Alan C. Kamil

Search Image Formation in the Blue Jay (Cyanocitta cristata)

Blue jays trained to detect Catocala moths in slides were exposed to two types of slide series containing these moths: series of one species and series of two species intermixed. In one-species series, detection ability increased with successive encounters with one prey type. No similar effect occurred in two-species series. These results are a direct demonstration of a specific search image.

Pinyon jays use transitive inference to predict social dominance

Living in large, stable social groups is often considered to favour the evolution of enhanced cognitive abilities, such as recognizing group members, tracking their social status and inferring relationships among them. An individuals place in the social order can be learned through direct interactions with others, but conflicts can be time-consuming and even injurious. Because the number of possible pairwise interactions increases rapidly with group size, members of large social groups will benefit if they can make judgments about relationships on the basis of indirect evidence. Transitive reasoning should therefore be particularly important for social individuals, allowing assessment of relationships from observations of interactions among others. Although a variety of studies have suggested that transitive inference may be used in social settings, the phenomenon has not been demonstrated under controlled conditions in animals. Here we show that highly social pinyon jays (Gymnorhinus cyanocephalus) draw sophisticated inferences about their own dominance status relative to that of strangers that they have observed interacting with known individuals. These results directly demonstrate that animals use transitive inference in social settings and imply that such cognitive capabilities are widespread among social species.

Social complexity and transitive inference in corvids

The social complexity hypothesis asserts that animals living in large social groups should display enhanced cognitive abilities along predictable dimensions. To test this concept, we compared highly social pinyon jays, Gymnorhinus cyanocephalus, with relatively nonsocial western scrub-jays, Aphelocoma californica, on two complex cognitive tasks relevant to the ability to track and assess social relationships. Pinyon jays learned to track multiple dyadic relationships more rapidly and more accurately than scrub-jays and appeared to display a more robust and accurate mechanism of transitive inference. These results provide a clear demonstration of the association between social complexity and cognition in animals.

Visual predators select for crypticity and polymorphism in virtual prey

Cryptically coloured animals commonly occur in several distinct pattern variants. Such phenotypic diversity may be promoted by frequency-dependent predation, in which more abundant variants are attacked disproportionately often, but the hypothesis has never been explicitly tested. Here we report the first controlled experiment on the effects of visual predators on prey crypticity and phenotypic variance, in which blue jays (Cyanocitta cristata) searched for digital moths on computer monitors. Moth phenotypes evolved via a genetic algorithm in which individuals detected by the jays were much less likely to reproduce. Jays often failed to detect atypical cryptic moths, confirming frequency-dependent selection and suggesting the use of searching images, which enhance the detection of common prey. Over successive generations, the moths evolved to become significantly harder to detect, and they showed significantly greater phenotypic variance than non-selected or frequency-independent selected controls.

A comparative study of cache recovery by three corvid species

Abstract The cache recovery behaviour of Clarks nutcrackers, Nucifraga columbiana , pinyon jays, Gymnorhinus cyanocephalus , and scrub jays, Aphelocoma coerulescens , was studied following each of two types of caching sessions. During one caching session, the birds could place about eight caches in any of 15 sand-filled holes available in the floor. During the other caching session, cache site selection was less was tested with 90 holes open. All three species cached and then recovered their caches with accuracies greater than expected by chance. Pinyon jays had a strong tendency to place their caches close together, especially when 90 holes were available for caching. The recovery accuracy of nutcrackers and pinyon jays was higher than that of scrub jays. These results indicate important behavioural differences among these birds that may correlate with differences in natural history. They also suggest that there may be differences in spatial memory ability among these species.

