"DISTANCE EFFECT" IN PIGEON ORIENTATION: AN EVALUATION

¹ Section of Neurobiology and Behavior, Cornell University, Ithaca, New York 14850

1. Matthews (1955, 1963), Schmidt-Koenig (1964, 1966, 1968), and Wallraff (1967) have reported that pigeons orient toward home best when released close to the loft or at a long distance from it; they report poor orientation at intermediate distances, and suggest that this has important implications for the nature of the navigational system used by birds.

2. We have failed to detect any such distance effect in 172 test releases utilizing 2525 single-tossed pigeons from the Cornell lofts. When the homeward component is plotted against distance, we obtain dissimilar curves for the four cardinal directions. Furthermore, the values of the homeward component may be quite different at two release sites approximately the same distance and direction from the loft.

3. We obtained particularly good orientation at the intermediate distances where, according to the distance effect, it should be poorest. This was true not only of experienced birds but also of first-flight youngsters.

4. Analysis of our data, as well as re-analysis of some of the published data of others, indicates that a much clearer picture of the behavior of the birds is given by the combination of the homeward directional component and the length of the mean vector. This permits segregation of the two factors that together determine the homeward component. These two measures vary independently, and neither shows the distance effect.

5. I conclude that the distance effect is not a general phenomenon.