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Abstract
<p xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" class="first" dir="auto"
id="d989461e69">Blue jays consume large quantities of acorns to fuel energy-demanding
caching flights
in the fall. Yet blue jays possess no known physiological adaptation to counter the
negative effects of a high tannin diet on protein digestion. Dietary experiments were
conducted to determine if blue jays could subsist on an acorn-only diet, and if they
could not, to determine whether supplements of acorn weevil larvae (Curculio), present
inside acorns, enabled them to maintain their mass. Comparative tannin assays also
were conducted on Lepidobalanus (low tannin; white oak) and Erythrobalanus (high tannin;
pin oak) acorns using radial diffusion assay. Captive jays consumed considerable acorn
material, yet were unable to maintain mass on ad lib. acorn-only diets or on an acorn
+1.5 g larvae/day supplement. There were no significant differences in mass loss between
high and low tannin diets. In contrast, blue jays were able to stabilize mass on a
diet of acorns +5.0 g larvae supplement/day. These results suggest that acorn weevil
larvae, or perhaps other insects, counteract the effects of acorn tannins in the jay
diet allowing jays to subsist largely on acorns during the fall caching season. Oak
demographic processes may be partly regulated by a tri-trophic relationship among
plant, insect and bird. Acorn weevil larvae, considered damaging to oak populations,
may actually facilitate oak recruitment and population vagility in the long-term.
</p>