scholarly journals Comparison of Surveys of Kangaroos in Queensland Using Helicopters and Fixed-Wing Aircraft.

1998 ◽  
Vol 20 (1) ◽  
pp. 92 ◽  
Author(s):  
AR Pople ◽  
SC Cairns ◽  
TF Clancy ◽  
GC Grigg ◽  
LA Beard ◽  
...  
Keyword(s):  
Aerial Survey ◽  
Population Estimates ◽  
Line Transect ◽  
Correction Factors ◽  
Density Estimates ◽  
Australian State ◽  
Transect Counts ◽  
Comparative Accuracy ◽  
Harvest Quotas ◽  
Strip Transect

Kangaroo harvest quotas for each Australian state have been set mainly as proportions of population estimates derived from aerial surveys. Estimating population size from strip transect counts using fixed- wing aircraft has become an established technique, but counts must be adjusted by correction factors to ensure population estimates are both accurate and repeatable. Surveys of kangaroos in Queensland are currently conducted with helicopters using line transect methodology, but cost restricts their use to relatively small survey blocks. Nevertheless, they return more accurate and repeatable estimates of kangaroo density than surveys with fixed-wing aircraft. A comparison of the above two techniques was made along the same transect lines in seven survey blocks (5000-10,000 km2) in southern and western Queensland, allowing an assessment of the comparative accuracy of the fixed-wing method. For red kangaroos (Macropus rufus), required correction factors of 0.7-3.1 were similar to those used previously. However, for eastern grey kangaroos (M. giganteus), substantially larger correction factors of 3.4-10.2 were needed to approach true density. For wallaroos (M. robustus), correction factors of 3.8-4.8 were required, but can be considered conservative because helicopter-derived density estimates are known to be underestimated by a factor of 2-3. Further work is needed to establish how correction factors for each species should be applied on a broader scale and whether they lead to repeatable estimates of kangaroo density. Key words: aerial survey, line transect, correction factors, strip transect, wallaroo.

scholarly journals An assessment of the accuracy of kangaroo surveys using fixed-wing aircraft

1998 ◽  
Vol 25 (3) ◽  
pp. 315 ◽  
Author(s):  
A. R. Pople ◽  
S. C. Cairns ◽  
T. F. Clancy ◽  
G. C. Grigg ◽  
L. A. Beard ◽  
...  
Keyword(s):  
Standard Form ◽  
Cost Effective ◽  
Line Transect ◽  
Attractive Alternative ◽  
Correction Factors ◽  
Density Estimates ◽  
Macropus Rufus ◽  
Transect Counts ◽  
Biased Estimates ◽  
Strip Transect

The use of line-transect methodology, on foot or from a helicopter, is likely to return the most repeatable, least biased estimates of kangaroo density. However, the associated costs make both methods impractical for broad-scale surveys. For these, a fixed-wing aircraft remains the most cost-effective platform. Limitations of the standard fixed-wing method (200-m strip transects) are well known, but it continues to be used because it provides an index of trends, because there are now long runs of data (almost 20 years in some cases) collected in this standard form and an alternative method is lacking. In this study, four variations of fixed-wing surveys of kangaroos were investigated: two line-transect methods (involving different scanning techniques), the standard 200-m strip transect and a 100-m strip transect. Surveys using these methods were compared with helicopter line-transect surveys along the same flight lines in three areas (5000–7500 km2) in western Queensland. Both fixed-wing line-transect methods failed to produce consistently accurate estimates of density for all three species surveyed: red kangaroos (Macropus rufus), eastern grey kangaroos (M. giganteus) and common wallaroos (M. robustus). While generally more accurate than the uncorrected strip-transect counts, they were no less variable. However, the strip-transect counts still need to be corrected for bias for which this study offers revised estimates of correction factors for eastern grey kangaroos (3.7–10.2) and common wallaroos (3.8–4.1), and estimates for red kangaroos (1.7–2.7) that support currently used values. An attractive alternative is to survey in 100-m strip transects, which offer improved visibility (correction factors of 1.0–1.8 for red kangaroos, 2.1–3.6 for eastern grey kangaroos and 1.7–2.1 for common wallaroos) and are therefore likely to be more accurate and repeatable. However, these advantages need to be assessed in relation to continuing long runs of data using the standard 200-m strip transect. Correction factors for wallaroos are conservative as helicopter-based density estimates are known to be underestimates. Further work is needed to assess the generality of correction factors, both spatially and temporally.

