Seasonal variation and the effects of drought on the abundance of arthropods in savanna woodland on the Northern Tablelands of New South Wales

Bell, H.L.

doi:10.1111/j.1442-9993.1985.tb00884.x

Cited by 43 publications

(34 citation statements)

References 9 publications

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“…Their decline signals mortality without replacement rather than movement. The abundance of arthropods, particularly those associated with the foliage of canopy trees, is greatly reduced during drought (Bell, 1985). Biomass of ground-litter invertebrates is linked to soil moisture (lower in drier soils) (Taylor, 2008), which, together with depletion of understorey vegetation, may explain strong declines in ground-feeding birds (Table 2).…”

Section: Discussionmentioning

confidence: 99%

Collapse of an avifauna: climate change appears to exacerbate habitat loss and degradation

Nally

Bennett

Thomson

et al. 2009

Diversity and Distributions

168

197

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Aim We characterized changes in reporting rates and abundances of bird species over a period of severe rainfall deficiency and increasing average temperatures. We also measured flowering in eucalypts, which support large numbers of nectarivores characteristic of the region.Location A 30,000‐km2 region of northern Victoria, Australia, consisting of limited amounts of remnant native woodlands embedded in largely agricultural landscapes.Methods There were three sets of monitoring studies, pitched at regional (survey programmes in 1995–97, 2004–05 and 2006–08), landscape (2002–03 and 2006–07) and site (1997–2008 continuously) scales. Bird survey techniques used a standard 2‐ha, 20‐min count method. We used Bayesian analyses of reporting rates to document statistically changes in the avifauna through time at each spatial scale.Results Bird populations in the largest remnants of native vegetation (up to 40,000 ha), some of which have been declared as national parks in the past decade, experienced similar declines to those in heavily cleared landscapes. All categories of birds (guilds based on foraging substrate, diet, nest site; relative mobility; geographical distributions) were affected similarly. We detected virtually no bird breeding in the latest survey periods. Eucalypt flowering has declined significantly over the past 12 years of drought.Main conclusions Declines in the largest woodland remnants commensurate with those in cleared landscapes suggest that reserve systems may not be relied upon to sustain species under climate change. We attribute population declines to low breeding success due to reduced food. Resilience of bird populations in this woodland system might be increased by active management to enhance habitat quality in existing vegetation and restoration of woodland in the more fertile parts of landscapes.

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Section: Discussionmentioning

confidence: 99%

Collapse of an avifauna: climate change appears to exacerbate habitat loss and degradation

Nally

Bennett

Thomson

et al. 2009

Diversity and Distributions

168

197

View full text Add to dashboard Cite

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“…Abundances were greatest during winter and spring when temperatures were moderate and moisture levels high, and on plots with high foliar and soil nutrient levels. Canopy arthropod abundances decline with drought (Bell 1985), as do soil and litter invertebrates (Taylor 2008). Can9PY arthropods include sap-sucking insects that produce lerp and honeydew, which are the principal foods for pardalotes, some thornbills (Acanthiza), Weebill, and short-billed honeyeaters (Uchenostomus, Melithreptus) in the GWW (Recher 1989;Recher and Davis unpubl.).…”

Section: Rainfall and Birdsmentioning

confidence: 99%

Response of birds to episodic summer rainfall in the Great Western Woodlands, Western Australia

Recher¹,

Davis²

2014

Australian Zoologist

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From 1999 to 2003. the Great Western Woodlands in Western Australia experienced above average summer and autumn rainfall. Although rainfall from 2004 to 20 I 0 approximated long-term seasonal and annual averages. the soil and litter layer became parched. there was less vegetative growth. and nectar production deciined.As habitats became drier; fewer birds nested. although some bred and fledged young. Ground. shrub. and canopy foragers. including migrants. along with nectar-feeders declined in abundance. The numbers of raptors and cuckoos declined in line with declines in abundances of prey and host species. Declines in abundance and breeding were probably linked to declines in food resources. although there were no consistent changes in the foraging behaviour of birds. There was a modest recovery in breeding effort and species abundances in 20 I 0 following above average rainfall in the spring and summer of 2008/2009.These observations indicate that productivity and avian abundance in these semiarid woodlands (200 -300 mm annual rain) decline with average rainfall. Episodes of high and possibly prolonged rainfall are required to restore productivity and allow faunal populations to recover.Climate change models predict less rain and higher temperatures in southwestern Australia. High rainfall events will occur; but there will be longer intervals of average or below average rainfall. As shown by events in 20 I O. birds can respond quickly to increased rainfall. but with longer periods of drier or even average rainfall numbers may fall to levels below which recovery is not possible. Populations in less productive habitats will disappear and the distribution of species will become increasingly patchy. with increased likelihood of local extinction.To reduce these heightened risks associated with anthropogenic climate change habitat connectivity must be maintained on regional and continental scales not presently provided by existing conservation reserves.

