Response to Huso and Erickson's comments on novel scavenger removal trials

Smallwood, K. Shawn; Bell, Douglas A.; Karas, Brian; Snyder, Sara

doi:10.1002/jwmg.482

Cited by 12 publications

(14 citation statements)

References 14 publications

(33 reference statements)

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“…Whole carcasses are more likely than pieces to be picked up intact and removed at once by a single scavenger. Furthermore, calculating the proportion of carcasses remaining at pre‐defined time intervals rather than at exact times of carcass removals tends to right‐shift the data distribution, resulting in a biased representation of removal rates in the first few days after carcass placement (Smallwood et al 2013).…”

Section: Discussionmentioning

confidence: 99%

“…This approach is more efficient than using separate groups of carcasses for each trial, but it still fails to account for the increased detection rates of placed carcasses in the removal trial. A more realistic approach to quantifying the proportion of carcasses not detected by searches would be to fully integrate the trials into standard fatality monitoring: where D is the proportion of placed carcasses that is detected by searchers performing standard fatality searches throughout a given monitoring period, and d is the adjustment factor for search radius bias (also see Smallwood et al 2013). Using this approach, the investigator does not care whether carcasses were undetected due to searcher error or scavenger removal, and there is no added detection likelihood resulting from performing status checks on placed carcasses.…”

Section: Discussionmentioning

confidence: 99%

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Comparing bird and bat fatality‐rate estimates among North American wind‐energy projects

Smallwood¹

2013

Wildlife Society Bulletin

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167

179

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Estimates of bird and bat fatalities are often made at wind‐energy projects to assess impacts by comparing them with other fatality estimates. Many fatality estimates have been made across North America, but they have varied greatly in field and analytical methods, monitoring duration, and in the size and height of the wind turbines monitored for fatalities, and few benefited from scientific peer review. To improve comparability among estimates, I reviewed available reports of fatality monitoring at wind‐energy projects throughout North America, and I applied a common estimator and 3 adjustment factors to data collected from these reports. To adjust fatality estimates for proportions of carcasses not found during routine monitoring, I used national averages from hundreds of carcass placement trials intended to characterize scavenger removal and searcher detection rates, and I relied on patterns of carcass distance from wind turbines to develop an adjustment for variation in maximum search radius around wind turbines mounted on various tower heights. Adjusted fatality rates correlated inversely with wind‐turbine size for all raptors as a group across the United States, and for all birds as a group within the Altamont Pass Wind Resource Area, California. I estimated 888,000 bat and 573,000 bird fatalities/year (including 83,000 raptor fatalities) at 51,630 megawatt (MW) of installed wind‐energy capacity in the United States in 2012. As wind energy continues to expand, there is urgent need to improve fatality monitoring methods, especially in the implementation of detection trials, which should be more realistically incorporated into routine monitoring. © 2013 The Wildlife Society

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Comparing bird and bat fatality‐rate estimates among North American wind‐energy projects

Smallwood¹

2013

Wildlife Society Bulletin

Self Cite

167

179

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“…Estimators based on proportion of carcasses remaining by the end of a search interval tacitly assume that no carcasses persist beyond the search interval to be detected during a subsequent search. Estimators based on mean days to carcass removal (

\overset{\overset{t}{true}}{true}

) often assume exponential carcass persistence through the search interval ( I ):

r = e^{\frac{- I}{\overset{\overset{t}{true}}{true}}}

(Huso , Warren‐Hicks et al ), but this assumption is unrealistic for carcasses persisting >8 days because vertebrate scavengers remove fewer older carcasses (Smallwood et al ). For both types of estimators, an assumed steady rate of carcass deposition is probably unrealistic because of seasonal and annual variation in fatalities.…”

mentioning

confidence: 99%

“…As potential errors and bias emerged in discussions around fatality estimation (Smallwood ; Smallwood et al , ; Huso and Erickson ), investigators sought to rectify the problems of bias using statistical methods (Bispo et al , Huso , Korner‐Nievergelt et al , Péron et al , Huso et al ), whereas field methods remained largely unaddressed. However, if the data used for fatality estimators are poorly founded, then the estimates will be poorly founded regardless of the estimator.…”

mentioning

confidence: 99%

“…Smallwood et al () introduced field methods to improve understanding of carcass persistence, and Warren‐Hicks et al () introduced an integration of detection trials into routine monitoring. Smallwood () and Smallwood et al () suggested estimating an overall detection rate rather than separate rates of searcher detection and carcass persistence, an approach we implemented here.…”

