scholarly journals Optimising tropical forest bird surveys using passive acoustic monitoring and repeated short-duration point counts

2020 ◽  
Author(s):  
Oliver C. Metcalf ◽  
Jos Barlow ◽  
Stuart Marsden ◽  
Nárgila Gomes de Moura ◽  
Erika Berenguer ◽  
...  
Keyword(s):  
Tropical Forests ◽  
Short Duration ◽  
Survey Methods ◽  
Alpha Diversity ◽  
Gamma Diversity ◽  
Point Count ◽  
Point Counts ◽  
Detection Frequency ◽  
Standard Duration ◽  
Avian Biodiversity

AbstractEstimation of avian biodiversity is a cornerstone measure of ecosystem condition, with turnover in avian community composition underpinning many studies of land-use change in tropical forests. Surveys conducted using autonomous recorders have been frequently found to be more efficient than traditional point-count surveys. However, there has been limited research into optimal survey duration, despite autonomous recordings allowing for many more repeats of short-duration surveys with relative ease in comparison to traditional survey methods.We use an acoustic dataset collected from a region of very high avian biodiversity - the eastern Brazilian Amazon - to test the effect of using short-duration surveys to increase temporal coverage without increasing total survey duration. We use this dataset to assess whether a survey protocol consisting of 240 15-second surveys at 29 locations, ‘short-duration surveys’, has an influence on resulting alpha and gamma diversity, and detection frequency, than ‘standard-duration surveys’ of four 15-minute surveys per location.We find that repeated short-duration surveys outperform longer duration surveys in every metric considered herein, with short-duration surveys predicted to detect approximately 50% higher alpha diversity, and 10% higher gamma diversity. Short-duration surveys also detect species more often, at more survey locations. Conversely, standard-duration surveys are almost four times more likely to produce false negatives (i.e. to fail to detect species presence). Whilst there is no difference between the proportion of uncommon species detected by the two methods, when considering species detected multiple times at multiple locations, short-duration surveys detected three times more uncommon species than standard-duration surveys.We conclude that short-duration recorded surveys should be considered the primary method for sampling the species richness of bird communities in tropical forests and is likely to be preferable to longer duration or traditional surveys in most environments.

scholarly journals Comparisons of Line Transect and Point Count Survey Methods by Estimating Density of Grey Squirrel Sciurus Carolinensis

2016 ◽  
Vol 7 (1) ◽  
pp. 17 ◽  
Author(s):  
Mariwan Rahim
Keyword(s):  
Survey Methods ◽  
Line Transect ◽  
Sciurus Carolinensis ◽  
Animal Population ◽  
Grey Squirrel ◽  
Density Estimates ◽  
East Anglia ◽  
Point Count ◽  
Point Counts ◽  
Count Surveys

<p>The methods have used to study animal population must be defined clearly at the beginning of the project. We compared line transect and point count survey methods to estimating the density of grey squirrel at University of East Anglia campus (UEA), Norwich-United Kingdom. Across the entire UEA campus we surveyed 0.43698 ha of the 146 ha of the campus area. A total of 21 squirrels were observed during survey between 21<sup>st</sup>-26<sup>th</sup> in December 2013. Nine individuals were observed during line transect and twelve individuals were observed during point counts. The average number of species detected was differing between the two methods. Density estimates of grey squirrel from the two methods were different. Densities of grey squirrel as estimated by point count surveys were higher than those by line transect count surveys. Our results indicate that it is important to account for different survey methods when comparing the two methods to estimate the grey squirrel.</p>

scholarly journals Comparison of point and roadside transect methods to evaluate the abundance and richness of diurnal raptors in the arid region of Rajasthan

PLoS ONE ◽  
2021 ◽  
Vol 16 (12) ◽  
pp. e0259805
Author(s):  
Govind Tiwari ◽  
Puneet Pandey ◽  
Rahul Kaul ◽  
Hang Lee ◽  
Randeep Singh
Keyword(s):  
Species Richness ◽  
Average Length ◽  
Survey Methods ◽  
Survey Method ◽  
Point Count ◽  
Point Counts ◽  
Significant Difference ◽  
Unidentified Species ◽  
Species Richness And Abundance ◽  
Point Count Method

