Nucifraga Columbiana Research Articles

A comparative study of geometric rule learning by nutcrackers (Nucifraga columbiana), pigeons (Columba livia) and jackdaws (Corvus monedula).

A comparative study of geometric rule learning by nutcrackers (Nucifraga columbiana), pigeons (Columba livia) and jackdaws (Corvus monedula).

Tests for cognitive mapping in Clark's nutcrackers (Nucifraga columbiana).

In these experiments, the authors examined the nature of the spatial information that Clark's nutcrackers (Nucifraga columbiana) use during navigation and whether this information is represented in the form of a cognitive map. In Experiment 1, nutcrackers were able to use distal cues to locate a small hidden goal. In Experiments 2 and 3, nutcrackers were given the opportunity to develop a map of a room by viewing local subsets of the landmarks in the room at a goal during training. During transfer tests, nutcrackers were presented with a landmark panorama that was not previously seen at the goal. Of 3 nutcrackers that had learned the relationship between distal cues and the goal, 3 were able to locate the goal during transfer, indicating they may have developed a cognitive map. Experiments 4 and 5 suggest that the simpler mechanism of vector integration may have been used by some nutcrackers during the transfer tests.

The Use of Landmarks by Clark's Nutcrackers: First Tests of a New Model

Animals use many different mechanisms to navigate in space. The characteristics of the mechanism employed are usually well-suited to the demands of each particular navigational problem. For example, desert ants navigating in a relatively featureless environment use path integration, birds homing or migrating over long distances use compasses of various sorts, salmon returning to their natal stream home on olfactory cues. The study of navigation requires the study of many different taxa confronting different problems. One interesting case involves scatter-hoarding species that use memory to relocate their hidden food. Such animals face the problem of remembering many locations simultaneously. Clark's nutcrackers (Nucifraga columbiana) are an excellent example, and this paper considers their possible use of multiple bearings from landmarks.

DELAYED SEED GERMINATION IN WHITEBARK PINE AND REGENERATION PATTERNS FOLLOWING THE YELLOWSTONE FIRES

Whitebark pine (Pinus albicaulis) seeds are dispersed by Clark's Nutcracker (Nucifraga columbiana), a bird that makes caches under 2-3 cm of soil. Cached seeds may delay germination for one or more years in part because of underdeveloped embryos at the time of seed dispersal. Consequently, whitebark pine may show a soil seed bank strategy

Search for a hidden goal by clark’s nutcrackers (Nucifraga columbiana) is more accurate inside than outside a landmark array

In three experiments in which an open-room delayed response task was used, we explored how Clark’s nutcrackers use landmarks to search for a hidden goal when multiple potential goal locations were present. In Experiment 1, nutcrackers presented with three spatialsamples were able to use relative local cues from an array that changed positions throughout a session to return to a hidden goal during a test. In Experiment 2, the number of samples varied from one to three prior to the test. The nutcrackers performed as well with one sample as with two or three samples. In Experiment 3, we attempted to increase the cost of searching for the goal but, in contrast to previous reports with nutcrackers, found no improvement in search accuracy. Across all experiments, search accuracy varied reliably for different goal locations, but the pattern of performance at each location was generally consistent. This result suggests that nutcrackers may be using different types of spatial information, depending on goal-landmark relationships. This research was supported by NSF Grant IBN 9421807.

Clark’s Nutcrackers Nucifraga columbiana Remember the Size of Their Cached Seeds

Clark’s nutcrackers (Nucifraga columbiana) hide thousands of seeds in subterranean caches that they later recover using spatial information about cache location. In two experiments, we tested whether nutcrackers also remember another type of information regarding their caches – the size of the seeds in each cache. We videotaped birds during cache recovery and then measured their bill gape during probing behaviour as captured on the videotape. In experiment one, six birds each experienced two treatments: one that allowed them to cache and then recover large seeds, and the other, an identical treatment using small seeds. During this experiment, all six birds used a wider gape when attempting to recover seeds during the large‐seed treatment than during the small‐seed treatment, and gape width was significantly correlated with seed size. During experiment two, we presented birds with both large and small seeds within the same caching session. We also increased the retention interval between caching and recovery. These modifications increased the difficulty of the task. Six of the seven birds used a wider gape during seed recovery when digging for caches that contained large seeds than they did when searching for small seeds. The ability to remember the size of seeds placed within caches may serve to increase the likelihood of speedy and successful recovery. It also allows the birds another level of organization of their food supply. These are the first experiments to suggest that Clark’s nutcrackers remember more about their caches than location alone.

