Scale‐sensitive landscape complementation determines habitat suitability for a territorial generalist

Abstract

Evaluating habitat suitability is often complex, as habitat effects may be scale-dependent, critical resources may be spatially segregated, and resource availability may also depend on intra-and inter-specific interactions. Using analyses that spanned multiple years and spatial scales, we investigated habitat requirements of a territorial generalist, the common raven Corvus corax, in a relatively pristine woodland, Bial owieża Forest (E Poland). We compiled data from multiple raven surveys conducted between 1985 and 2001. Ravens were regularly distributed over the entire study area but declined in density over 50% within the 16 yr interval. In the same period game and forest management significantly reduced ungulate densities and likely diminished the habitat quality with regard to food supply, especially carrion. To better understand habitat requirements of ravens we studied breeding performance in relation to three different habitat types across multiple scales: open areas, coniferous-dominated forest, and deciduous-dominated forest. We found a prominent dissimilarity between raven nesting and foraging habitats highlighting the importance of resource complementation for ravens. On a fine scale, large old pines were exclusively selected as nesting trees and nesting areas were generally coniferous-dominated. However, at increasingly broader scales, coniferous habitats were negatively associated with raven reproductive success as those habitats likely provide a lower food supply. Only where the coniferous nesting areas at smaller scales were complemented with high percentages of deciduous forests and open areas at broader scales did the breeding performance increase. In addition to habitat composition, intra-specific interactions were important determinants of reproductive performance and very successful neighbors decreased reproductive performance of a focal pair. Most of previous studies have investigated resource complementation in terms of habitat edges or proximity of complementing resource patches. Our study demonstrates that the concept of landscape complementation also applies to gradients in landscape composition and emphasizes the importance of scales and intraspecific interactions in habitat analyses.

Biotic and multi-scale abiotic controls of habitat quality: their effect on coral-reef fishes

“…We demonstrated that the nested microhabitat and plot-scale variables both appear to significantly influence habitat quality for reef-associated fishes, but the effects varied among components of the fish community and plotscale coral density was only correlated with the abundance of adult fishes. The importance of assessing habitat quality at multiple scales has been recognised in a variety of ecosystems including woodland birds (Mueller et al 2009 Despite the growing recognition of the importance of both abiotic and biotic controls of habitat quality, an analysis of 173 ornithological studies demonstrated that only 6% considered how constraints such as predation or competition affected habitat quality (Johnson 2007). Our study adds to the literature on abiotic and biotic controls of habitat quality in reef fishes by demonstrating how both the competitive effects of territorial damselfishes and abiotic habitat quality are correlated with the abundance of reef-associated species.…”

“…Evaluating how individuals of a species respond to varying habitat quality is complex because of scale-dependent responses and the combined influence of biotic and abiotic factors (Mueller et al 2009). This study supports the growing recognition that both biotic variables and scale-dependent effects must be considered when assessing habitat quality, which traditionally assesses only abiotic variables and is measured at a single scale.…”

“…Franklin et al 2000, Fleishman et al 2002. Despite its importance, assessing habitat quality is frequently problematic because it requires an understanding of a range of biotic and abiotic factors that may vary at multiple spatial and temporal scales, and may change during an organism's ontogeny (Mueller et al 2009). Consequently, there is a growing literature considering habitat quality through a combination of biotic and abiotic factors (e.g.…”

“…Shima et al 2008), habitat quality at different scales (e.g. Mueller et al 2009), and how habitat quality affects different age classes of species (e.g. Bacheler et al 2009).…”

Identifying priority conservation areas for the American burying beetle,Nicrophorus americanus(Coleoptera: Silphidae), a habitat generalist

“…A comparison of two habitat generalist and specialist plants showed the habitat generalist species could not be successfully modelled because of inconsistent results for variables when using different model methods and overall low model performance when compared with the specialists' model performance (Evangelista et al, 2008). In contrast, Mueller et al (2009) found that generalist crows could be successfully modelled when different habitat designations and spatial scales were considered. Grey wolves are a wide-ranging habitat generalist with the potential to have conflicts with humans and livestock.…”