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“…Variables were grouped into five categories of interest, each of which could be related to arthropod biomass: ground cover (Bromham et al 1999); vegetation structure (García et al 2011); landscape structure (Burke & Nol 1998); short-term weather (Levings & Windsor 1984); and longer-term seasonal effects (Bell 1985).…”

Section: Statistical Analysesmentioning

confidence: 99%

“…Rather, short-term asynchrony at critical times may be enough to impact population fitness (Visser et al 2006;Williams & Middleton 2008;Maron et al 2015). Our sampling regime was not extensive enough to identify peaks and troughs in prey availability across seasons and years (Bell 1985;Taylor 2008), and how these fluctuations were associated with times of high energy demand.…”

Section: Prey Accessibility and Temporal Fluctuationsmentioning

confidence: 99%

Why are woodland-dependent avian insectivore populations vulnerable to declines in highly-modified landscapes?

Cosgrove¹

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Habitat loss, fragmentation, and degradation are the leading causes of faunal population declines.Substantial effort has been invested in identifying how these landscape changes are related to population parameters. However, to effectively mitigate declines, we must understand the underlying mechanisms impacted by landscape change. Woodland-dependent avian insectivores seem particularly vulnerable, and decline at rates disproportionately greater than other foraging guilds. This pattern suggests that reduced food availability in less-wooded landscapes may be a contributing factor. However, the evidence supporting this hypothesis is sparse. I adopted a multidisciplinary approach to investigate the mechanisms driving population changes of an avian insectivore in highly-modified landscapes by integrating physiological indices with measures of prey availability and landscape structure. First, I presented a framework for conceptualising how the spatiotemporal scale of fragmentation influences the mechanisms impacting populations. I then used the eastern yellow robin (Eopsaltria australis) in the Brigalow Belt South bioregion of southern Queensland to test the importance of local and landscape factors on robin site occupancy, prey density, and robin condition. I also investigated whether an index of chronic stress could be used to predict changes to robin occurrence and identify potential threats to the population. I concluded this work by conducting a supplementary feeding experiment to determine whether food availability was causing the variation in robin condition. A pilot study conducted in the study region four years earlier found that robins were more physiologically stressed (had higher heterophil:lymphocyte ratios) in sites with less woodland in the surrounding landscape, but site occupancy was unrelated to woodland cover. Re-examining the same study system, I established that woodland cover was now the strongest predictor of iii occupancy. While woodland cover at a local scale (within 500 m) was important for robin persistence, woodland cover at a broader scale relevant to dispersal movements (within 5 km) was not. While my stress index could not accurately predict the precise locations of future extirpations, patterns of stress indices (birds were more stressed where woodland cover was lower) did foreshadow a change to the pattern of occurrence. Extirpations from sites with low levels of woodland cover were balanced by colonisations of more-wooded sites. Surprisingly, I found that arthropod prey density was greater at sites that had less surrounding woodland. This result was primarily driven by a large number of Formicidae (ants). However, Formicidae have low nutritional value and once they were excluded from the results, soil moisture, not woodland cover, became the primary determinant of arthropod density. I predicted that robin condition would be strongly associated with arthropod density, but this was not the case. Instead, robins had elevated stress levels at sites with apparently more-favourable...

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Seasonal variation and the effects of drought on the abundance of arthropods in savanna woodland on the Northern Tablelands of New South Wales

Cited by 43 publications

References 9 publications

Collapse of an avifauna: climate change appears to exacerbate habitat loss and degradation

Collapse of an avifauna: climate change appears to exacerbate habitat loss and degradation

Response of birds to episodic summer rainfall in the Great Western Woodlands, Western Australia

Why are woodland-dependent avian insectivore populations vulnerable to declines in highly-modified landscapes?

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