The use of relative and absolute bearings by Clark’s nutcrackers,Nucifraga columbiana

Two groups of Clark’s nutcrackers were trained to find buried seeds whose location was defined by a constant angle from two landmarks whose interlandmark distance and position in the room varied across trials. The first group had a landmark array that was always placed in the same orientation with respect to the walls, allowing the animals to use both relative and absolute bearings. The second group had a landmark array that rotated across trials so that only relative bearings could be used to locate the seeds. The birds in each group learned the task and transferred to new interlandmark distances both within and beyond the range of training distances. Results from these experiments indicate that nutcrackers can learn a geometric relationship that relies exclusively on relative bearings even though the use of absolute bearing yields more efficient search.

Way-Finding and Landmarks: The Multiple-Bearings Hypothesis

Clark's nutcrackers (Nucifraga columbiana) are capable of very precise searching using the metric relationships between a goal and multiple landmarks to relocate the goal location. They can judge the direction more accurately than the distance to a landmark when the landmark is distant from the goal. On the basis of these findings, we propose that nutcrackers use a set of bearings, each a measure of the direction from the goal to a different landmark, when searching for that goal. The results of a simulation demonstrate that increasing the number of landmarks used results in increasingly precise searching. This multiple-bearings hypothesis makes a series of detailed predictions about how the distribution of searches will vary as a function of the geometry of the locations of the relevant landmarks and the goal. It also suggests an explanation for inconsistencies in the literature on the effects of clock-shifts on searching and on homing.

Oportunistic foraging at American Elk, Cervus elaphus, droppings by Clark's Nutcracker, Nucifraga columbiana

Oportunistic foraging at American Elk, Cervus elaphus, droppings by Clark's Nutcracker, Nucifraga columbiana

Geometric rule learning by Clark's nutcrackers (Nucifraga columbiana).

Clark's nutcrackers (Nucifraga columbiana) were trained to search in a location defined by its geometric relationship to 2 landmarks. Two groups were trained to search at different points along the line connecting the landmarks, and 2 groups were trained to find the 3rd point of a triangle, on the basis of either direction or distance from the landmarks. All groups learned and transferred to new interlandmark distances. However, the constant-distance group learned more slowly, searched less accurately, and showed less transfer than the other 3 groups. When tested with new orientations of the landmarks, the birds tended to follow small but not large rotations. When tested with a single landmark, birds in the half, quarter, and constant-bearing groups searched in the appropriate direction from the landmark, but birds in the distance group did not. These results demonstrate that nutcrackers can learn a variety of geometric principles, that directional information may be weighted more heavily than distance information, and that the birds can use both absolute and relative information about spatial relationships.

Geometric rule learning by Clark's nutcrackers (Nucifraga columbiana).

Geometric rule learning by Clark's nutcrackers (Nucifraga columbiana).

The importance of regional dynamics in local populations of limber pine (Pinus flexilis)

Limber pine (Pinus flexilis) populations in the Kananaskis Valley of Alberta have many of the traits of patchy metapopulations based on the reconstruction of the dynamics of 13 local populations. The populations exist in open canopied stands on high stress habitats of rocky ridges, scree slopes, and gravel creek beds. All populations showed continuous recruitment and low mortality. No population showed any evidence of local extinction as a result of negative population growth. Wildfire caused varied responses in the populations from extinction of the local populations to little or no effect. Populations extirpated by fire were quickly recolonized. Seed dispersed by the Clark’s nutcracker (Nucifraga columbiana) appears to be responsible for this rapid recolonization following wildfire. Limber pine does not persist in the seed bank for more than two years. Therefore, the limber pine populations are regionally persistent because rare extinction events (wildfire) are followed by prompt recolonization by seed dispersed by Clark’s nutcracker from other local populations.

