Does Seed Packaging Influence Fruit Consumption and Seed Passage in an Avian Frugivore?

(Uploaded by Plazi for the Bat Literature Project) Seed packagingis one fruitcharacteristicthatmay influencepost-ingestional fruitprocessingin avian frugivores.We tested the responseof a facultativefrugivore,the Silvereye(Zosteropslateralis),to fruitcontainingdifferentformsof seed packaging.Wildcaught,captive Silvereyes were presentedwith artificialfruit containingeitherone large seed or three small seeds of equivalenttotal volume, and their consumptionrates were recordedover90 min.In a secondexperiment,the seed transittimes(ingestionto excretion) for similarlarge-seededand small-seededfruitconsumedby Silvereyeswererecorded.Silvereyesconsumedsignificantlymore large-seededfruitthansmall-seededfruit.The transit time of seeds was also significantlyshorterfor large-seeded(mean = 22 min) than for small-seededfruit(mean= 29 min).Thusseed packaginghada significantinfluenceon the rateat whichfruitwereprocessed.Silvereyeswereable to consumemorelarge-seededthan small-seededfruitbecausethe seeds in large-seededfruitwere defecatedfasterthanthose in small-seededfruit.It is likely that Silvereyescan compensatefor the costs of seed ingestion throughhavinga rapidgut passagerateand hence an increasedfruitconsumption rate.The gut of Silvereyesshowed morphologicalcharactersintermediatebetweeninsectivores andspecialistfrugivores.The dimensionsof the intestineandgizzardwerelike those of insectivoresand the gizzardwas substantiallylargerthanthose of specialistfrugivores. Facultativefrugivoresappearto have few morphologicaladaptationsto frugivoryand we arguethatthis facilitatesplasticityin the diet andthe processingof insectswhenfruitis not available.