Discrimination and generalization of leaf damage by blue jays (Cyanocitta cristata)

Abstract

Blue jays (Cyanocitta cristata) responded to projected black-and-white silhouettes of cherry leaves that were either undamaged or were damaged by either cryptic caterpillars that disguise leaf damage due to their feeding or by noncryptic caterpillars that do not disguise leaf damage due to their feeding. Pecks to the key on which the images were projected were reinforced only if interresponse times fell within specified temporal boundaries. These boundaries were different in the presence of the two types of leaf damage. Following training with one exemplar of each damage type, the jays correctly categorized novel instances of both types. They categorized novel undamaged leaves as if they were examples of leaves showing damage by cryptic caterpillars. Results suggest that the jays can readily discriminate and generalize to new members of a polymorphous stimulus class. The results suggest that techniques for the study of concept formation in animals can be applied to an animal's ability to categorize stimuli that are involved in a potential prey-predator relationship.Many palatable, highly cryptic, leaf-eating caterpillars have feeding behaviors that appear to disguise or eliminate evidence of leaf damage due to feeding. These caterpillars pare leaves evenly, often snipping off the leaves on which they have fed. Unpalatable, noncryptic caterpillars lack these behaviors. These caterpillars leave abundant evidence of their feeding. The leaves on which unpalatable caterpillars have fed are often left in tatters (Heinrich, 1979). Heinrich and Collins (1983) have suggested that the feeding stategies of the cryptic caterpillars may have evolved under predation pressures to further reduce their visibility, and they have demonstrated that black-capped chickadees (Parus atricapillus) can use both artificial and naturally occurring leaf damage as a means of localizing prey items. Their data indicate that birds are capable of discriminating leaf damage and that leaf damage may determine the locus of foraging efforts. Their data suggest, more indirectly, that foraging behaviors may be determined, at least in part, by leaf or leaf-damage characteristics as a result of

Selective Attention, Priming, and Foraging Behavior

“…In other words, the birds showed hunting by expectation, appearing to form an association between particular areas and particular reward rates. Other studies have reported similar findings from a variety of settings, including patch selection and responses to leaf damage in insectivorous birds (Heinrich & Collins, 1983;Kono, Reid, & Kamil, 1998;Real, Ianazzi, Kamil, & Heinrich, 1984;Smith & Dawkins, 1971;Smith & Sweatmen, 1974). Pulliam (1991, 1993) conducted a detailed aviary study of the foraging behavior of white-throated sparrows on small cryptic or conspicuous seeds and found clear indications that the birds selected habitat patches based on their expected detection rates, with diet composition changing accordingly.…”

Visual search and attention in blue jays (Cyanocitta cristata): Associative cuing and sequential priming.

“…Croze surmised that features of the familiar foraging area associatively cued a search for red targets, a process analogous to contextual cuing in human subjects (Chun, 2000). Similar findings have been reported from the responses of insectivorous birds to visual indications of leaf damage (Heinrich & Collins, 1983; Real, Ianazzi, Kamil, & Heinrich, 1984). …”

Learning specificity in acquired predator recognition

“…Although recognition of natural objects has been explored in several systems (e.g. Curio 1993;Jedrzewski et al 1993;Evans & Marler 1995), much less is known about how animals categorize complex stimuli about which they have learnt (although see Kramer & von St Paul 1951;Herrnstein et al 1976;Herrnstein 1979;Real et al 1984).…”