let's express this utilitarian hypothesis as a formula and apply it to a famous example of tool use by crows and then to this scenario.

• W uses X to facilitate manipulation of Y so as to achieve Z.

• A crow uses a stick to facilitate manipulation of grubs so as to achieve food.

• A raven uses wind to facilitate manipulation of ice so as to achieve food/drink.

An important difference is that, while a stick is an object manipulated as a tool, the wind is not an object. However, the raven nevertheless manipulates the wind aerodynamically in just the right way to hold it aloft thereby facilitating easy eating of the ice. Both sticks and winds are physical phenomena that are being recruited in these examples as a means to an end, so the object distinction seems rather arbitrary. However imperfectly the proposed intentional use of wind may conform to the formal concept of tool use, it seems to require similar levels of cognitive insight, which ravens and crows are known to possess.

In early September I observed two ravens performing a series of synchronized aerobatics, possibly expressing courtship or pair-bonding behavior. The two ravens repeatedly dove in unison and turned to face each other during their mirrored downward trajectories, even when doing so required rolling over to briefly fly upside down so as to face the other. They also often extended their feet toward the other as they faced each other, possibly making foot-to-foot contact sometimes. During the full video of the observation, we can see them dive in unison seventeen times in a row with brief periods of normal flight between dives.

During each dive I could hear them call, "auck auck auck." While the camera's microphone failed to pick up those calls, you can see the beak of one or both opening as they fall and call. Even when the local ravens I observe dive alone, they usually do the same three aucks, which I have captured in some videos. So calling while falling appears to be a rule among those ravens. But is it universal raven trait? Given ravens are so intelligent, perhaps unique customs develop in different regions.

This video of the observation is stabilized and fitted into tall format from the original video, significantly improving the visibility of subtle behavioral details obscured in the original due to handheld shakiness. But it's still worth seeing the original too because it shows more context and allows the bird's falling during dives to be better seen versus always being centered in the frame, as above. In a stabilized video, the edges of the original video can intrude into the frame, appearing like a black panel sweeping in from an edge, which is very distracting. So, where that happens I've replaced the black with a sky-matching color, which causes the birds to appear to vanish for a few instants exactly where they went out of frame in the original.

Similar observations

Searching Google Scholar, I have not found any papers mentioning synchronized raven aerobatics like we see above. If you know of any references in the literature, please post them in comments below. Searching more broadly, I found some videos that captured similar behavior. In Example 1 (the original source of which I have not found) and Example 2, we see several in-unison dives between two ravens, albeit without the face-to-face rotations seen above. Examples 1 and 2 appear to demonstrate the same behavior seen above. In Example 3 we have reported aerobatic courtship behavior with foot grasping, but, overall, not as synchronized. In Example 4 and Example 5, we see single face-to-face dives between two ravens, but there's no indication that it continued in a series of synchronized dives and in 5 the videographer says the birds were dueling. In contrast, the behavior of the ravens above and in Examples 1 and 2 appears to be consistent with mutually desired pair bonding.