G. C. Perkins

Changes in the avifauna of Cape York Peninsula over a period of 9 years: the relative effects of fire, vegetation type and climate

Abstract An essential component of conservation science is repeated surveys over time to monitor species that might be responding to local factors, such as land management, or more broadly to global change. A systematic survey of the avifauna of Cape York Peninsula was conducted in the late 1990s and early 2000s providing an ideal basal dataset for measuring change in the avifauna. A subset (n > 600) of these sites, primarily within savanna landscapes, was selected for re-survey in 2008 to investigate changes in bird communities on Cape York Peninsula. Changes in mean species richness varied across the study area (decreases in 59 grid cells and increases in 43) with no apparent pattern. Significant change in reporting rates was recorded in 30 species. Four sedentary and highly detectable species declined (Bar-shouldered Dove, Brown Treecreeper, Sulphur-crested Cockatoo and Pale-headed Rosella) and five increased (Peaceful Dove, Pheasant Coucal, Weebill, White-throated Honeyeater and Yellow Oriole). Habitat preference for the species that showed change remained relatively stable between the two survey periods. Some species that were recorded in very low numbers in the original survey and are considered to be threatened (Brown Treecreeper, Black-faced Woodswallow) remained in very low numbers or decreased in our survey suggesting that there has been no regional recovery of these species. Long-term monitoring can describe important patterns of species change over time, though in the case of large, highly seasonal environments like the tropical savannas, signals of change may manifest over decades rather than annually.

A bird survey method for Australian tropical savannas

Abstract The tropical savanna of northern Australia is extensive and relatively homogenous compared to the open woodlands of temperate Australia. The avifauna of this biome is unevenly dispersed in the landscape. A standard count method for birds using a timed search along a 100-m transect with eight repeated counts per site over 4 days, has been used extensively over the past decade or more in these savannas, but its effectiveness has never been critically examined. We used data collected from across northern Queensland from 2004 to 2010, comprising 502 single-survey sites (each transect counted eight times) and 60 sites re-sampled four times from 2004 to 2008, to examine species records and accumulation of species over time with respect to time of day, increasing number of repeat counts(from 2 to 32 counts), species turnover, vegetation density effects and distance to first observation. Over 70% of the species in tropical savannas were easily observed and for 93% of the species vegetation structure did not alter detectability. Richness and abundance did not vary significantly across the day. We found that repeated sampling over multiple days, and at different times of the day, provides the best estimate of species richness at a site, and improved detectability.

Signals of change in tropical savanna woodland vertebrate fauna 5 years after cessation of livestock grazing

Abstract Context. There is growing evidence that vertebrates inhabiting the extensive savannas of northern Australia are undergoing a widespread decline as a result of the effects of anthropogenic land management such as the grazing of domestic stock. Despite the ubiquity of pastoral grazing in the Australian savannas, few studies have examined the changes in terrestrial vertebrate fauna following destocking. Aims. The present study monitored the response of birds, mammals and reptiles to destocking of a newly acquired conservation reserve in north-eastern Australia. Methods. The vertebrate fauna was sampled over a 5-year period. Standardised 1-ha survey was conducted twice a year in 2006, 2007 and 2010, at 40 sites representing six habitat types. Key results. The fauna assemblage, the abundance and richness of major taxa, and the abundance of a suite of individual species were found to vary significantly with time since destocking. Although some of the observed trends were consistent with previously reported responses of vertebrates to grazing, in general species richness and abundance did not increase linearly over time since destocking, with an overall decline in the first year, and an increase in the subsequent survey. Mammals remained at very low abundance and displayed a trend contrary to that for birds and reptiles, and variation was often confounded by habitat type. Conclusions. In general, where there has been a long history of pastoral land management, destocking alone may not induce short-term increases in the vertebrate fauna thought to be affected by grazing in Australian savannas. Implications. Monitoring the outcomes of conservation management activity is a critical component of understanding the success, failures and adaptation needed to maximise the costs and benefits of conservation investment. The recovery of the vertebrate fauna thought to be of conservation concern in relatively intensively used, long-grazed landscapes may be lengthy and contingent on other factors, such as periods of favourable weather, or understanding the interactive effects of herbivore removal, fire pattern and feral predators. In such landscapes, it is possible that recovery of some elements of the vertebrate fauna may not occur without deliberate interventions, such as reintroductions or intense predator control.

