Longitudinal patterns in bird reporting rates in a threatened ecosystem: Is change regionally consistent?

摘要

Work in many parts of the world has discussed the decline of biodiversity in regions dominated by agriculture. We report the results of a major study documenting the longitudinal profiles of birds between 1998 and 2009 within 66 patches of temperate woodland in a heavily cleared and grazed agricultural region of south-eastern Australia. Many researchers have forecast the loss of bird biota from this region and others that also were formerly dominated by temperate woodland. We had sufficient high quality data to analyse the longitudinal profiles of reporting rates for 76 of the 116 individual bird species recorded in our 12-year study. Unexpectedly, only four of the 76 species analysed (5.6%) exhibited a significant negative linear decrease in reporting rate. More surprisingly, 32 (42.1%) exhibited a significant positive linear increase in reporting rate, including several taxa of conservation concern. These increases occurred despite a series of below-average rainfall years. Reporting rates were too low to formally model long-term trends in some other bird species widely considered to be of conservation concern such as the Diamond Firetail (Stagonopleura guttata) and Speckled Warbler (Chthonicola sagittata). Many authors have used functional (and other) groups to forecast bird species likely to be lost from Australia's temperate woodlands. However, we found no clear links between life history attributes and long-term trend patterns of species. Our findings contrast with recent findings from other temperate woodland-dominated regions in eastern Australia where losses in bird populations have been documented. However, they parallel other investigations such as in central New South Wales. These similarities among, and differences between, studies suggest regional differences in temporal patterns in bird population dynamics. Many of the observed changes in reporting rates were positive and they provide hope that forecast future losses of a large proportion of existing temperate woodland bird assemblages in south-eastern Australia may not be realised uniformly in all regions.