Investigating factors that set the lower elevational limit of Canada Jays (Perisoreus canadensis) on Vancouver Island, British Columbia, Canada

Abstract

The biotic and abiotic factors responsible for determining ranges of most species are poorly understood. The Canada Jay (Perisoreus canadensis (Linnaeus, 1766)) relies on perishable cached food for over-winter survival and late-winter breeding and the persistence of cached food could be a driver of range limits. We confirmed that the Canada Jay’s lower elevational limit on Vancouver Island, British Columbia, Canada, matches that of the subalpine zone (900 m) and then conducted simulated caching experiments to examine the influence of antimicrobial properties of subalpine tree species (biotic) and of temperature (abiotic) on the preservation of cached food. We found that two high-elevation species, yellow cedar (Callitropsis nootkatensis (D. Don) D.P. Little) and Amabilis fir (Abies amabilis Douglas ex J. Forbes), preserved cached blueberries and chicken flesh better than other trees, but they also occurred well below the lower limit of Canada Jays. The effect of temperature was similarly unclear; while food cached at 1150 m retained 17% more mass than food cached at 550 m, there was no difference in percent mass remaining of food placed 70 m above versus 120 m below the Canada Jay’s lower elevational limit. Thus, we were unable to provide definitive evidence that either of the proposed abiotic or biotic factors was responsible for setting thelower elevational limit of resident Canada Jays.