Mesopredator release and avifaunal extinctions in a fragmented system

Mammalian carnivores are particularly vulnerable to extinction in fragmente d landscapes', and their disappearance may lead to increased numbers of sma ller carnivores that are principle predators of birds and other small verte brates. Such 'mesopredator release'(2) has been implicated in the decline a nd extinction of prey species(2-6). Because experimental manipulation of ca rnivores is logistically, financially and ethically problematic(6,7), howev er, few studies have evaluated how trophic cascades generated by the declin e of dominant predators combine with other fragmentation effects to influen ce species diversity in terrestrial systems. Although the mesopredator rele ase hypothesis has received only limited critical evaluations and remains c ontroversial(9), it has become the basis for conservation programmes justif ying the protection of carnivores(6). Here we describe a study that exploit s spatial and temporal variation in the distribution and abundance of an ap ex predator, the coyote, in a landscape fragmented by development. It appea rs that the decline and disappearance of the coyote, in conjunction with th e effects of habitat fragmentation, affect the distribution and abundance o f smaller carnivores and the persistence of their avian prey.