Perisoreus Canadensis Research Articles

Food Storage in Gray Jays: Source Type and Cache Dispersion

AbstractAnimals that store food items in scattered sites must decide how to distribute their caches in space. Our theoretical approach is based on the assumption that such animals disperse their caches in a manner that maximizes the long‐term rate of storage of recoverable (surviving) food items in the habitat. We investigate the cache‐spacing behavior of theoretical scatter hoarders that encounter food sources differing in the energetic content of the items they contain. We then describe a field experiment in which gray jays (Perisoreus canadensis) were presented with both small‐ and large‐item food sources. The jays compensated for source type by spacing larger‐item caches more widely, a compensation that would tend to yield a high rate of storage of recoverable food energy over the long term and throughout the territory. Previous models do not adequately account for the observed patterns of cache dispersion.

Social Hoarding and a Load Size-Distance Relationship in Gray Jays

A model that assumes scatterhoarders maximize the rate at which they store food that survives densitydependent theft by competitors has been developed elsewhere (Waite 1991a; Waite and Reeve 1992a, 1992b). The model addresses the questions of how such hoarders should distribute caches of food items collected from an ephemeral, locally abundant source, and how long they should persist in caching from such a source before moving on in search of alternative sources. The results of several field experiments using Gray Jays (Perisoreus canadensis) were qualitatively consistent with the model in most contexts (references above). However, because the model implicitly assumes that a hoarder's behavior is not influenced by that of other individuals, methodological measures were taken in those experiments to eliminate any confounding effects of social context on the jays' caching behavior. Here, I describe a simple field experiment designed to investigate whether the distance to which Gray Jays transport food items for storage is affected by load (food-item) size and social context (solitary or in the company of one or more conspecifics). I present evidence that apparent attempts by the jays to cache secretively were influenced by the size (value) of the food item, the immediate risk of losing a cache to a conspecific soon after the cache had been put in place, and the interaction of these two factors (food-item size and social context). Any tendency to cache secretively may reduce the probability of cache theft, which may be accomplished also by adequately spacing caches (Waite 1988, Waite and Reeve 1992a), appropriately timing the decision to move on to alternative sources while a known source still contains food (Waite and Reeve 1992b), placing caches in inconspicuous sites (Petit et al. 1989, Waite 1991 la), and concealing caches (Petit et al. 1989, Waite 1991a). The Gray Jay is a permanent resident of high-latitude boreal forests in North America. These birds store hundreds of food items per day during summer (Waite 1991a), and apparently rely heavily on that food during the winter (Waite 1990), when they have as little as 4 hr of foraging time available each day during which to accumulate energy reserves for the upcoming night of hypothermic fasting (Waite 199 ib, in press). Food items are cached as saliva-coated boli (Dow 1965), each of which is placed in a separate arboreal site, such as under a flake of bark, in a clump of lichen, or in a conifer needle-cluster.

Winter Fattening in Gray Jays: Seasonal, Diurnal and Climatic Correlates

Recent models of body mass regulation predict that small birds wintering under thermally stressful conditions should show increases in the dawn minima of their body mass and fat reserves with the approach of midwinter. This seasonal increase in energy reserves is hypothesized to function as insurance against the increased thermal demands during the short cold days of midwinter, when snowstorms can further reduce the already-deteriorating food supply. Superimposed on this winter fattening strategy, there should be a daily increase in the amount of fat stored for the coming night of fasting. To investigate patterns of variation in their body mass and fat reserves, Gray Jays Perisoreus canadensis were captured repeatedly near the northern limit of their range in Alaska between 7 September and 16 December 1987. As predicted, the dawn minima of body mass and fat stores tended to increase with the approach of midwinter. In addition, the results suggest that the jays increased their energy reserves later in the day, and that they facultatively increased their reserves in response to lower temperatures, heavier snowfall, and windier conditions. These results indicate that there was a seasonal increase in energy reserves associated with decreasing photoperiod, and that superimposed on this pattern was a daily cycle sensitive to contemporaneous climatic conditions. Thus, the jays appeared to have increased fasting capacity during those times when the risk of energetic shortfall was heightened.

