Bias in estimated breeding-bird abundance from closure-assumption violations

Fogarty, Frank A.; Fleishman, Erica

doi:10.1016/j.ecolind.2021.108170

Cited by 13 publications

(25 citation statements)

References 42 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The MNCM, such as the related N-mixture model (Royle, 2004) and MRCM (Sutherland et al, 2016), implicitly assumes all sites are closed to movement during the survey window. The mobility of birds and previous analyses suggest that our data violate the closure assumption (Fogarty & Fleishman, 2021). However, if the closure assumption is relaxed, these models can accurately estimate superpopulation abundance, and covariate estimates in N-mixture models are robust to large and realistic amounts of within-survey movement (Fogarty & Fleishman, 2021).…”

Section: Multiple-region Mncmsmentioning

confidence: 72%

Multiple‐region,N‐mixture community model to assess associations of riparian area, fragmentation, and species richness

Fogarty

Yen

Fleishman

et al. 2022

Ecological Applications

Self Cite

View full text Add to dashboard Cite

The associations of habitat area and fragmentation with species richness long have been major topics within community ecology. Recent discussion has focused on properly assessing fragmentation independent of habitat area (fragmentation per se), and on whether fragmentation has significant negative or positive associations with species richness. We created a novel, multiple‐region, N‐mixture community model (MNCM) to examine the relations of riparian area and fragmentation with species richness of breeding birds in mountain ranges within the Great Basin, Nevada, USA. Our MNCM accounts for imperfect detection in count data at the survey‐point level while allowing comparisons of species richness among regions in which those points are embedded. We used individual canyons within mountain ranges as regions in our model and measured riparian area and the Normalized Landscape Shape Index, a metric of fragmentation that is independent of total riparian area. We found that riparian area, but not its fragmentation, was a primary predictor of canyon‐level species richness of both riparian obligates and all species. The relationship between riparian area and riparian obligate species richness was nonlinear: canyons with ≥25 ha woody riparian vegetation had relatively high species richness, whereas species richness was considerably lower in canyons with <25 ha. Our MNCM can be used to calculate other metrics of diversity that require abundance estimates. For example, Simpson's evenness of riparian obligate species had a weak negative association with riparian area and was not associated with fragmentation. Projections of future riparian contraction suggested that decreases in species richness are likely to be greatest in canyons that currently have moderate (~10–25 ha) amounts of riparian vegetation. Our results suggest that if a goal of management is to maximize the species richness of breeding birds in montane riparian areas in the Great Basin, it may be more effective to focus on total habitat area than on fragmentation of patches within canyons, and that canyons with at least moderate amounts of riparian vegetation should be prioritized.

show abstract

Section: Multiple-region Mncmsmentioning

confidence: 72%

Multiple‐region,N‐mixture community model to assess associations of riparian area, fragmentation, and species richness

Fogarty

Yen

Fleishman

et al. 2022

Ecological Applications

Self Cite

View full text Add to dashboard Cite

show abstract

“…One advantage of using remotely sensed tagging data for analyses with the MSORD-SU model is that there is minimized negative bias in the derived phenological parameters [ 32 ]. Since detection of previously tagged birds in the study area is high ( ρ = 0.57 : 0.84) [ 56 ], low tagging effort is not expected to strongly influence arrival estimates. However, because our primary and secondary sampling periods are configured over a contiguous temporal range, mortality during secondary sampling periods is a source of negative bias in estimates of both

and ρ [ 32 ].…”

