Hierarchical Mechanisms of Fruit Selection by an Avian Frugivore
Hierarchical Mechanisms of Fruit Selection by an Avian Frugivore
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鸟类食果动物水果选择的层次机制
DOI：
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发表时间：
1993
期刊：
影响因子：
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通讯作者：
R. Sallabanks
中科院分区：
文献类型：
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作者：
R. Sallabanks
为了探讨果实选择的行为机制，研究了美洲知更鸟(Turdus Migratorius)在西部或-埃贡地区捕食山楂果实的行为机制。知更鸟面临着水果选择的分级决策过程：(1)喂哪种灌木(在灌木中决定)；(2)采摘哪种水果(水果之间的视觉决定)；(3)一旦采摘就吞下哪种水果(账单内的决定)。对自然种群和人工栽培种群的田间观察表明，知更鸟在灌木中的选择与三个植物性状(决策线索)相关：果实丰富度、果实大小和果肉。这些线索本身是按等级使用的，所以当通过操纵灌木保持较高级别的线索不变时，下一个可用的线索就变得重要起来。一旦选择了灌木，田野和鸟类的研究表明，知更鸟随后会在与果实大小相关的水果中做出视觉选择。然而，没有发现证据表明知更鸟在账单内做出决定；一旦水果被采摘，就不会发生额外的歧视。我认为，水果选择的分级过程可能已经进化，使食果者能够应对环境的不确定性，这是果实系统的典型特征。这种觅食行为的灵活性本身可能会促进果树内部和之间的变异性，因此有助于解释为什么在果树-食果者关系中发现的一般模式如此之少。
To examine behavioral mechanisms of fruit selection, American Robins (Turdus migratorius) were studied foraging on Crataegus monogyna fruits in western Or- egon. Robins faced a hierarchical decision-making process of fruit selection: (1) in which shrub to feed (decisions among shrubs); (2) which fruits to pick (visual decisions among fruits); and (3) which fruits to swallow once picked (within-bill decisions). Field observations of natural and experimentally manipulated populations of C. monogyna shrubs demon- strated that choices made by robins among shrubs were correlated with three plant traits (decision cues): fruit abundance, fruit size, and fruit pulpiness. These cues were themselves used hierarchically, so that when higher-ranking cues were held constant by manipulating shrubs, the next available cue became important. Once shrubs were selected, field and aviary work revealed that robins then made visual choices among fruits correlated with fruit size. However, no evidence was found to suggest that robins made within-bill decisions; once fruits were picked, additional discrimination did not occur. I suggest that a hierarchical process of fruit selection may have evolved to enable frugivores to cope with environmental uncertainty that is typical of fruiting systems. Such flexibility in foraging behavior may, in itself, promote variability within and among fruiting plants and therefore help to explain why so few general patterns have been identified in fruiting plant-frugivore relationships.