top ten: gull (non-menacing)

(Click for larger image, showing very cool eye)

We resume our photo parade through San Francisco with the gull, as promised.

In addition to not assaulting me, this nice gull is also giving us a perfect view of the brilliant red spot on its lower bill. We know that this spot is used by hungry chicklets, who tap it with their own beaks to beg for food. But behind the habit lie interesting details about the nature, or nurture, of animal instinct.

The laughing gull (Leucophaeus atricilla) was the star of Niko Tinbergen’s studies of sign stimulus and food regurgitation response, later expanded by Jack Hailman in his intriguingly titled Scientific American article “How an instinct is learned”. Returning to the nest, an adult laughing gull swings its head from side to side. Peck the red spot and the chick receives food. Tinbergen’s experiments using model birds revealed that, if the red spot were anywhere else on the head, the young gulls would fail to peck. Ignore it completely. They’d tap to elicit food only when the spot was in the right, er, spot.

But the swinging action of the bill, too, has its role to play. In their first feedings, baby gulls would often miss the moving target. With practice, their accuracy increased until they reliably pecked the red spot in motion.

It’s a complex interaction: the stimulus of a precisely placed spot instinctively evokes pecking, and the swinging motion promotes learning of visual and muscular skills. Through observations like these, ethologists came to understand “instinct” not as inborn, unminded and ancient response, but as a behavior pattern pre-programmed to develop.

(And if you think this is fascinating, wait until we uncover Tinbergen’s juicy revelations about the life of the three-spined stickleback. Ooh, as they say, la la.)