Gray Jay Scatterhoarding Behavior, Rate Maximization, and the Effect of Local Cache Density

A model is presented that concerns how a scatterhoarder should distribute food items taken from an ephemeral, locally abundant source among cache sites scattered throughout its territory, and how such an animal should adjust the way it distributes its caches in response to the presence of previously made caches. The model assumes that such an animal behaves in a manner that maximizes the rate at which recoverable (surviving) food energy is stored. One application of this model concerns how a scatterhoarder should respond when it encounters a food source in the same location as a previously exploited one. Such spatial overlap of food sources through time may be a common occurrence for animals such as Gray Jays Perisoreus canadensis which store thousands of food items throughout their territory during the summer months for use during winter. Under the conditions of the experiment, but not under all theoretical conditions, the model predicts that Gray Jays should space their caches more widely during subsequent encounters with a source at a given location. Consequently, they should take longer to cache a given number of food items, and, because fewer of these caches will survive, the number of recoverable caches made per unit of time spent caching should be reduced. A field experiment using Gray Jays is described. As predicted, jays compensated for the local density of extant caches by transporting food items farther from the source during second encounters with a source in a given location. These results indicate that the jays, at least for the conditions of this experiment, are not forced by a memory constraint to behave in some standard fashion when they encounter a point food source. The theoretical and empirical results begin to show how scatterhoarders, by flexibly adjusting their behavior in response to previously made caches, may approach the maximal rate of storage of recoverable food throughout their territory over the long term.

Caching Behaviour in the Gray Jay and the Source-Departure Decision for Rate-Maximizing Scatterhoarders

AbstractWe developed a model that concerns, in part, how long a scatterhoarder should persist in caching food from an ephemeral, locally abundant source ('bonanza') before moving on in search of other sources. The model assumes that an animal scattering food caches for later use behaves in a manner that maximizes the rate at which it stores recoverable (surviving) food in its habitat. It is shown theoretically that under some conditions it is better not to cache all available food but instead to move on in search of other food sources. This 'source-departure decision' for scatterhoarders is analogous to the patch-departure decision for animals that forage among food patches. It is shown that whether, and at what point, a 'moving-on threshold' is reached should depend on the size of the source, the strength of density-dependent cache theft, and the abundance of sources in the habitat. A field experiment was performed to test the qualitative prediction that gray jays, Perisoreus canadensis, should not persist as long in caching food when a day-long opportunity for caching is restricted to a single source (single-source treatment) as when such an opportunity is divided among a series of disjunct sources (multiple-source treatment). In the single-source treatment, jays tended to cache at lower overall rates, transport food items to more distant cache sites, and spend less time caching. These tendencies became more pronounced later in the day. However, although the rate of caching approached zero in the single-source treatment, the jays did not completely cease caching. This apparent violation of the model is attributed to the behaviour of recaching, a facet of gray jay scatterhoarding behaviour that was not built into the model. This retrieval and redistribution of previous caches resulted in the stabilization of the density of caches near the source. In addition, this switch from single- to multiple-load caching trips arguably would make it economical for gray jays to continue to make caching trips from a source beyond the source-departure point predicted by the model. Our theoretical and empirical results begin to show how scatterhoarders may behave in a manner that maximizes the long-term average rate of storage of recoverable food energy throughout their habitat.

Juvenile dispersal in Gray Jays: dominant brood member expels siblings from natal territory