A Test of the Accuracy of Line and Strip Transect Estimators in Aerial Survey

1988 ◽  
Vol 15 (5) ◽  
pp. 493 ◽  
Author(s):  
J Hone
Keyword(s):  
Fourier Series ◽  
Hermite Polynomial ◽  
Aerial Survey ◽  
Survey Method ◽  
Line Transect ◽  
Accuracy And Precision ◽  
Exponential Power ◽  
Negative Exponential ◽  
Similar Accuracy ◽  
Strip Transect

The accuracy and precision of eight line transect estimators and one strip transect estimator were examined by helicopter aerial survey. Carcasses of feral pigs were counted in an area of treeless floodplain and Eucalyptus woodland. The ratio and Cox's methods, Fourier series, exponential power series, half-normal, exponential polynomial, negative exponential, hermite polynomial and hazard rate estimators gave accurate estimates. Using the survey method described, most estimators were of similar accuracy and precision, but the Fourier series estimator was the most accurate.

An Evaluation of the Strip Transect Method for Censusing Bird Communities in Forests

1986 ◽  
Vol 13 (2) ◽  
pp. 203 ◽  
Author(s):  
RH Harden ◽  
RJ Muir ◽  
DR Milledge
Keyword(s):  
New South ◽  
Bird Communities ◽  
Density Estimate ◽  
Density Estimates ◽  
Number Of Species ◽  
South Wales ◽  
Sclerophyll Forest ◽  
Transect Counts ◽  
Estimate Number ◽  
Strip Transect

The effects of varying transect width and census duration on the number of birds counted, the density estimate, number of species detected and the percentage of unidentified birds were examined in rainforest and wet sclerophyll forest at Mount Nardi in northern New South Wales. The nine combinations of three strip widths (40, 60 and 80 m) and three durations of census (24, 18 and 12 min) were compared in 200-m-long transects in each forest. The census of birds was more sensitive to changes in census duration than in strip width, and the effects were greater in the rainforest than the wet sclerophyll forest. Both the precision of the density estimates and the number of species detected were highest for the narrowest strips censused for the longest time. The bias of the density estimate varied with the treatments both within and between forests, and thus the strip transect could not be used to compare them. We suggest that variation in bias between sites may be a problem common to all transect counts of birds.

scholarly journals Group IV humpback whales: their status from aerial and landbased surveys off Western Australia, 2005

2020 ◽  
pp. 223-234
Author(s):  
Charles G.M. Paxton ◽  
Sharon l. Hedley ◽  
John l. Bannister
Keyword(s):  
Aerial Survey ◽  
Group Iv ◽  
Humpback Whales ◽  
Reliable Estimate ◽  
Line Transect ◽  
Absolute Abundance ◽  
Density Estimates ◽  
Abundance Estimates ◽  
Short Period ◽  
Land Station

Single platform aerial line transect and land-based surveys of Southern Hemisphere Group IV humpback whales were undertaken to provide absoluteabundance estimates of animals migrating northward along the western Australian coast during June–August 2005. The aerial survey was designedto cover the whole period of northward migration but the resulting estimates from that survey alone could only, at best, provide relative abundanceestimates as it was not possible to estimate g(0), the detection probability along the trackline, from the data. Owing to logistical constraints, theland-based survey was only possible for a much shorter period (two weeks during the expected peak of the migration in mid-July). This paperproposes three methods that utilise these complementary data in different ways to attempt to obtain absolute abundance estimates. The aerial linetransect data were used to estimate relative whale density (for each day), allowing absolute abundance from the land-based survey to be estimatedfor the short period of its duration. In turn, the land-based survey allowed estimation of g(0) for the aerial survey. Absolute estimates of abundancefor the aerial survey were obtained by combining the g(0) estimate with the relative density estimates, summing over the appropriate number ofdays. The most reliable estimate of northward migrating whales passing the land station for the period of the land-based survey only was 4,700(95% CI 2,700–14,000). The most reliable estimate for the number of whales passing through the aerial survey region for the duration of that survey(55 days from June through to August) was 10,300 (95% CI 6,700–24,500). This is a conservative estimate because the duration of the aerial surveywas almost certainly shorter than the period of the migration. Extrapolation beyond the end of this survey was considered unreliable, but abundancefrom the estimated start of the migration to the end of the survey (87 days from mid-April to August) was estimated to be 12,800 (95% CI 7,500–44,600). The estimated number of whales depends crucially on the assumed migration and period of migration. Results for different migrationparameters are also presented. The point estimates of abundance, whilst higher than those from a previous survey in 1999 (when adjusted for surveyduration) are not significantly so. The peak of the whales’ distribution was found at c.90m water depth.