Diurnal raptors show a wider distribution compared to other groups of birds including passerines, woodpeckers, and seriemas, but occur at lower-than-expected densities. Estimating the precise abundance is essential to achieve conservation goals but the methods used to estimate the populations of birds need to be appropriate to arrive at meaningful conclusions. We compared the two survey methods: roadside point count and strip transects, for estimating species richness and abundance of raptors in the arid landscape of Rajasthan. Roadside point counts and roadside strip transects were done on 50 transects between December 2019- February 2020 (with an average length of 20 km and a total distance of 3000 km) to assess the species richness and abundance of raptors. A total of 2954 observations of raptors belonging to 35 species were recorded using both methods. Mann Whitney U test result showed no significant difference in species richness and abundance estimates between both methods (p = 0.206). The point count method yielded a higher relative abundance of 2.79 individuals [10 km2]-1h-1 than the 1.90 individuals [10 km2]-1h-1 obtained during the strip transect. Also, the number of unidentified species were less for point counts. Extrapolation values indicated that both the methods do not differ much for the detection of unsampled species. The choice of survey method depends on the objectives of the study, but our results favor the use of point counts rather than strip transects to survey raptors in open habitats. The information generated from this study is expected to provide the most efficient method to study the abundance and distribution of raptors in similar landscapes.

scholarly journals On the use of 10-minute point counts and 10-species lists for surveying birds in lowland Atlantic Forests in southeastern Brazil

2012 ◽  
Vol 52 (28) ◽  
pp. 333-340 ◽  
Author(s):  
Vagner Cavarzere ◽  
Thiago Vernaschi Vieira da Costa ◽  
Luís Fábio Silveira
Keyword(s):  
Rapid Assessment ◽  
Southeastern Brazil ◽  
Point Counting ◽  
Point Count ◽  
Point Counts ◽  
Time Period ◽  
Minute Point ◽  
Species Lists ◽  
Point Count Method ◽  
Breeding Seasons

Due to rapid and continuous deforestation, recent bird surveys in the Atlantic Forest are following rapid assessment programs to accumulate significant amounts of data during short periods of time. During this study, two surveying methods were used to evaluate which technique rapidly accumulated most species (> 90% of the estimated empirical value) at lowland Atlantic Forests in the state of São Paulo, southeastern Brazil. Birds were counted during the 2008-2010 breeding seasons using 10-minute point counts and 10-species lists. Overall, point counting detected as many species as lists (79 vs. 83, respectively), and 88 points (14.7 h) detected 90% of the estimated species richness. Forty-one lists were insufficient to detect 90% of all species. However, lists accumulated species faster in a shorter time period, probably due to the nature of the point count method in which species detected while moving between points are not considered. Rapid assessment programs in these forests will rapidly detect more species using 10-species lists. Both methods shared 63% of all forest species, but this may be due to spatial and temporal mismatch between samplings of each method.

Problems with Avian Point Counts for Estimating Density of Northern Bobwhite—A Case Study

2011 ◽  
Vol 2 (1) ◽  
pp. 117-121 ◽  
Author(s):  
Roger D. Applegate ◽  
Robert E. Kissell ◽  
E. Daniel Moss ◽  
Edward L. Warr ◽  
Michael L. Kennedy
Keyword(s):  
Count Data ◽  
Distance Sampling ◽  
Bird Species ◽  
Northern Bobwhite ◽  
Model Fit ◽  
Point Count ◽  
Point Counts ◽  
Occupancy Estimation ◽  
Detection Probabilities

Abstract Point count data are used increasingly to provide density estimates of bird species. A favored approach to analyze point count data uses distance sampling theory where model selection and model fit are important considerations. We used uniform and half normal models and assessed model fit using χ2 analysis. We were unsuccessful in fitting models to 635 northern bobwhite Colinus virginianus observations from 85 avian point locations spanning 6 y (P ≤ 0.05). Most observations (74%) occurred in the outermost (&gt;100-m) distance radius. Our results violated the assumptions that all observations at the point are detected. The assumption that birds were assigned to the correct distance interval also was probably violated. We caution managers in implementing avian point counts with distance sampling when estimating northern bobwhite population density. We recommend exploring other approaches such as occupancy-estimation and modeling for estimating detection probabilities.

scholarly journals Singing in the suburbs: point count surveys efficiently reveal habitat associations for nocturnal Orthoptera across an urban-to-rural gradient

2020 ◽  
Vol 24 (6) ◽  
pp. 1031-1043
Author(s):  
Darin J. McNeil ◽  
Christina M. Grozinger
Keyword(s):  
Site Occupancy ◽  
Habitat Associations ◽  
Survey Method ◽  
Population Declines ◽  
Detection Rates ◽  
Point Count ◽  
Point Counts ◽  
Focal Species ◽  
Habitat Gradient ◽  
Count Surveys