Breeding pairs of Gray Jays (Perisoreus canadensis) in Quebec and Ontario were accompanied in the autumn significantly more often by one nonbreeder, and less often by none or two, than expected from initial brood size frequencies. Among the rare cases of two nonbreeders accompanying a pair, there was no evidence that both were from the same brood. These observations, and the fact that 30.6% of single nonbreeders closely associated with autumn pairs of known, same-year breeding history were unrelated to those adults, indicated the division of juvenile Gray Jays into "stayers," which remained with their parents at no more than one per pair, and "leavers," which left their natal territory and sometimes joined an unrelated pair. The weight distribution of 62 stayers indicated that about two-thirds were males. Leavers had a more equal sex ratio and showed a strong tendency to associate with failed breeders. Stayers apparently had much higher first-summer survival than leavers but no significant chance to inherit their natal territory. Gray Jay broods broke up in June, through intrabrood aggression, when the young were 55–65 days old. Stayers were the dominant juveniles that forced out the leavers. Partial June dispersal may function as a type of brood reduction that permits the dominant juvenile to have exclusive access to a parental subsidy of stored food that is reliably adequate for the survival of only one extra bird on the territory. The best models describing the origin and winter acquisition of such a subsidy postulate recovery of stored food by memory and require that the expulsion of subordinate siblings occur at the beginning of the food storage season. The models predict that food stored by Gray Jays in June survives in significant enough quantities to enhance winter survival.

Nocturnal Hypothermia in Gray Jays Perisoreus canadensis Wintering in Interior Alaska

Radio-telemetry measurements were made of deep body temperature (Tb) in winter acclimatized Gray Jays Perisoreus canadensis held in an outdoor aviary at 66040'N, 150'33'W between 3 December 1987 and 29 January 1988. The diurnal rhythm of Tb was similar among the three individuals tested. Upon roosting for the night, the birds experienced a gradual drop in Tb until about 0500-0700 hours. Tb then levelled off until approximately 0800 when it began to rise sharply to the usual daytime level just before the birds became active. In contrast to a previous study which failed to demonstrate any appreciable nocturnal hypothermic response in a winter-acclimatized Gray Jay, the birds tested in the present study dropped their body temperature at night substantially (range: 4.5 6.1?C) below their mean daytime temperature of approximately 42'C. Moreover, the extent of the hypothermic response was correlated with the minimum overnight air temperature; on colder nights the jays tended to drop their body temperature to a greater extent. These results suggest that Gray Jays may save appreciable amounts of energy during the long, cold nights of the arctic winter as a result of their hypothermic response.

Effects of Caching Supplemental Food on Induced Feather Regeneration in Wintering Gray Jays Perisoreus canadensis: A Ptilochronology Study

The technique of ptilochronology was used to assess the influence of food cache availability on feather regeneration in Gray Jays Perisoreus canadensis wintering in northcentral Alaska (66'40'N, 150033'W). The method involved plucking a rectrix (tail feather), allowing the bird to grow a replacement feather from the same follicle, plucking that induced feather, and then measuring the width of daily growth bars and the length and mass of the induced feather. The experimental protocol involved supplementing jays in some territories with food that they were allowed to cache, and leaving jays in other territories unsupplemented. After the period of food supplementation, a rectrix was taken from jays in all territories. Approximately two months later, the induced (replacement) rectrix was taken from jays in all territories. Replacement feathers from jays with supplemental caches grew at a faster rate and were longer and heavier than those from jays that did not have access to supplemental caches. Supplemented jays were also more likely to grow a replacement feather. These results suggest that the wintering jays with access to more cached food were able to allocate a greater amount of energy to feather growth. Ptilochronology appears to have promise for improving the experimental tractability of a great variety of questions in avian ecology.

The behaviour of grey jays, Perisoreus canadensis, towards palatable and unpalatable Lepidoptera

Grey jays were fed a set of six species of lepidopterans, predicted to be palatable or unpalatable based on their coloration and the fate of ingested host plant allelochemicals. Each of four birds received the entire series of insects. Junonia coenia (Nymphalidae) and Ceratomia catalpae (Sphingidae) were highly palatable as predicted based on their relatively cryptic coloration and lack of chemical defence. Three Euphydryas (Nymphalidae) species were predicted to be unpalatable: larvae and adults are warningly coloured and they sequester iridoid glycosides. However, Euphydryas gillettii was quite palatable, E. anicia was intermediate and E. phaeton was unpalatable. These differences may be due to differences in the iridoid glycoside content of these butterflies. Eumaeus atala (Lycaenidae) sequesters cycasin from its hostplant in the Cycadaceae and larvae and adults are warningly coloured. Adult E. atala were unpalatable.