Comparison of Helicopter Line Transects with Walked Line Transects for Estimating Densities of Kangaroos

1997 ◽  
Vol 24 (4) ◽  
pp. 397 ◽  
Author(s):  
T. F. Clancy ◽  
A. R. Pople ◽  
L. A. Gibson
Keyword(s):  
Repeated Measures ◽  
Aerial Survey ◽  
Survey Method ◽  
Line Transect ◽  
Attractive Alternative ◽  
Line Transect Sampling ◽  
Density Estimates ◽  
Transect Sampling ◽  
Grey Kangaroo ◽  
Line Transects

The performance of helicopter surveys for estimating population densities of red kangaroos (Macropus rufus), eastern grey kangaroos (Macropus giganteus) and common wallaroos (Macropus robustus) was investigated by comparing line-transect density estimates obtained from helicopter surveys with those from ground (walked) surveys. Comparisons were made at four sites in central western Queensland (areas with high densities of red kangaroos and common wallaroos) that were surveyed during winter and summer from December 1991 until February 1995, and one site in south-eastern Queensland (an area of high eastern grey kangaroo density) surveyed annually during autumn from March 1991 until March 1994. Helicopter surveys generally recorded lower sample sizes than did ground surveys (means ± s.e = 34 ± 6%, 33 ± 9% and 76 ± 2% lower for red kangaroos, eastern grey kangaroos and wallaroos, respectively). Density estimates obtained from the helicopter surveys were not significantly different from those obtained from ground surveys for both red and eastern grey kangaroos as assessed by repeated-measures ANOVA and regression analysis. However, helicopter surveys of common wallaroos consistently returned density estimates about half those of ground surveys. The relationships between the two methods did not differ between winter and summer for any species. The conventional aerial survey method for kangaroos of strip transects from fixed-wing aircraft has limited ability to adjust for varying sightability conditions. Therefore, helicopter surveys with line-transect sampling are an attractive alternative.

Distribution and Abundance of Feral Livestock in the 'Top End' of the Northern Territory (1985-86), and Their Relation to Population Control.

1989 ◽  
Vol 16 (6) ◽  
pp. 651 ◽  
Author(s):  
P Bayliss ◽  
P Bayliss ◽  
KM Yeomans ◽  
KM Yeomans
Keyword(s):  
Population Control ◽  
Sampling Rate ◽  
Aerial Survey ◽  
Northern Territory ◽  
Population Estimates ◽  
Correction Factors ◽  
Coastal Lowland ◽  
Domestic Livestock ◽  
The Mean ◽  
Over The Top

Feral and domestic livestock (buffalo, cattle, horses and donkeys) were censused by fixed-wing aerial survey over the 'Top End' of the Northern Territory (above the 16th parallel) in March-April 1985, encompassing 233 672 km2 (16.7% of the Territory). The mean sampling rate on the major coastal lowland (38 281 km2) was 7.3%, and that for the rest was 3.7%. The accuracy of population estimates was improved by applying habitat-specific visibility correction factors to animals counted in groups.

scholarly journals Improving population estimates of Swedish birds using the Breeding Bird Survey fixed routes and correction factors from Finnish line transect surveys