Sun compass orientation in seed-caching corvids: its role in spatial memory

The role of sun compass orientation in spatial memory of Clark’s nutcrackers, Nucifraga columbiana, and pinyon jays, Gymnorhinus cyanocephalus, was studied in a series of cache recovery experiments. Birds were tested in an octagonal outdoor aviary with sand-filled cups inserted in the floor. For caching, only 12 such cups in a 90° sector were available, while for recovery 4–7 days later all 48 cups in the entire aviary were open. In control tests, the birds concentrated their search activity in the sector where they had cached. When their internal clock was shifted 6 h between caching and recovery, pinyon jays shifted their search activity to the 90° adjacent sector, as predicted if the sun compass was used. Clark’s nutcrackers did not respond to the first clock-shift; however, they, too, shifted their search activity after a second clock-shift back to normal. This suggests that the sun compass is a component of spatial memory in both species. Clark’s nutcrackers, however, seem to rely on their sun compass to a lesser degree than pinyon jays or the previously studied scrub jays. A comparison of the findings indicates that the role of the sun in spatial memory might reflect differences in habitat and ecology of the three corvid species.

The effect of proximity on landmark use in Clark's nutcrackers

Clark's nutcrackers, Nucifraga columbiana, store thousands of pine seeds during the autumn and retrieve them throughout the winter. It has been shown that these birds are able to use visual cues to relocate hidden food in the laboratory. In this set of experiments, we trained three groups of Clark's nutcrackers to find a hidden food goal that was placed in the same spatial location relative to the testing room. During training, the location of two local cues in relation to the goal differed between the three groups. Group 1 learned the task with the cues closest to the goal, group 2 with the cues further from the goal, and group 3 with the cues furthest from the goal. To test whether the proximity of these two local cues to the goal affected how spatial information was used, we manipulated local and global information in a series of experiments. Results indicated that local cues were more important sources of spatial information for group 1, whereas global cues seemed to be used more by birds in groups 2 and 3. These findings suggest that the proximity of visual cues lead to overshadowing of other sources of spatial information surrounding the goal.

Patterns of movement and orientation during caching and recovery by Clark’s nutcrackers, Nucifraga columbiana

Clark’s nutcrackers regularly store large numbers of pine seeds and remember the locations of the cached seeds. Although they are very accurate, they do make some errors during recovery. In an attempt to determine whether any behaviours during caching predicted the occurrence of errors during recovery, we videotaped Clark’s nutcrackers while they cached and recovered seeds under laboratory conditions. We used the videotapes to develop complete, quantitative descriptions of caching and recovery behaviour, with an emphasis on body orientation and directions of movement. During caching, the birds showed the greatest change in their orientation and direction following cache creation. During cache recovery, in contrast, body orientation changed most following successful recovery of a seed. When orientation while making a cache was compared with orientation when recovering the same cache, orientations were similar more often than would be expected by chance. However, this consistency of direction was not related to the accuracy of cache recovery, indicating that such consistency is not necessary for accurate cache recovery. The location in which the birds chose to place their caches was the only variable that predicted the location of probes during recovery.

FINE-SCALE GENETIC STRUCTURE OF WHITEBARK PINE (PINUS ALBICAULIS): ASSOCIATIONS WITH WATERSHED AND GROWTH FORM.

The fine-scale genetic structure of a subalpine conifer, whitebark pine (Pinus albicaulis Engelm.), was studied at nested geographic levels from watershed to adjacent stems in the eastern Sierra Nevada Range of California. A combination of several characteristics contributed to unpredicted genetic structure in this species. This includes being one of only 20 pine species worldwide with wingless, bird-dispersed seeds; having the reputed capacity to reproduce vegetatively; and forming distinct growth morphologies at different elevations in this part of its natural range. Genetic differentiation, as measured with 21 allozyme loci, among the three studied watersheds is virtually negligible (FST = 0.004). This is a surprising result because the upper-elevation sites vary somewhat in slope aspect; thus, aspect was confounded with watershed effect. Differentiation between the upper-elevation prostrate krummholz thickets and lower-elevation upright tree clump growth forms is modest (FST = 0.051). Much stronger differentiation was measured among the individual thickets and clumps within their sample sites (FST = 0.334). Within krummholz thickets, multiple individuals are present and genetic relationships often resemble half- to full-sibling family structure (mean r = 0.320). Canonical trend surface analysis in two intensively sampled thickets indicates greatest genotypic variation in the direction of the prevailing wind. At lower elevations, most (72%) of the tree clumps contained more than one genotype; the remaining clumps are probably multistemmed trees. Within tree clumps, family relationships are closer than those for krummholz thickets-commonly full-sibling to selfed structure (mean r = 0.597). Genetic structure is apparently profoundly influenced by the seed-caching behavior of Clark's nutcracker (Nucifraga columbiana Wilson). Western pine species typically show little among-population differentiation and high levels of within-population genetic variation. In whitebark pine in the eastern Sierra Nevada of California, genetic variation is highly structured, especially within the natural groupings-krummholz thickets and upright tree clumps.

