Understanding how long-term changes in climate influence populations requires knowledge of the mechanisms by which climate influences individual success and population abundance. We explored the implications of warmer falls and winters on a nonmigratory, food-caching bird, the Gray Jay (Perisoreus canadensis (L., 1766)), in Algonquin Park, Ontario, by experimentally examining the influence of temperature on the caloric content and mass of simulated cached food. Using three sites in, north of, and south of Algonquin, we examined the hypothesis that warmer temperatures would negatively influence the preservation of cached food by accelerating decay. Food cached at the highest latitude site retained the greatest mass and caloric content over 180 days of exposure, but there was no difference between the intermediate and the low latitude sites. We also show that Algonquin experienced a winter climate similar to our northernmost site as recently as 1990, and our results suggest that food availability in Algonquin has likely decreased since then, due to a warming climate. Interestingly, this coincides with a decline in territory occupancy by Gray Jays in Algonquin. Our results point to a unique mechanism by which climate warming may influence the persistence of a boreal species through its influence on winter food availability.
Measurement of neuron soma size by fluorescent Nissl stain
