Making Lunch

Here's a sight I see fairly often when I am on the seashore near some rocks. Local seagulls have learned that if they drop tightly closed clam shells onto a rocky outcrop from a height, the shells will break open and the inhabitant can be eaten. Our gulls do this very purposefully and I consider it a kind of tool-using that indicates considerable intelligence.It seems to me something that, though they probably learn it from observing other gulls, perhaps their parents, they must still apply some of their own intelligence to it to get it right. If they drop the clam from too high then lower-flying nearby gulls may swoop down and steal the morsel. If they drop it from too low then it will not crack the shell. Considerable trial and error practice must take place before the technique is perfected and the clam is dropped from high enough to crack the shell but from low enough so that the gull can drop down and eat it before his neighbours do. Seagulls are smart birds.