Long-term spatial memory in clark's nutcracker, Nucifraga columbiana

Abstract Clarks nutcrackers, Nucifraga columbiana, are known to depend on cached seeds as their major food source throughout the winter and spring at high elevations; they use spatial memory to locate their hidden seed caches. Field observations of caching in the autumn and recovery in the spring suggest that memory for cache sites may last as long as 7–9 months. Twenty-five Clarks nutcrackers were tested for their ability to remember the location of their caches after intervals of 11, 82, 183 and 285 days. Birds were allowed to make between 18 and 25 discrete caches in a room containing 69 randomly selected sites. After caching, the birds were randomly assigned to one of four retention intervals. Each bird was given three recovery sessions. When the number of caches recovered was compared with the number expected if the birds probed randomly, performance was significantly above chance during each recovery session. There were no significant differences among the groups in percentage of correct probes. There was, however, a significant increase in errors across the three recovery sessions. Birds assigned to the retention interval of 285 days made many more errors during the last recovery session and also took longer to find caches than birds with shorter retention intervals. Although Clarks nutcrackers can remember the locations of cache sites after 285 days, some forgetting appears to occur between 183 and 285 days.

The seed-storing corvid Clark's nutcracker learns geometric relationships among landmarks

Many animals regularly return to particular locations such as hives, nests, wintering grounds or cache sites. This ability clearly implies that animals possess information that allows them to find a route from their current location to their goal. However, the nature of this information is, in many cases, unknown. One particularly important issue is whether this information encodes at least some of the geometric relationships among real-world objects, which would meet a strict definition of a cognitive map. Are animals sensitive to such geometric relationships? Although there is clear evidence that animals can learn vectors that represent a goal location in terms of absolute distance and direction to a landmark, there is little evidence of any ability to extract abstract geometric rules. Here we report data demonstrating that the corvid Clarks nutcracker (Nucifraga columbiana) can learn to find the point halfway between two landmarks that vary in the distance that separates them. This learning is based on a general principle, as the birds correctly find the halfway point when the landmarks are presented with new distances between them. This demonstrates the ability to find a point defined not by the relationship between a goal and a landmark but by the relationship between landmarks. Further experiments demonstrate that there were two distinct processes involved in locating the halfway point, the use of directional bearings to find the (hypothetical) line connecting the landmarks and finding the correct place along that line.

Visual Detection of Cryptic Prey by Blue Jays (Cyanocitta cristata)

Blue jays learned to respond differentially to the presence or absence of Catocala moths in slides. This detection of the moths by the jays was affected by the background upon which the moth was placed and its body orientation, thus providing an objective measure of crypticity. These procedures are useful for the study of visual detection of prey.

Differences in hippocampal volume among food storing corvids.

The hippocampal complex (hippocampus and parahippocampalis) is known to play a role in spatial memory in birds and is known to be larger in food-storing versus non-storing birds. In the present study, we investigated the relative volume of the hippocampal complex in four food-storing corvids: gray-breasted jays (Aphelocoma ultramarina), scrub jays (Aphelocoma coerulescens), pinyon jays (Gymnorhinus cyanocephalus), and Clarks nutcrackers (Nucifraga columbiana). The results show that Clarks nutcrackers have a larger hippocampal complex, relative to both body and total brain size, than the other three species. Clarks nutcrackers rely more extensively on stored food in the wild than the other three species. Clarks nutcrackers also perform better during cache recovery and operant tests of spatial memory than scrub jays. Thus, greater hippocampal volume is associated with better performance in laboratory tests of spatial memory and with stronger dependence on food stores in the wild.

Apostatic selection by blue jays produces balanced polymorphism in virtual prey

Apostatic selection, in which predators overlook rare prey types while consuming an excess of abundant ones, has been assumed to contribute to the maintenance of prey polymorphisms. Such an effect requires predators to respond to changes in the relative abundance of prey, switching to alternatives when a focal prey type becomes less common,. Apostatic selection has often been investigated using fixed relative proportions of prey,, but its effects on predator–prey dynamics have been difficult to demonstrate. Here we report results from a new technique that incorporates computer-generated displays, into an established experimental system, that of blue jays (Cyanocitta cristata) hunting for cryptic Catocala moths. Digital prey images from a virtual population are presented to predators. The relative numbers that escape detection determine the subsequent abundance of each prey type. If apostatic selection does promote stability, the system should converge on an eqlibrium in which each prey type appears at a characteristic abundance. Our results show that the detection of cryptic prey does involve apostatic selection, and that such selection can function to maintain prey polymorphism.