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confidence: 99%

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Estimating wind turbine fatalities using integrated detection trials

Smallwood¹,

Bell²,

Walther³

et al. 2018

J Wildl Manag

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Fatality monitoring at wind projects requires carcass detection trials to adjust fatality estimates for the proportion of fatalities not found. However, detection trials vary greatly in metric, duration, carcass monitoring schedule, species, number placed, state of decomposition, whether placed within or outside search areas, and other factors. We introduce a new approach for estimating fatalities by quantifying overall detection rates rather than separate rates for searcher detection error and carcass persistence, and by leaving placed and found fatality carcasses undisturbed throughout monitoring. We placed 2 fresh‐frozen bird carcasses weekly at random sites within fatality search areas and on randomized days Monday–Friday at Sand Hill and Santa Clara wind projects, Altamont Pass Wind Resource Area, California, USA. To estimate detection rates, we used logit regression to fit detection outcomes on body mass, which served as an axis of similitude between placed trial carcasses and fatality finds. Adjusted carcass placement rates among species detected by searchers regressed on true placement rates with a slope of 1.0 so long as sufficient numbers of trial carcasses were placed, thus validating our approach as an unbiased estimator. Our approach generally estimated lower fatality rates than did conventional approaches, the latter of which demonstrated biases in searcher detection rates and carcass persistence rates whether based on proportion of carcasses remaining or mean days to removal. Our approach also revealed detection errors that highlight the difficulty of finding and identifying the remains of dead animals, and which warrant routine reporting. Despite averaging only a 5‐day search interval on intensively grazed annual grasslands where ground visibility was usually high, our experienced fatality monitors averaged 4.3 searches/first carcass detection, failed to detect 25% of 75 species represented by placed carcasses, and misidentified carcasses to species among 44% of species detected. Estimates of time since death also suffered bias and large error. Our approach more realistically simulates carcass detection probabilities associated with fatality monitoring, is less costly, facilitates hypothesis testing, eliminates multiple sources of error and bias suspected of conventional methods, and enables quantification of errors in estimated time since death, species identifications, and false negative findings. © 2018 The Wildlife Society.

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Dogs Detect Larger Wind Energy Effects on Bats and Birds

Smallwood¹,

Bell²,

Standish³

2020

J Wildl Manag

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As wind turbine‐caused mortality of birds and bats increases with increasing wind energy capacity, accurate fatality estimates are needed to assess effects, identify collision factors, and formulate mitigation. Finding a larger proportion of collision victims reduces the magnitude of adjustment for the proportion not found, thus reducing opportunities for bias. We tested detection dogs in trials of bat and small‐bird carcasses placed randomly in routine fatality monitoring at the Buena Vista and Golden Hills Wind Energy projects, California, USA, 2017. Of trial carcasses placed and confirmed available before next‐day fatality searches, dogs detected 96% of bats and 90% of small birds, whereas humans at a neighboring wind project detected 6% of bats and 30% of small birds. At Golden Hills dogs found 71 bat fatalities in 55 searches compared to 1 bat found by humans in 69 searches within the same search plots over the same season. Dog detection rates of trial carcasses remained unchanged with distance from turbine, and dogs found more fatalities than did humans at greater distances from turbines. Patterns of fatalities found by dogs within search plots indicated 20% of birds and 4–14% of bats remained undetected outside search plots at Buena Vista and Golden Hills. Dogs also increased estimates of carcass persistence by finding detection trial carcasses that the trial administrator had erroneously concluded were removed. Compared to human searches, dog searches resulted in fatality estimates up to 6.4 and 2.7 times higher for bats and small birds, respectively, along with higher relative precision and >90% lower cost per fatality detection. © 2020 The Authors. The Journal of Wildlife Management published by Wiley Periodicals, Inc. on behalf of The Wildlife Society.

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Response to Huso and Erickson's comments on novel scavenger removal trials

Cited by 12 publications

References 14 publications

Comparing bird and bat fatality‐rate estimates among North American wind‐energy projects

Comparing bird and bat fatality‐rate estimates among North American wind‐energy projects

Estimating wind turbine fatalities using integrated detection trials

Dogs Detect Larger Wind Energy Effects on Bats and Birds

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