companions. (Similarly, in food luring, domestic cockerels have been shown to tailor their vocal signals both to the nature of the food referent and to that of the conspecific receiver ( Marler, Dufty, & Pickert, 1986a, 1986b). In this case egoistic benefits cannot suffice to bring about the full response. Thus the door is open to cheating, e.g., withholding vital information, if no benefit is expected from passing it on. A qualitative species difference, such as this one, seems to transcend mere species differences in the "salience of stimuli" and the "motivation" of the subjects involved ( Shettleworth, 1984) and, thus, appears to mirror a genuine constraint of the learning mechanism, i.e., on the behavior of both the potential tutor and the potential learner.
My sincere thanks go to all who were involved in the experimental work: H.-W. Böcking, U. Ernst, E. Frankenberg, W. Hoffmann, E. Kretzschmar, C. Lombardi, B. Stevens, and W. Vieth. W. Windt critically read the manuscript. I also gratefully acknowledge the stimulating discussions in the Tuesday colloquium of the Arbeitsgruppe. Dr. W. Scherzinger generously donated the Brazilian pygmy owl. The Deutsche Forschungsgemeinschaft supported the work over many years by various grants.
Curio E. ( 1969). Funktionswelse und Stammesgeschichte des Flugfeinderkennens einiger Darwinfinken (Geospizinae). Zeitschrift für Tierpsychologie, 26, 394-487.
Curio E. ( 1971). "Die akustische Wirkung von Feindalarmen auf einige Singvögel". Journal für Ornithologie, 112, 365-372.
Curio E., Ernst U., & Vieth W. ( 1978). The adaptive significance of avian mobbing. II. Cultural transmission of enemy recognition in blackbirds: Effectiveness and some constraints. Zeitschrift für Tierpsychologie, 48, 184-202.
Diamond J. M. ( 1985). Rats as agents of extermination. Nature, 318, 602-603.
Fleuster W. ( 1973). "Versuche zur Reaktion freilebender Vögel auf Klangattrappen verschiedener Buchfinkenalarme". Journal für Ornithologie, 114, 417-428.
Frankenberg E. ( 1981). The adaptive significance of avian mobbing. IV. "Alerting