Abstract As evidence for global insect population declines continues to amass, several studies have indicated that Orthoptera (grasshoppers, crickets, and katydids) are among the most threatened insect groups. Understanding Orthoptera populations across large spatial extents requires efficient survey protocols, however, many previously established methods are expensive and/or labor-intensive. One survey method widely employed in wildlife biology, the aural point count, may work well for crickets and katydids (suborder: Ensifera) because males produce conspicuous, species-specific mating calls. We conducted repeated point count surveys across an urban-to-rural gradient in central Pennsylvania. Occupancy analyses of ten focal species indicated that, although detection probability rates varied by species from 0.43 to 0.98, detection rates compounded over five visits such that all focal species achieved cumulative > 0.90. Factors associated with site occupancy varied among species with some positively associated with urbanization (e.g., Greater Anglewing, Microcentrum rhombifolium), some negatively associated with urbanization (e.g., Sword-bearing Conehead, Neoconocephalus ensiger), and others exhibiting constant occupancy across a habitat gradient (e.g., Common True Katydid, Pterophylla camellifolia). Our community-level analysis revealed that different species’ habitat associations interacted such that intermediate levels of urbanization (i.e., suburbs) hosted the highest number of species. Implications for insect conservation Ultimately, our analyses clearly support the concept that aural point counts paired with static occupancy modeling can serve as an important tool for monitoring night-singing Orthoptera populations. Applications of point count surveys by both researchers and citizen scientists may improve our understanding Ensifera populations and help in the global conservation of these threatened insects.

scholarly journals Incorporating Availability for Detection in Estimates of Bird Abundance

The Auk ◽  
2007 ◽  
Vol 124 (1) ◽  
pp. 96-106 ◽  
Author(s):  
Duane R. Diefenbach ◽  
Matthew R. Marshall ◽  
Jennifer A. Mattice ◽  
Daniel W. Brauning
Keyword(s):  
Survey Methods ◽  
Distance Sampling ◽  
Sampling Period ◽  
Bird Abundance ◽  
Point Counts ◽  
Variance Estimators ◽  
Bird Survey ◽  
Detection Probabilities ◽  
Ammodramus Henslowii ◽  
Further Development

Abstract Several bird-survey methods have been proposed that provide an estimated detection probability so that bird-count statistics can be used to estimate bird abundance. However, some of these estimators adjust counts of birds observed by the probability that a bird is detected and assume that all birds are available to be detected at the time of the survey. We marked male Henslow's Sparrows (Ammodramus henslowii) and Grasshopper Sparrows (A. savannarum) and monitored their behavior during May-July 2002 and 2003 to estimate the proportion of time they were available for detection. We found that the availability of Henslow's Sparrows declined in late June to <10% for 5- or 10-min point counts when a male had to sing and be visible to the observer; but during 20 May-19 June, males were available for detection 39.1% (SD = 27.3) of the time for 5-min point counts and 43.9% (SD = 28.9) of the time for 10-min point counts (n = 54). We detected no temporal changes in availability for Grasshopper Sparrows, but estimated availability to be much lower for 5-min point counts (10.3%, SD = 12.2) than for 10-min point counts (19.2%, SD = 22.3) when males had to be visible and sing during the sampling period (n = 80). For distance sampling, we estimated the availability of Henslow's Sparrows to be 44.2% (SD = 29.0) and the availability of Grasshopper Sparrows to be 20.6% (SD = 23.5). We show how our estimates of availability can be incorporated in the abundance and variance estimators for distance sampling and modify the abundance and variance estimators for the double-observer method. Methods that directly estimate availability from bird counts but also incorporate detection probabilities need further development and will be important for obtaining unbiased estimates of abundance for these species. Incorporación de la Disponibilidad para la Detección en las Estimaciones de Abundancia de Aves

scholarly journals Estimating Detection Probability and Density from Point-Count Surveys: A Combination of Distance and Double-Observer Sampling

The Auk ◽  
2006 ◽  
Vol 123 (3) ◽  
pp. 735-752 ◽  
Author(s):  
Michelle L. Kissling ◽  
Edward O. Garton
Keyword(s):  
Detection Probability ◽  
Survey Methods ◽  
Effective Area ◽  
Survey Method ◽  
Density Estimates ◽  
Point Count ◽  
Detection Probabilities ◽  
Fixed Radius ◽  
Count Surveys ◽  
Double Observer

