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Introduction in the region, population declines and the local extinction of birds are highly probable AIdo Leopold wrote that habitat conservation (Levey and Stiles, 1994). The local extinction requires that we save 'every cog and wheel' of anyone of these species might significantly (Leopold, 1949). The basis for his statement is alter recruitment patterns of these plants and, that species interact in ways both positive and over the long term, influence plant community negative, direct and indirect. When interacstructure. Here, we investigate how extinction tions are strong, loss of one species may affect offo~r avian frugivores might affect four shrub abunda~ce of other species in the community specIes. whose fruits are commonly eaten by (e.g. Paine, 1966; Terborgh, 1986). Diffuse these birds. We evaluate the potential impacts interactions, although much less strong, may of frugivore loss by comparing seed shadows a!so affect species' abundances and distribup~oduced by the existing frugivore community tJons. Seed dispersal by animals is an example ~th seed shadows that we predict would result of a diffuse interaction, because many animals if one or more bird species were extinct. We typic.ally disperse the seeds of a given plant ~hen modi~ predicted seed shadows by impo~ specIes (e.g. McDiarmid et aL, 1977; Lambert, mg four different seed-survival models. If the 1989). It is also an important mutualism, especurrent frugivore community creates a significially in tropical wet forests (Gentry, 1982). In cantly different spatial distribution of di~ this chapter we explore the potential consepersed seeds from that created by a community quences to plants of losing one or more seedthat lacks one or more frugivores, then extincdispersers from the community in a system tion of those frugivores may result in qualitative characterized by diffuse interactions between and quantitative changes to plant recruitment fleshy-fruited plants and fruit-eating birds. patterns. Thus, this study provides a glimpse In tropical wet forests of Costa Rica, a of how plant populations might be altered relatively small set of avian frugivores remove following extinction of one or more species and disperse most seeds of some understorey of frugivorous birds. shrubs (Loiselle and Blake, 1990, 1999). Given We start by providing a brief review of the large-scale disturbances that have occurred factors that influence how much plant