Ornis Svecica ◽  
2016 ◽  
Vol 26 (3–4) ◽  
pp. 177-190
Author(s):  
Sören Svensson
Keyword(s):  
Abundant Species ◽  
New Method ◽  
Population Estimates ◽  
Line Transect ◽  
Correction Factors ◽  
Breeding Bird ◽  
Bird Survey ◽  
Previous Account ◽  
Line Transects ◽  
Common Birds

I estimated population size of fifty-nine common birds by using the fixed routes of the Swedish Bird Survey (SBS), which give the number of birds per kilometer. I converted this number to density, birds/km2, using the correction factors for detectability that have been developed for line transects in Finland. I compared the population estimates by this new method with those in a previous account from 2012, in which the estimates of common birds were primarily based on extrapolation of habitat-specific densities from numerous territory mapping plots. There was good agreement for the most abundant species but a clear tendency that the estimates with the new method were higher for many less common ones. As little new density data are being collected, the SBS fixed routes are likely to be the prime source of data for future national population estimates. Although the Finnish correction factors can be used to improve the Swedish estimates for suitable species it is advisable to develop factors specifically adapted to the Swedish counts for application to a wider spectrum of species.

Correcting for Incomplete Sighting in Aerial Surveys of Kangaroos

1986 ◽  
Vol 13 (3) ◽  
pp. 339 ◽  
Author(s):  
A Barnes ◽  
GJE Hill ◽  
GR Wilson
Keyword(s):  
Species Differences ◽  
Aerial Survey ◽  
Time Of Day ◽  
Correction Factors ◽  
Density Estimates ◽  
Mathematical Properties ◽  
Aerial Surveys ◽  
Alternative Method ◽  
Management Procedures ◽  
Continued Use

Kangaroo density estimates derived from aerial survey depend on the method of deriving sightability correction factors developed by Caughley. The method depends on five assumptions, some concerned with the mathematical properties of a model for sightability probabilities and others with deriving correction factors from this model. All these assumptions can be criticized. In addition, evidence on the performance of the method does not suggest that it is accurate. Published density estimates are less precise than indicated, and may include biases due to factors not considered in the correction factors used, e.g. seasonal conditions, time of day, and species differences. At present, no satisfactory alternative method of correction exists but, because inaccuracies may be large, continued use of the method requires much greater caution than has previously been shown. This is particularly relevant where density estimates are used to determine management procedures.

scholarly journals Performance of manned and unmanned aerial surveys to collect visual data and imagery for estimating arctic cetacean density and associated uncertainty

2018 ◽  
Vol 6 (3) ◽  
pp. 128-154 ◽  
Author(s):  
M.C. Ferguson ◽  
R.P. Angliss ◽  
A. Kennedy ◽  
B. Lynch ◽  
A. Willoughby ◽  
...  
Keyword(s):  
Marine Mammal ◽  
Aerial Survey ◽  
Small Sample ◽  
Unmanned Aircraft ◽  
Bowhead Whale ◽  
Line Transect ◽  
Camera System ◽  
Density Estimates ◽  
Aerial Surveys ◽  
The Cost

Manned aerial surveys have been used successfully for decades to collect data to infer cetacean distribution, density (number of whales/km2), and abundance. Unmanned aircraft systems (UAS) have potential to augment or replace some manned aerial surveys for cetaceans. We conducted a three-way comparison among visual observations made by marine mammal observers aboard a Turbo Commander aircraft; imagery autonomously collected by a Nikon D810 camera system mounted to a belly port on the Turbo Commander; and imagery collected by a similar camera system on a remotely controlled ScanEagle® UAS operated by the US Navy. Bowhead whale density estimates derived from the marine mammal observer data were higher than those from the Turbo Commander imagery; comparisons to the UAS imagery depended on survey sector and analytical method. Beluga density estimates derived from either dataset collected aboard the Turbo Commander were higher than estimates derived from the UAS imagery. Uncertainties in density estimates derived from the marine mammal observer data were lower than estimates derived from either imagery dataset due to the small sample sizes in the imagery. The visual line-transect aerial survey conducted by marine mammal observers aboard the Turbo Commander was 68.5% of the cost of the photo strip-transect survey aboard the same aircraft and 9.4% of the cost of the UAS survey.

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