Abstract Point counts are the method most commonly used to estimate abundance of birds, but they often fail to account properly for incomplete and variable detection probabilities. We developed a technique that combines distance and double-observer sampling to estimate detection probabilities and effective area surveyed. We applied this paired-observer, variable circular-plot (POVCP) technique to point-count surveys (n = 753) conducted in closed-canopy forests of southeast Alaska. Distance data were analyzed for each species to model a detection probability for each observer and calculate an estimate of density. We then multiplied each observer's density estimates by a correction factor to adjust for detection probabilities <1 at plot center. We compared analytical results from four survey methods: single-observer fixed-radius (50-m) plot; single-observer, variable circular-plot (SOVCP); double-observer fixed-radius (50-m) plot; and POVCP. We examined differences in detection probabilities at plot center, effective area surveyed, and densities for five bird species: Pacific-slope Flycatcher (Empidonax difficilis), Winter Wren (Troglodytes troglodytes), Golden-crowned Kinglet (Regulus satrapa), Hermit Thrush (Catharus guttatus), and Townsend's Warbler (Dendroica townsendi). Average detection probabilities for paired observers increased ≈8% (SE = 2.9) for all species once estimates were corrected for birds missed at plot center. Density estimators of fixed-radius survey methods were likely negatively biased, because the key assumption of perfect detection was not met. Density estimates generated using SOVCP and POVCP were similar, but standard errors were much lower for the POVCP survey method. We recommend using POVCP when study objectives require precise estimates of density. Failure to account for differences in detection probabilities and effective area surveyed results in biased population estimators and, therefore, faulty inferences about the population in question. Estimaciones de la Densidad y de las Probabilidades de Detección a Partir de Muestreos Utilizando Conteos en Puntos: Una Combinación de Muestreos de Distancia y de Doble Observador

scholarly journals Power to Detect Trend in Short-Term Time Series of Bird Abundance

The Condor ◽  
2007 ◽  
Vol 109 (4) ◽  
pp. 943-948
Author(s):  
Wayne E. Thogmartin ◽  
Brian R. Gray ◽  
Maureen Gallagher ◽  
Neal Young ◽  
Jason J. Rohweder ◽  
...  
Keyword(s):  
Sample Size ◽  
Short Duration ◽  
Bird Species ◽  
Population Monitoring ◽  
Short Term ◽  
Wet Prairie ◽  
Bird Abundance ◽  
Point Counts ◽  
Study Sites ◽  
Species Specific

Abstract Avian point counts for population monitoring are often collected over a short timespan (e.g., 3–5 years). We examined whether power was adequate (power ≥0.80) in short-duration studies to warrant the calculation of trend estimates. We modeled power to detect trends in abundance indices of eight bird species occurring across three floodplain habitats (wet prairie, early successional forest, and mature forest) as a function of trend magnitude, sample size, and species-specific sampling and among-year variance components. Point counts (5 min) were collected from 365 locations distributed among 10 study sites along the lower Missouri River; counts were collected over the period 2002 to 2004. For all study species, power appeared adequate to detect trends in studies of short duration (three years) at a single site when exponential declines were relatively large in magnitude (more than −5% year−1) and the sample of point counts per year was ≥30. Efforts to monitor avian trends with point counts in small managed lands (i.e., refuges and parks) should recognize this sample size restriction by including point counts from offsite locations as a means of obtaining sufficient numbers of samples per strata. Trends of less than −5% year−1 are not likely to be consistently detected for most species over the short term, but short-term monitoring may still be useful as the basis for comparisons with future surveys.

Alpha, beta, or gamma: where does all the diversity go?

Paleobiology ◽  
1988 ◽  
Vol 14 (3) ◽  
pp. 221-234 ◽  
Author(s):  
J. John Sepkoski
Keyword(s):  
Beta Diversity ◽  
Alpha Diversity ◽  
Taxonomic Richness ◽  
Soft Bottom ◽  
Gamma Diversity ◽  
Data Set ◽  
Alpha And Beta Diversity ◽  
Community Or ◽  
Global Diversity ◽  
Measured Change

Global taxonomic richness is affected by variation in three components: within-community, or alpha, diversity; between-community, or beta, diversity; and between-region, or gamma, diversity. A data set consisting of 505 faunal lists distributed among 40 stratigraphic intervals and six environmental zones was used to investigate how variation in alpha and beta diversity influenced global diversity through the Paleozoic, and especially during the Ordovician radiations. As first shown by Bambach (1977), alpha diversity increased by 50 to 70 percent in offshore marine environments during the Ordovician and then remained essentially constant for the remainder of the Paleozoic. The increase is insufficient, however, to account for the 300 percent rise observed in global generic diversity. It is shown that beta diversity among level, soft-bottom communities also increased significantly during the early Paleozoic. This change is related to enhanced habitat selection, and presumably increased overall specialization, among diversifying taxa during the Ordovician radiations. Combined with alpha diversity, the measured change in beta diversity still accounts for only about half of the increase in global diversity. Other sources of increase are probably not related to variation in gamma diversity but rather to appearance and/or expansion of organic reefs, hardground communities, bryozoan thickets, and crinoid gardens during the Ordovician.

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