Temporal variation in a savanna bird assemblage: what changes over 5 years?

Abstract Tropical savanna environments are characterised by annual and decadal patterns of resource change, which can affect the patterning of mobile fauna such as birds. In this study, we sampled 60 sites in northern Queensland, four times from 2004 to 2008. We investigated how the bird richness and abundance, and species turnover changed over the sample years and how this differed with vegetation structure. The mean abundance per site was highest in and lowest in 2008 (46.6 ± 3.3), whereas species richness per site was highest in again in 2008 (14.7 ± 0.8). Nine species were most abundant in 2004 coincident with extremely high rainfall preceding the survey in that year. Species turnover increased across all sites from 2004 to 2008 and the abundance of 13 species was best accounted for by differences in vegetation structure. Our study demonstrates that local bird communities in the semi-arid fringe of savannas can change rapidly, and mostly where vegetation is modified. This suggests that increased land-use and climate change in northern Australia could have significant effects on the avifauna over fairly short periods.

The composition of mixed-species bird flocks in northern Australian savannas

Abstract The study of the ecology of species assemblages provides information on the function and resilience of ecosystems and helps predict the response of species to environmental change. Mixed-species flocks are a particular mode of avian assemblage and are suggested to have benefits for foraging and predator vigilance. In this study we examine for the first time the composition of mixed-species flocks in Australian savannas using data from 335 mixed-species flocks recorded across northern Queensland. A total of 122 species, both passerines and non-passerines, were observed in flocks. Individual flocks comprised 2–21 species and 2–237 individuals, with small, insectivorous birds dominant. Although flock composition was largely undifferentiated, six broad groups of mixed-species flocks were identified, their similarity driven by a few key species. Our study found that mixed-species flocks are a common component of the tropical savannas and are similar in individual bird abundance and richness compared with studies in other biomes. One important next step is to examine the relationship of mixed flocks to the entire species pool, and their ecological significance within tropical savannas.

Evaluating the costs and sampling adequacy of a vertebrate monitoring program

Ecological monitoring is important for tracking trends in species and ecosystems over time and is the basis of conservation planning and government policy. Given there are increasing constraints on funding opportunities for conservation research there need to be simple approaches to assess the costs and effectiveness of surveys that highlight where methods can be refocussed to address changing management aims. In this study we use data from a vertebrate fauna monitoring program to assess the extent to which the sampling has been effective in recording the total estimated vertebrate species richness, identify which classes, families or functional groups of birds, mammals and reptiles have been under sampled by existing methods and which of the survey methods used were most cost effective. We compiled data collected over six surveys conducted over five years on a conservation reserve in northern Australia as a case study. We used rarefaction curves to examine the rate of species accumulation and sampling adequacy for 15 fauna functional groups representing bird, mammal and reptile taxa. We also compared the cost effectiveness using the relative dollar cost for six survey methods including both observational (active search, bird counts) and trapping (cage, box, funnel and pitfall traps) techniques. In our case study, despite six repeated surveys, with a total estimated cost in excess of

A significant range extension for the northern Australian gecko Strophurus taeniatus

500 000, sampling for six of the 15 targeted fauna groups was insufficient. Multiple survey methods are required to sample taxa such as reptiles and small mammals. Costs per methods were approximately equal when comparing different techniques such as pitfall, cage, Elliott and funnel traps. This study demonstrates that it is straightforward to use simple metrics of survey success to guide, refine and improve monitoring programs.

Focus on poleward shifts in species' distribution underestimates the fingerprint of climate change

The distribution and habitat associations of many northern Australian fauna are still poorly known. Predicted distributions in field guides often rely on museum collections coupled with an assessment of biogeographic and bioregional affiliations (Wilson 2005). In north-eastern Queensland, regions such as the Gulf Plains and Mitchell Grass Downs are thought to be significant barriers between eastern and western fauna species and subspecies (Schodde and Mason 1999). However there is a steady smattering of records of arid and inland species occurring much further east than anticipated (Kutt 2003). In this short note we report another bridging of this Mitchell Grass/Gulf Plain divide; in this case the known range of the gecko Strophurus taeniatus is extended east by 360 km into the edge of the Einasleigh Uplands bioregion.