Context-dependent seed dispersal by a scatter-hoarding corvid

dc.contributor.authorPesendorfer, Mario B.
dc.contributor.authorSillett, T. Scott
dc.contributor.authorMorrison, Scott A.
dc.contributor.authorKamil, Alan C.
dc.date.accessioned2016-04-07T11:33:17Z
dc.date.available2016-04-07T11:33:17Z
dc.date.issued2016
dc.description.abstractCorvids (crows, jays, magpies and nutcrackers) are important dispersers of large-seeded plants. Studies on captive or supplemented birds suggest that they flexibly adjust their scatter-hoarding behaviour to the context of social dynamics and relative seed availability. Because many corvid-dispersed trees show high annual variation in seed production, context-dependent foraging can have strong effects on natural corvid scatter-hoarding behaviour. We investigated how seed availability and social dynamics affected scatter-hoarding in the island scrub jays (Aphelocoma insularis). We quantified rates of scatter-hoarding behaviour and territorial defence of 26 colour-marked birds over a three-year period with variable acorn crops. We tested whether caching parameters were correlated with variation in annual seed production of oaks as predicted by the predator dispersal hypothesis, which states that caching rates and distances should vary with seed abundance in ways that benefit tree fitness. We also tested whether antagonistic interactions with conspecifics would affect scatter-hoarding adversely, as found in experimental studies. Caching behaviour varied with acorn availability. Caching distances correlated positively with annual acorn crop size, increasing by as much as 40% between years. Caching rates declined over time in years with small acorn crops, but increased when crops were large. Acorn foraging and caching rates were also negatively correlated with rates of territorial aggression. Overall foraging rates, however, were not associated with aggression, suggesting that reduced dispersal rates were not simply due to time constraints. Our field results support laboratory findings that caching rates and distances by scatter-hoarding corvids are context-dependent. Furthermore, our results are consistent with predictions of the predator dispersal hypothesis and suggest that large seed crops and social interactions among scatter-hoarders affect dispersal benefits for oaks and other masting tree species.
dc.format.extent798–805
dc.identifier0021-8790
dc.identifier.citationPesendorfer, Mario B., Sillett, T. Scott, Morrison, Scott A., and Kamil, Alan C. 2016. "<a href="https://repository.si.edu/handle/10088/28343">Context-dependent seed dispersal by a scatter-hoarding corvid</a>." <em>Journal of Animal Ecology</em>, 85, (3) 798–805. <a href="https://doi.org/10.1111/1365-2656.12501">https://doi.org/10.1111/1365-2656.12501</a>.
dc.identifier.issn0021-8790
dc.identifier.urihttps://hdl.handle.net/10088/28343
dc.publisherBlackwell Scientific Publishing
dc.relation.ispartofJournal of Animal Ecology 85 (3)
dc.titleContext-dependent seed dispersal by a scatter-hoarding corvid
dc.typearticle
sro.description.unitNZP
sro.identifier.doi10.1111/1365-2656.12501
sro.identifier.itemID139228
sro.identifier.refworksID69454
sro.identifier.urlhttps://repository.si.edu/handle/10088/28343
sro.publicationPlaceOxford, England

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