Abstract: To test the hypothesis that selection for spatial abilities which require birds to locate and to return accurately to host nests has produced an enlarged hippocampus in brood parasites, three species of cowbird were compared. In shiny cowbirds, females search for host nests without the assistance of the male; in screaming cowbirds, males and females inspect hosts' nests together; in bay-winged cowbirds, neither sex searches because this species is not a brood parasite. As predicted, the two parasitic species had a relatively larger hippocampus than the non-parasitic species. There were no sex differences in relative hippocampus size in screaming or bay-winged cowbirds, but female shiny cowbirds had a larger hippocampus than the male.

Abstract: To understand the animal mind, we have to reconstruct how animals recognize the external world through their own eyes. For the reconstruction to be realistic, explanations must be made both in their proximate causes (brain mechanisms) as well as ultimate causes (evolutionary backgrounds). Here, we review recent advances in the behavioral, psychological, and system-neuroscience studies accomplished using the domestic chick as subjects. Diverse behavioral paradigms are compared (such as filial imprinting, sexual imprinting, one-trial passive avoidance learning, and reinforcement operant conditioning) in their behavioral characterizations (development, sensory and motor aspects of functions, fitness gains) and relevant brain mechanisms. We will stress that common brain regions are shared by these distinct paradigms, particularly those in the ventral telencephalic structures such as AIv (in the archistriatum) and LPO (in the medial striatum). Neuronal ensembles in these regions could code the chick's anticipation for forthcoming events, particularly the quality/quantity and the temporal proximity of rewards. Without the internal representation of the anticipated proximity in LPO, behavioral tolerance will be lost, and the chick makes impulsive choice for a less optimized option. Functional roles of these regions proved compatible with their anatomical counterparts in the mammalian brain, thus suggesting that the neural systems linking between the memorized past and the anticipated future have remained highly conservative through the evolution of the amniotic vertebrates during the last 300 million years. With the conservative nature in mind, research efforts should be oriented toward a unifying theory, which could explain behavioral deviations from optimized foraging, such as “naive curiosity,” “contra-freeloading,” “Concorde fallacy,” and “altruism.”

Abstract: Marsh tits (Parus palustris) store single food items in scattered locations and recover them hours or days later. Some properties of the spatial memory involved were analyzed in two laboratory experiments. In the first, marsh tits were offered 97 sites for storing 12 seeds. They recovered a median of 65% of them 2-3 hr later, making only two errors per seed while doing so. Over trials, they used some sites more often than others, but during recovery they were more likely to visit a site of any preference value if they had stored a seed there that day than if they had not. Recovery performance was much worse if the experimenters moved the seeds between storage and recovery. A fixed search strategy that had some of the same average properties as the tits' search behavior also did worse than the real birds. In Experiment 2, any tendency to visit the same sites on successive daily tests in the aviary was placed in opposition to memory for storage sites by allowing the tits to store more seeds 2 hr after storing a first batch. They tended to avoid individual storage sites holding seeds from the first batch. When the tits searched for all the seeds 2 hr later, they tended to recover more seeds from the second batch than from the first, i.e., there was a recency effect.

Abstract: Several species use the number of young produced as public information (PI) to assess breeding site quality. PI is inaccessible for synchronously breeding birds because nests are empty by the time the young can collect this information. We investigate if location cues are the next best source of inadvertent social information (ISI) used by young prospectors during breeding site choice. We experimentally deployed ISI as decoys and song playbacks of breeding males in suitable and sub-optimal habitats during pre- and post-breeding periods, and monitored territory establishment during the subsequent breeding season for a social, bobolink (Dolichonyx oryzivorus), and a more solitary species, Nelson's sharp-tailed sparrow (Ammodramus nelsoni). The sparrows did not respond to treatments, but bobolinks responded strongly to post-breeding location cues, irrespective of habitat quality. The following year, 17/20 sub-optimal plots to which bobolink males were recruited were defended for at least two weeks, indicating that song heard the previous year could exert a “carry-over attraction” effect on conspecifics the following year. Sixteen recruited males were natal dispersers, as expected when animals have little opportunity to directly sample their natal habitat quality. We suggest that differences in breeding synchronicity may induce an equivalent clinal distribution of ISI use.

Abstract: Darwin argued that between-species differences in intelligence were differences of degree, not of kind. The contemporary ecological approach to animal cognition argues that animals have evolved species-specific and problem-specific processes to solve problems associated with their particular ecological niches: thus different species use different processes, and within a species, different processes are used to tackle problems involving different inputs. This approach contrasts both with Darwin's view and with the general process view, according to which the same central processes of learning and memory are used across an extensive range of problems involving very different inputs. We review evidence relevant to the claim that the learning and memory performance of non-human animals varies according to the nature of the stimuli involved. We first discuss the resource distribution hypothesis, olfactory learning-set formation, and the 'biological constraints' literature, but find no convincing support from these topics for the ecological account of cognition. We then discuss the claim that the performance of birds in spatial tasks of learning and memory is superior in species that depend heavily upon stored food compared to species that either show less dependence upon stored food or do not store food. If it could be shown that storing species enjoy a superiority specifically in spatial (and not non-spatial) tasks, this would argue that spatial tasks are indeed solved using different processes from those used in non-spatial tasks. Our review of this literature does not find a consistent superiority of storing over non-storing birds in spatial tasks, and, in particular, no evidence of enhanced superiority of storing species when the task demands are increased, by, for example, increasing the number of items to be recalled or the duration of the retention period. We discuss also the observation that the hippocampus of storing birds is larger than that of non-storing birds, and find evidence contrary to the view that hippocampal enlargement is associated with enhanced spatial memory; we are, however, unable to suggest a convincing alternative explanation for hippocampal enlargement. The failure to find solid support for the ecological view supports the view that there are no qualitative differences in cognition between animal species in the processes of learning and memory. We also argue that our review supports our contention that speculation about the phylogenetic development and function of behavioural processes does not provide a solid basis for gaining insight into the nature of those processes. We end by confessing to a belief in one major qualitative difference in cognition in animals: we believe that humans alone are capable of acquiring language, and that it is this capacity that divides our intelligence so sharply from non-human intelligence.