Section: Discussionmentioning

confidence: 99%

Quantifying phenology and migratory behaviours of hummingbirds using single-site dynamics and mark-detection analyses

et al. 2022

View full text Add to dashboard Cite

Nuanced understanding of seasonal movements of partially migratory birds is paramount to species and habitat conservation. Using nascent statistical methods, we identified migratory strategies of birds outfitted with radio-frequency identification (RFID) tags detected at RFID feeders in two sites in California, USA. We quantified proportions of migrants and residents and the seasonal phenology for each movement strategy in Allen’s and Anna’s hummingbirds; we also validated our methodology by fitting our model to obligate migratory black-chinned hummingbirds. Allen’s and Anna’s hummingbirds exhibited characteristics of facultative migratory behaviour. We also quantified apparent annual survival for each migratory strategy and found that residents had significantly higher probabilities of apparent survival. Low survival estimates for migrants suggest that a high proportion of birds in the migrant group permanently emigrated from our study sites. Considered together, our analyses suggest that hummingbirds in both northern and southern California sites partake in diverse and highly plastic migratory behaviours. Our assessment elucidates the dynamics underlying idiosyncratic migratory behaviours of two species of hummingbirds, in addition to describing a framework for similar assessments of migratory behaviours using the multi-state open robust design with state uncertainty model and single-site dynamics.

show abstract

“…Given the presence of bias in λ , the use of HMs for inferring the site use frequency λ use could be an alternative that provides reliable answers to many wildlife related questions. Site use frequency is effectively a product of population size and HRA, hence reflects both the true number of animals present N , as well as their movement pattern (Chandler et al, 2011; Nakashima, 2020; Fogarty and Fleishman, 2021). Our results suggest that HMs do not necessarily estimate λ use more accurately than λ .…”

Section: Discussionmentioning

confidence: 99%

“…There have been several studies that assess the performance of HMs under the violation of these assumptions (i-iv). While few authors have focused on the BernP so far, the BP model has been evaluated in more depth: Fogarty and Fleishman (2021) show that even small violations of the closure assumption lead to substantial bias in abundance estimated from BP. Moreover, accidental double counting of individuals, which can be viewed as false positive detections, resulted in strong positive biases in this model (Link et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

“…In CT surveys temporally replicated counts are collected at a set of spatial locations, which are informative about animal abundance. Typically, abundance represents a fixed number of individuals at a site for the entire study period (also referred to as season-long abundance; Fogarty and Fleishman, 2021). However, this classical conception of abundance is closely tied to individuals remaining at their site, and abundance models typically do not estimate this quantity well when individuals move across sites.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Simulation-based assessment of the performance of hierarchical abundance estimators for camera trap surveys

Martijn

Casaer

Beenaerts

et al. 2022

Preprint

View full text Add to dashboard Cite

The need for knowledge about abundance to guide conservation and management strategies in combination with low detectability of many species has led to a widespread use in ecology and management of a range of hierarchical models (HMs) for abundance. These models also appear like good candidates for inference about local abundance in nature reserves studied by camera traps. However, the best choice among these models is unclear, particularly how they perform in the face of several complicating features of realistic populations that include: (i) movements relative to sites, (ii) multiple detections of unmarked individuals within a single survey, and (iii) low probabilities of detection. We conducted a simulation-based comparison of three HMs (Royle-Nichols, binomial Nmixture and Poisson N-mixture model) in the context of small populations of elusive animals in a single study area, where animals cannot be distinguished individually and hence double counting occurs. We generated count data by simulating camera traps monitoring individuals moving according to a Gaussian random walk. Under the simulated scenarios none of the three HMs yielded accurate abundance estimates. Moreover, the performance of each HM depended on the interpretation of abundance. By pooling abundance estimates for trend estimation, each models performance markedly improves. Overall, the Royle-Nichols and Poisson N-mixture models outperform a binomial N-mixture model. This emphasizes the importance of choosing the appropriate HM for the data problem.

show abstract

Bias in estimated breeding-bird abundance from closure-assumption violations

Cited by 13 publications

References 42 publications

Multiple‐region,N‐mixture community model to assess associations of riparian area, fragmentation, and species richness

Multiple‐region,N‐mixture community model to assess associations of riparian area, fragmentation, and species richness

Quantifying phenology and migratory behaviours of hummingbirds using single-site dynamics and mark-detection analyses

Simulation-based assessment of the performance of hierarchical abundance estimators for camera trap surveys

Contact Info

Product

Resources

About