Risk-prone foraging behaviour in captive grey jays, Perisoreus canadensis

Grey jays were allowed to forage in a two-patch, closed-economy laboratory operant simulation of bark-gleaning foraging behaviour. Each patch exhibited identical mean variable ratio schedules (prey densities) but differed in variances around the mean. Four prey densities were used, ranging from very high density to a density demonstrated to provide a negative energy budget. Jays that did not develop side biases consistently foraged in high variance patches, exhibiting risk-prone behaviour. Time of day did not influence risk-sensitive foraging patterns. Several possible explanations for this behaviour are explored including body size, closed economy effects and the influence of the perception of prey value discounted by delay.

Animal vectors of Arceuthobiumamericanum seed in Manitoba

Long-distance dispersal of Arceuthobiumamericanum Nutt. ex Engelm. seed by animals was investigated in Grand Beach Provincial Park, Manitoba, where passerine migration routes traverse stands of dwarf mistletoe infected Pinusbanksiana Lamb. Small mammals appear to be insignificant as vectors in Manitoba as no seeds were found on any of the 193 individuals trapped. In contrast, 5.5% of 146 birds netted in 1986 and 5.1% of 59 netted in 1987 carried seed. Three species are reported carrying seed for the first time: brown creeper (Certhiaamericana), Swainson's thrush (Catharusustulatus), and red-breasted nuthatch (Sittacanadensis). Seeds were also found on five gray jays (Perisoreuscanadensis) and three dark-eyed juncos (Juncohyemalis), species for which numerous records of dwarf mistletoe seed transport already exist. Swainson's thrushes and dark-eyed juncos are potential disseminators of A. americanum seed into jack pine stands in northern Ontario and the Great Lakes States during years when seed discharge and migration overlap.

Gray Jays, Perisoreus canadensis, and Common Ravens, Corvus corax, as predators of Winter Ticks, Dermacentor alhipictus

Gray Jays, Perisoreus canadensis, and Common Ravens, Corvus corax, as predators of Winter Ticks, Dermacentor alhipictus

A Field Test of Density-Dependent Survival of Simulated Gray Jay Caches

Journal Article A Field Test of Density-Dependent Survival of Simulated Gray Jay Caches Get access Thomas A. Waite Thomas A. Waite Department of Zoology, The Ohio State University, Columbus, OH 43210 Search for other works by this author on: Oxford Academic Google Scholar The Condor, Volume 90, Issue 1, 1 February 1988, Pages 247–249, https://doi.org/10.2307/1368458 Published: 01 February 1988 Article history Received: 20 March 1987 Accepted: 08 July 1987 Published: 01 February 1988

Predation, thermoregulation, and wing color in pierid butterflies.

This paper explores two hypotheses about the relationships among predation, thermoregulation, and wing color in butterflies: First, that butterflies are susceptible to predation during thermally marginal periods (e.g., cool weather) when effective thermoregulation and flight are not possible; second, that Pieris butterflies are relatively unpalatable to visual predators, supporting the idea that the white wing pigment of Pieris represents aposematic coloration. Field experiments with Pieris and Colias in 1984 and 1985 demonstrate that substantial predation may occur during the morning period before butterflies are able to actively fly. Circumstantial evidence is presented to suggest that at least some of the predation is by small, cursorial mammals. Feeding experiments in the field using Grey Jays as predators indicate that Pieris napi and P. occidentalis are less palatable than other sympatric butterflies, including confamial Colias alexandra. These and previous results suggest that Pieris are edible but less preferred as prey by birds, and that the degree of palatibility may vary among Pieris species. The relatively low palatability of these Pieris is consistent with the hypothesis that their white pigmentation represents aposematic coloration; however, the cues by which potential bird predators might discriminate against Pieris have not been established.

