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NSW Bird Atlas data: more woodland species in trouble

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NSW Bird Atlas data: more woodland species in trouble 2016-12-07T00:32:36+00:00

NSW Bird Atlas data: more woodland species in trouble

Stephen Debus

The recently released Atlas of the Birds of New South Wales and the ACT volumes 1 and 2 (2014, 2016, NSW Bird Atlassers) reveal some further worrying trends for certain forest and woodland birds.  Comparisons between the first and second national bird atlassses revealed some downward trends at both a national and state level (see the Birds Australia Atlas 2 book, and also Barrett et al. 2007, Australian Zoologist 34: 37–77 for NSW specifically).  Despite the changed survey methods in national Atlas 2, the data resulted in two waves of woodland birds being added to the NSW Threatened Species Conservation Act as Vulnerable (the first group being largely based on national Atlas 2, the second on Barrett et al. 2007).  However, many of those species are birds of the temperate and subhumid grassy woodlands of the eastern sheep–wheat belt.  The NSW Bird Atlas continued the method of national Atlas 1, and analysis was for the period 1986–2006.  Considering just the species covered in NSW Atlas vols 1 and 2 (up to the thornbills and whitefaces in the taxonomic sequence), it is apparent that another dozen or so forest and woodland species could bear consideration for Vulnerable listing under the TSC Act.

Using the generation times calculated for the 2010 Action Plan for Australian Birds by Garnett et al., and the formula used by the NSW Scientific Committee for calculating % decline over three generations, these species would qualify for Vulnerable in NSW under the IUCN threshold (as used by the NSW Scientific Committee) of greater than 30% decline in index of abundance (i.e. atlas reporting rate, RR) over three generations.  Using the annual RR graphs in NSW Atlas vols 1 and 2, and estimating by eye a line of best fit for those species with sufficient data showing an approximately 50% linear decline in RR over 20 years at a high significance level (P <0.001 or P<0.0001), those species are (with their calculated % decline in RR over three generations):

  • Spotted Nightjar 41%
  • Australian Owlet-nightjar 41%
  • Yellow Rosella 46%
  • Blue Bonnet 41% (even taking into account western NSW data only)
  • Mulga Parrot 34% (even taking into account western NSW data only)
  • Red-backed Kingfisher 41% (even taking into account western NSW data only)
  • Rainbow Bee-eater 46%
  • Red-browed Treecreeper 52%
  • Splendid Fairy-wren 56%
  • Pilotbird 52%
  • Rockwarbler 41%
  • Chestnut-rumped Thornbill 46%
  • Inland Thornbill 46%
  • Southern Whiteface 41%

These declines in RR are necessarily approximate, but all exceed the 30% threshold over three generations.  Several even approximate the IUCN/NSW Scientific Committee threshold for Endangered (>50% decline in 3 generations).  It is immediately apparent that these birds group in several categories:

  • Eastern forest species, some terrestrial (including for nesting) or partly so, or hollow-dependent, variously affected by forest clearance, logging, fire (wildfire and prescribed) or introduced predators (cats, foxes), or a combination of these (Owlet-nightjar, Red-browed Treecreeper, Pilotbird, Rockwarbler)
  • Hollow-dependent species of inland riverine or other woodlands (Owlet-nightjar, Yellow Rosella)
  • Hollow-dependent, ground-foraging seed-eaters of mainly native vegetation in the semi-arid zone (Blue Bonnet, Mulga Parrot)
  • Ground-nesters (litter in semi-arid woodlands, tunnels in river banks and riparian zones), one also a perch-pounce ground forager in semi-arid woodlands (Spotted Nightjar, Red-backed Kingfisher, Rainbow Bee-eater)
  • Ground- or shrub-foraging insectivores of native vegetation in the semi-arid zone (Splendid Fairy-wren, Chestnut-rumped and Inland Thornbills, Southern Whiteface)

Other than the few eastern forest species listed above, the common theme is habitat quality in the semi-arid woodlands, be it River Red Gum on inland rivers or the quality of the tree (e.g. hollows), ground and shrub layers in the western woodlands generally.  It is apparent that as well as the decliners in the temperate grassy woodlands, we should be concerned about the decliners in the semi-arid woodlands where their habitat elements are under ongoing threats from habitat clearance and degradation, long-term overgrazing, water deprivation, and the effects of drought.  Admittedly, the analysis spanned a drought period, and conditions have improved since.  Even so, under climate change and its prospect of longer and more frequent droughts, and longer and hotter fire seasons, it seems unlikely that these species will bounce back to their former numbers during wet cycles, even if some ‘boom-bust’ arid-zone species do.

Furthermore, the NSW Bird Atlas data vindicate many of the prior Vulnerable listings in the TSC Act that were based on national Atlas1/Atlas 2 comparisons, and suggest that a few of those could even be upgraded to Endangered.  The data also vindicate the assessment of a few in the above list as probably Vulnerable in 2008 (the last official review of the TSC Act schedules), but which avoided (or were declined) listing in that truncated review.  It remains to be seen which western woodland passerines in NSW Atlas vol. 3 will also exceed the 30% decline in RR in three generations.  One can anticipate perhaps another dozen or so species that are dependent on some aspect of habitat quality (notably the shrub and ground layers) in the semi-arid woodlands.  However, given funding levels, it will probably take citizen nominations (and a laboriously long time – perhaps too long for some species), rather than OEH internal review, to achieve realistic listings by the Scientific Committee.

And governments just don’t get it.  Many detailed and thorough critiques have been lodged concerning the NSW Government’s proposed gutting of environmental legislation (TSC Act and Native Vegetation Conservation Act).  Paraphrasing those critiques, suffice it to say here that the proposed legislation is a sell-out to developers; is clueless about the drivers of biodiversity decline, and of farmland and water degradation; contains laughable or non-transparent proposals on offsetting, biobanking, self-assessment/self-regulation by developers, and the integrity of conservation agreements; invites corruption; ignores climate change; and is accompanied by draconian legislation attacking democracy and citizens’ rights to contest bad proposals (while easing the path and penalties for environmental vandalism).

Stephen Debus
From; Birds NSW Newsletter, NSW Bird Atlassers
N0. 131 September 2016 pages 5-6