scholarly journals Apparent Predation by Gray Jays, Perisoreus canadensis, on Long-toed Salamanders, Ambystoma macrodactylum, in the Oregon Cascade Range

2005 ◽  
Vol 119 (2) ◽  
pp. 291 ◽  
Author(s):  
Michael P. Murray ◽  
Christopher A. Pearl ◽  
R. Bruce Bury
Keyword(s):  
Food Resource ◽  
Cascade Range ◽  
Temporary Ponds ◽  
Ambystoma Macrodactylum ◽  
First Report ◽  
Anuran Amphibians ◽  
Gray Jays ◽  
Perisoreus Canadensis ◽  
Aquatic Salamanders ◽  
Salamander Larvae

We report observations of Gray Jays (Perisoreus canadensis) appearing to consume larval Long-toed Salamanders (Ambystoma macrodactylum) in a drying subalpine pond in Oregon, USA. Corvids are known to prey upon a variety of anuran amphibians, but to our knowledge, this is the first report of predation by any corvid on aquatic salamanders. Long-toed Salamanders appear palatable to Gray Jays, and may provide a food resource to Gray Jays when salamander larvae are concentrated in drying temporary ponds.

Erroneous choice and foregone gains in hoarding gray jays ( Perisoreus canadensis )

2000 ◽  
Vol 3 (3) ◽  
pp. 127-134 ◽  
Author(s):  
T. A. Waite ◽  
K. L. Field
Keyword(s):  
Gray Jays ◽  
Perisoreus Canadensis

scholarly journals Weight-carrying Ability and Caching Behavior of Gray Jays, Perisoreus canadensis: Adaptations to Boreal Winters

2005 ◽  
Vol 119 (1) ◽  
pp. 101 ◽  
Author(s):  
Lynn L. Rogers
Keyword(s):  
Body Weight ◽  
Boreal Forest ◽  
Corvus Corax ◽  
Gray Jays ◽  
Risk Of Predation ◽  
Perisoreus Canadensis ◽  
Flight Loads ◽  
Insect Activity ◽  
Weight Carrying ◽  
Ability And Willingness

During 16 August to 21 September 1984, I determined how Gray Jays (Perisoreus canadensis) carried flight-loads of different weights. Three individually identifiable Gray Jays weighing 60, 68, and 80 grams, used their bills to carry flight-loads weighing up to 33 percent of bodyweight but transferred heavier flight-loads from their bills to their feet 1-2 meters after takeoff. They had difficulty carrying flight-loads over 57 percent of bodyweight, and none attempted to carry flight-loads over 66 percent of bodyweight. By using their feet to bring heavy flight-loads closer to the center of lift, Gray Jays can carry heavier loads of meat, relative to body weight, than can Common Ravens (Corvus corax) which compete with Gray Jays at carcasses in winter and which do not carry objects with their feet. During 1969-2003, year-round observations near the southern edge of the Gray Jay range in northeastern Minnesota showed that caching behavior begins in August, continues over-winter, and ends at the onset of insect activity and green-up in early May. Gray Jays’ propensity to approach larger animals, including people, may not indicate unwariness but rather a superior ability and willingness to assess risks and food benefits. In the boreal forest in winter, risk of starvation is greater and risk of predation is lower than in relatively food-rich ecoregions farther south.

scholarly journals A Nest Predator's View of a Managed Forest: Gray Jay (Perisoreus Canadensis) Movement Patterns in Response to Forest Edges

The Auk ◽  
2004 ◽  
Vol 121 (1) ◽  
pp. 162-169 ◽  
Author(s):  
Jacques Ibarzabal ◽  
André Desrochers
Keyword(s):  
Coniferous Forest ◽  
Movement Patterns ◽  
Forest Edge ◽  
Early Summer ◽  
Forest Edges ◽  
Artificial Nests ◽  
Gray Jays ◽  
Perisoreus Canadensis ◽  
Mature Stands ◽  
Nest Predators

Abstract High nest-predation risk is often associated with forest edges. Most nest predators in boreal coniferous forests of North America are forest specialists living in mature stands. Nest predators have been studied mainly through use of artificial nests; knowledge of their behavior remains limited. We used radiotelemetry to examine movement patterns, relative to forest edge, of a forest nest predator, the Gray Jay (Perisoreus canadensis), in boreal coniferous forest. Each of 11 family groups of Gray Jays monitored in early summer exhibited a marked association with forest edges. Jays were found within 30 m of the forest edges more often than expected from random use of mature forest. Furthermore, jays traveled more slowly near forest edges than in the forest interior. Because forest edges apparently represent prime foraging habitat for Gray Jays, narrow forest strips left by logging could act as ecological traps for mature-stand songbirds before stands regenerate in adjacent clearcuts.

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

Behaviour ◽  
1992 ◽  
Vol 120 (1-2) ◽  
pp. 51-67 ◽  
Author(s):  
Thomas A. Waite ◽  
John D. Reeve
Keyword(s):  
Average Rate ◽  
Food Sources ◽  
Single Source ◽  
Departure Point ◽  
Departure Decision ◽  
Gray Jays ◽  
Perisoreus Canadensis ◽  
Apparent Violation ◽  
Multiple Load

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

1991 ◽  
Vol 69 (12) ◽  
pp. 2935-2945 ◽  
Author(s):  
Dan Strickland
Keyword(s):  
Sex Ratio ◽  
Weight Distribution ◽  
Brood Size ◽  
Food Storage ◽  
Brood Reduction ◽  
Juvenile Dispersal ◽  
Storage Season ◽  
Unrelated Pair ◽  
Gray Jays ◽  
Perisoreus Canadensis

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.

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