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Acorn Harvesting by Florida Scrub Jays

Author:
DeGange, Anthony R., Fitzpatrick, John W., Layne, James N., Woolfenden, Glen E.
Source:
Ecology 1989 v.70 no.2 pp. 348-356
ISSN:
0012-9658
Subject:
Aphelocoma coerulescens, age structure, arthropods, breeding, crops, fruits, habitat preferences, habitats, harvesting, juveniles, shrublands, shrubs, summer, territoriality, warehouses
Abstract:
We documented number of acorns eaten, cached, and retrieved by Florida Scrub Jays (Aphelocoma coerulescens coerulescens), through one full annual cycle and part of another, in an oak scrub habitat characterized by abundant and reliable annual acorn crops. Jays consumed acorns during all months, with highest consumption from September through February and lowest in June and July. From August through December, most acorns consumed by jays were picked directly from shrubs; during the remaining 7 mo, acorns were recovered from ground stores. Acorn caching occurred throughout the fall, peaking in September and October. Data pooled across sex and age classes suggest that individual jays, on average, each cached between 6500 and 8000 acorns during fall of 1974. Only about one—third of those acorns were recovered later. Intact acorns recovered by Scrub Jays during fall usually were reburied, but by summer most recovered acorns were consumed. Acorn crops in the study area exhibit moderate annual variation but no crop failures. Acorns are available in substantial numbers every year, permitting Florida Scrub Jay territories to serve without fail as year—round warehouses of stored acorns. Those stores provide resources to carry group members through seasons of low arthropod availability, and perhaps facilitate delayed dispersal by juveniles. Use of a habitat characterized by relatively large and dependable annual acorn crops that are evenly dispersed, coupled with caching behavior, may contribute to the maintenance of permanent territoriality and cooperative breeding in this population.
Agid:
5188266