Factors Affecting Food Choice by Gray Jays

Factors Affecting Food Choice by Gray Jays

Bolus recovery by gray jays: an experimental analysis

Gray jays ( Perisoreus canadensis) typically store food boli in various sites on conifers. In a laboratory setting we determined whether gray jays recover stored boli by means of olfaction, trial-and-error search or spatial memory. Using an artificial tree with 52 possible caching sites, caching and/or recovery trials were performed with five captive gray jays for the following experiments: (1) no extra visual cues on tree; (2) extra visual cues (pine foliage) attached to tree; (3) pungent-smelling food hidden by observer; (4) one bird allowed to cache food but caches recovered by a second bird; (5) one bird allowed to observe another bird cache food and later permitted to recover those caches. Results supported the memory hypothesis, but cache site preferences were apparent for individual birds. To control for this, an additional experiment (6), in which cache site access was limited by the investigators, was conducted with two new birds. These results also indicated that gray jays use spatial memory to recover stored boli.

Steller's Jays Steal Gray Jay Caches: Field and Laboratory Observations

Steller's Jays Steal Gray Jay Caches: Field and Laboratory Observations

Predation by Gray Jays on Aggregating Tadpoles of the Boreal Toad (Bufo boreas)

Predation by Gray Jays on Aggregating Tadpoles of the Boreal Toad (Bufo boreas)

SELECTIVE PREDATION OF GRAY JAYS, PERISOREUS CANADENSIS, UPON BOREAL CHORUS FROGS, PSEUDACRIS TRISERIATA.

Wright (1948) pointed out that the conditions most favorable for rapid evolution exist when a species is divided into a large number of local populations, some of which are of small or medium effective size. Such conditions exist in the chorus frog, Pseudacris triseriata, in the mountains near Chambers Lake, Larimer County, Colorado. There are at least 21 breeding sites within a three mile radius among which exchange of individuals, and thus genetic interchange, occurs infrequently, if at all (Spencer, 1964). Eight phenotypes of dorsal coloration occur, and three loci, each with two alleles, are involved (Matthews and Pettus, 1966). Tordoff et al. (1976) demonstrated significant differences among seven of these populations in the frequencies of alleles controlling dorsal coloration. Tordoff and Pettus (1977) further demonstrated that phenotypic frequencies for any one of three of these populations remained nearly constant over a five year period of study, and that the populations had small to medium sizes, ranging from 37 to 580 adults estimated from recapture data using a modified Lincoln index (Bailey, 1952). Matthews (1971) and Hess (1969), working in montane and piedmont populations of chorus frogs respectively, concluded that changes in gene frequencies during the life cycle appear to be cyclic. One allele of a pair increases in frequency during the aquatic phase, and the other allele increases during the terrestrial phase of the life cycle. However, there appears to be little or no change from generation to generation. Tordoff and Pettus (1977) believed natural selection to be an important factor in maintaining the observed gene frequencies in these populations. Nevo (1973) drew similar conclusions for two other species of hvlid frogs, Acris crepitans and A. gryllus, and suggested that visual selective predation was one factor involved in maintaining the color polymorphism. In our montane populations, adults and recently metamorphosed young frogs are active during the day in mid and late summer and thus are susceptible to visual predation by diurnal predators. Gray jays, Perisoreus canadensis, are common in and around the meadows frequented by the frogs and they have been observed eating young frogs in these meadows. Visual selection of prey by various bird species has been demonstrated previously under both laboratory and field conditions. Isely (1938) and Dice (1947), in laboratory situations, demonstrated that various species of birds strongly selected against prey which contrasted with the soil color. Kettlewell (1955, 1956, 1965) observed different species of birds prey upon moths under natural conditions. In the majority of the cases, the birds selected the moth which contrasted with the background coloration. Research on mimicry in Lepidoptera has added greatly to our knowledge of visual selection by various bird species (Ford, 1964; Terhune, 1977). Cain and Sheppard (1954, 1961), Cameron (1969), Parkin (1971), and others have shown that birds selectively feed on land snails (Cepaea nemoralis, C. hortensis, Arianta arbustorum), with intensity of selection on different morphs being highly correlated with the degree of crypticity. The present study was undertaken to test, under laboratory conditions, whether gray jays would prey differentially on polymorphic chorus frogs exhibiting vary-

Gray Jay nesting in the Mer Bleue Bog, Ottawa, Ontario

Gray Jay nesting in the Mer Bleue Bog, Ottawa, Ontario