Variability in Grassland Bird Counts Related to Observer Differences and Species Detection Rates

Diefenbach, Duane R.; Brauning, Daniel W.; Mattice, Jennifer A.

doi:10.1093/auk/120.4.1168

Cited by 69 publications

(79 citation statements)

References 11 publications

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“…We speculate that relatively low detectability of Grasshopper Sparrow songs were because they were both quiet and high‐frequency (see also Diefenbach et al. ); a large portion of their song (ca. 4–11 kHz; Vickery ) is above the peak human hearing sensitivity of 1–6 kHz (Davis ).…”

Section: Discussionmentioning

confidence: 96%

Effects of ambient noise on detectability and localization of avian songs and tones by observers in grasslands

Koper

Leston

Baker

et al. 2015

Ecology and Evolution

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Probability of detection and accuracy of distance estimates in aural avian surveys may be affected by the presence of anthropogenic noise, and this may lead to inaccurate evaluations of the effects of noisy infrastructure on wildlife. We used arrays of speakers broadcasting recordings of grassland bird songs and pure tones to assess the probability of detection, and localization accuracy, by observers at sites with and without noisy oil and gas infrastructure in south‐central Alberta from 2012 to 2014. Probability of detection varied with species and with speaker distance from transect line, but there were few effects of noisy infrastructure. Accuracy of distance estimates for songs and tones decreased as distance to observer increased, and distance estimation error was higher for tones at sites with infrastructure noise. Our results suggest that quiet to moderately loud anthropogenic noise may not mask detection of bird songs; however, errors in distance estimates during aural surveys may lead to inaccurate estimates of avian densities calculated using distance sampling. We recommend caution when applying distance sampling if most birds are unseen, and where ambient noise varies among treatments.

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Section: Discussionmentioning

confidence: 96%

Effects of ambient noise on detectability and localization of avian songs and tones by observers in grasslands

Koper

Leston

Baker

et al. 2015

Ecology and Evolution

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“…However, grasslands showed a high species richness associated with a high variance. This high variance in estimated species richness is likely owing to the usually low detection probability of grassland species (Diefenbach et al. , 2003) likely due to higher predation rates in open landscapes (Boulinier et al.…”

Section: Discussionmentioning

confidence: 99%

The impact of shrub encroachment on savanna bird diversity from local to regional scale

Sirami

Seymour

Midgley

et al. 2009

Diversity and Distributions

104

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Aim Evidence is accumulating of a general increase in woody cover of many savanna regions of the world. Little is known about the consequences of this widespread and fundamental ecosystem structural shift on biodiversity.Location South Africa. Methods We assessed the potential response of bird species to shrub encroachment in a South African savanna by censusing bird species in five habitats along a gradient of increasing shrub cover, from grassland/open woodland to shrubland dominated by various shrub species. We also explored historical bird species population trends across southern Africa during the second half of the 20th century to determine if any quantifiable shifts had occurred that support an ongoing impact of shrub encroachment at the regional scale.Results At the local scale, species richness peaked at intermediate levels of shrub cover. Bird species composition showed high turnover along the gradient, suggesting that widespread shrub encroachment is likely to lead to the loss of certain species with a concomitant decline in bird species richness at the landscape scale. Finally, savanna bird species responded to changes in vegetation structure rather than vegetation species composition: bird assemblages were very similar in shrublands dominated by Acacia mellifera and those dominated by Tarchonanthus camphoratus.Main conclusions Shrub encroachment might have a bigger impact on bird diversity in grassland than in open woodland, regardless of the shrub species. Species recorded in our study area were associated with historical population changes at the scale of southern Africa suggesting that shrub encroachment could be one of the main drivers of bird population dynamics in southern African savannas. If current trends continue, the persistence of several southern African bird species associated with open savanna might be jeopardized regionally. KeywordsBiome shift, bush encroachment, global change, land cover change, landscape heterogeneity. Diversity and Distributions, (Diversity Distrib.) (2009) 15, 948-957

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“…When approached on foot they would run away from the person and then fly long distances (>50 m) several times before being captured. When approached on the ATV, we could get within approximately 3 m without the bird moving, possibly because of the “background noise” of the ATV engine (Olinde et al , Diefenbach et al ).…”

Section: Resultsmentioning

confidence: 99%

Nocturnal distance sampling all‐terrain vehicle surveys for nonbreeding rails

Fournier

Krementz

2017

Wildl. Soc. Bull.

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Rails (Family: Rallidae) are among the most difficult birds to detect. Although methods have been developed to optimize detection during the breeding season, there is no current suitable survey method for the nonbreeding season. Low detection of rails and lack of suitable methods limit monitoring efforts and examination of important questions related to rail conservation and habitat management during the nonbreeding season. We present a new survey method along with suggestions for its effective use in moistsoil wetlands. We conducted nocturnal surveys during the autumns 2012-2015 in Missouri, USA, to detect sora (Porzana carolina) using hierarchical generalized distance sampling along transects that we traveled while riding all-terrain vehicles at night. We evaluated assumptions of our survey method by examining the response by radiomarked sora to survey vehicles and comparing survey counts between surveys on the same night. These surveys produced sora density estimates with error that can be used to address conservation and management questions such as habitat use and migratory timing. Published 2017. This article is a U.S. Government work and is in the public domain in the USA.

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Variability in Grassland Bird Counts Related to Observer Differences and Species Detection Rates

Cited by 69 publications

References 11 publications

Effects of ambient noise on detectability and localization of avian songs and tones by observers in grasslands

Effects of ambient noise on detectability and localization of avian songs and tones by observers in grasslands

The impact of shrub encroachment on savanna bird diversity from local to regional scale

Nocturnal distance sampling all‐terrain vehicle surveys for nonbreeding rails

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