Sociality and social learning in two species of corvids: the pinyon jay (Gymnorhinus cyanocephalus) and the Clark's nutcracker (Nucifraga columbiana).

The hypothesis that social learning is an adaptive specialization for social living predicts that social species should learn better socially than they do individually, but that nonsocial species should not exhibit a similar enhancement of performance under social learning conditions. The authors compared individual and social learning abilities in 2 corvid species: the highly social pinyon jay (Gymnorhinus cyanocephalus) and the less social Clark's nutcracker (Nucifraga columbiana). The birds were tested on 2 different tasks under individual and social learning conditions. Half learned a motor task individually and a discrimination task socially; the other half learned the motor task socially and the discrimination task individually. Pinyon jays learned faster socially than they did individually, but nutcrackers performed equally well under both learning conditions. Results support the hypothesis that social learning is an adaptive specialization for social living in pinyon jays.

COST OF MUTUALISM: COMPETITION, TREE MORPHOLOGY, AND POLLEN PRODUCTION IN LIMBER PINE CLUSTERS

All aspects of a mutualism may not be optimal for the participating species. We examined possible consequences to limber pine (Pinus flexilis) from competition within reproductive multi-genet tree clusters, which come from multi-seed caches stored by Clark’s Nutcracker (Nucifraga columbiana). Limber pine occurs in three different tree growth forms. We predicted that genets within the tree-cluster growth form would have both reduced radial growth rates and lower pollen-cone whorl production relative to single-trunk and multi-trunk growth forms. We tested these predictions with three populations in the Front Range of the Colorado Rocky Mountains (USA), using ANCOVA models. Genets in clusters had reduced diameters, but similar heights and lower pollen-cone whorl production relative to same-aged genets in the other growth forms. Because seeds stored in clusters represent potential direct fitness loss to parent trees in comparison to seeds stored singly, nutcracker caching behavior may be suboptimal for limber pine at late life-history stages, thus generating a “cost of mutualism.”

Sociality and social learning in two species of corvids: The pinyon jay (Gymnorhinus cyanocephalus) and the Clark's nutcracker (Nucifraga columbiana).

Sociality and social learning in two species of corvids: The pinyon jay (Gymnorhinus cyanocephalus) and the Clark's nutcracker (Nucifraga columbiana).

Use of Landmarks in Three Species of Food‐storing Corvids

AbstractThe use of landmarks by Clark's nutcrackers (Nucifraga columbiana), pinyon jays (Gymnorbinus cyanocepbalus), and Western scrub jays (Apbelocoma coerulescens) was investigated in three experiments. In the first experiment, birds were trained to find a hidden food reward beneath wood chips near a plastic landmark located 20 cm from one edge of a stationary tray. During unrewarded test trials, all species displaced their searching in response to movement of the landmark in both parallel and perpendicular directions; however, searching was displaced significantly more in the parallel direction. In a second experiment, the landmark was removed with the tray stationary or shifted. When the tray was shifted, all species responded by searching relative to the shifted tray. This indicates that the global (room) cues were not being used as salient landmarks. In the third experiment, the tray was placed in different positions for each trial, making global cues unreliable. As in experiment 1, all species displaced their searching in response to parallel and perpendicular movement of the landmark, with movement being similar in both directions. These results indicate no species differences on this landmark‐use task.