Predators and avian community organization: an experiment in a semi-desert grassland

Abstract

We provide experimental evidence that predators are a major factor organizing a community of granivorous grassland birds (mostly emberizid finches). Our focus is not on the lethal effects of predators, but on the simple idea that (i) birds will not settle where they perceive a high risk of predation, and (ii) species differ in their perception of the safety of woody vegetative cover due to differences in antipredator escape behavior. Consistent with this idea is the fact that the composition of this grassland community responds markedly to minor manipulations in the distribution of woody cover. In particular, with the addition of cover to open grasslands, species with cover-dependent escape tactics increase in abundance, while the abundance of "cover-independent" species decreases greatly; this decrease may reflect aggression from cover-dependent species, but evidence suggests that some cover-independent species may actively avoid cover-rich areas per se. Non-predatory effects of cover, most notably those concerning food resources and microclimate, appear unable to explain these results. Predators may influence many communities of terrestrial vertebrates via species-specific responses to cover.

Breeding bird responses to juniper woodland expansion

“…The addition of a tree component provides nesting and foraging opportunities for woodland species, but reduces habitat suitability for grassland-obligate birds. The presence of woody vegetation may further influence community structure by altering predation risk for "cover-dependent" versus "coverindependent" bird species (Lima and Valone 1991).…”

Distribution, Abundance, and Habitat Characteristics of the Buff-Breasted Flycatcher in Arizona

“…Before provision of supplemental cover, chipping sparrows (Spizella pas.serina^ were absent from the study site, but were present after supplementary cover was provided (Lima and Valone 1991). In a like manner, habitat selection by buff-breasted flycatchers may be affected by the availability of a particular vegetation structure, plant species or group of species that provides this valuable esc^ cover.…”

Avian foraging behaviour in relation to provision of ecosystem services in a highland East African agroecosystem

“…Many of the apparent affinities for particular habitats reflect preferences for open versus closed habitats (Whelan et al 2008) and at its simplest, knowing whether a bird species is 'cover-dependent' or 'coverindependent' (Lima & Valone 1991) may provide a useful framework for determining where to plant particular crops that could potentially benefit or be damaged by a given species. The Speckled Mousebird, for example, is cover-dependent and is attracted to thick hedges and orchards.…”