Conservation management of eastern Australian farmland birds in relation to landscape gradients

Abstract

Summary1. Birds inhabiting farmland are of conservation concern around the world. In Australia, conservation management has focused primarily on woodland environments. By contrast, semi-natural open areas have received less attention. We argue that long-term conservation strategies should consider broad gradients of environmental conditions. Otherwise, there is a risk that semi-natural open areas will degrade through 'benign neglect', and currently common species using these areas will become uncommon. 2. We examined how birds responded to three environmental gradients in an Australian livestock grazing landscape: tree density, grazing intensity and nutrient enrichment. First, we investigated changes in species composition across the environmental gradients in multivariate space. Secondly, we modelled species richness and the response of selected individual species in relation to the gradients. Thirdly, we examined if there were patterns in guild composition and body mass distribution. 3. Tree density was the primary driver of virtually all patterns observed. Species richness peaked at moderately high tree densities. With increasing tree density, species composition changed, foraging guild composition changed and the median body mass of bird species decreased. Small insectivores were more likely to occur in areas with high tree densities, whereas large granivores were more likely to occur in areas with relatively low tree densities. Grazing intensity and nutrient enrichment were less strongly related to bird distribution patterns, although the indirect effects of these gradients may be substantial because they affect tree regeneration. 4. Synthesis and applications. Relatively dense woodland patches were important for species already of conservation concern, lending support to their active conservation management, for example through livestock exclusion. However, semi-natural open areas also were used by many birds, which represented a different mix of body sizes and foraging guilds. Scattered trees occurring at a range of densities are key habitat elements in semi-natural open areas. However, many scattered trees are dying and are not being replaced by natural regeneration or tree planting. If areas with scattered trees continue to degrade, there is a risk that currently common farmland birds will decline. Management strategies aiming to maintain scattered trees therefore are important, including the planting of individual trees and the adoption of grazing practices that allow for natural tree regeneration.

High trees increase sunflower seed predation by birds in an agricultural landscape of Israel

“…Because birds were the main sunflower seed predators in our study area, our results agree with the findings of Hanspach et al (2011) who found that scattered trees were key habitat structures for birds in semi-natural open areas. We observed flocks of a few hundreds of birds of the Rose-Ringed Parakeet in our study area, (Personal Observation and reports by local farmers) (Figure 1), one of the main bird pests to agriculture in Israel (Nemtzov, 2003).…”

Impacts of agricultural intensification on bird communities: New insights from a multi-level and multi-facet approach of biodiversity

“…Overall, the diet of species might be a relevant trait to explain species assortment in intensive agriculture. However, the species trophic category (STI) was not involved in the beta diversity decline, suggesting that species replacement, and/or dissimilarities derived from nestedness, do not depend on the species position within the trophic network but maybe rather on the vegetation layer of foraging (Hanspach et al, 2011). By extension, all trophic levels can be affected by agricultural intensification.…”

“…Similarly, a Community Trophic Index (CTI), adapted from the Marine Trophic Index (Pauly and Watson, 2005), has been proposed as a surrogate of the potential trophic complexity within bird communities (Jiguet et al, 2012). This index has not yet been tested in agricultural landscapes, though these have been shown to favour granivorous and ground insectivorous species, leading to less diversified diet composition in farmland than in forested areas (Hanspach et al, 2011).…”

“…Tillage and pesticide use and landscape homogenization (Hanspach et al, 2011) were expected to disfavor ground feeders (by resource decrease), narrowing the diet complexity in farmland communities, and consequently, the species richness.…”

Implications of vegetation clearing biases for the interpretation of landscape-scale species-area relationships

“…Fire is an important driver of the occurrence of birds in Australian woodlands and forests, given its influence on the age and structure of vegetation Burgess & Maron, 2015;Haslem et al, 2016). Scattered paddock trees (Fischer et al, 2010b;Hanspach et al, 2011), and regrowth vegetation (Bowen et al, 2009b;Smallbone et al, 2014) have also been shown to affect the spatial composition of bird communities, due to the habitat resources they provide as a complement to remnant native vegetation.…”