Samantha J. Song

Calibrating indices of avian density from non-standardized survey data: making the most of a messy situation

Summary The analysis of large heterogeneous data sets of avian point-count surveys compiled across studies is hindered by a lack of analytical approaches that can deal with detectability and variation in survey protocols. We reformulated removal models of avian singing rates and distance sampling models of the effective detection radius (EDR) to control for the effects of survey protocol and temporal and environmental covariates on detection probabilities. We estimated singing rates and EDR for 75 boreal forest songbird species and found that survey protocol, especially point-count radius, explained most of the variation in detectability. However, environmental and temporal covariates (date, time, vegetation) affected singing rates and EDR for 73% and 59% of species, respectively. Unadjusted survey counts increased by an average of 201% from a 5-min, 50-m radius survey to a 10-min, 100-m radius survey (n = 75 species). This variability was decreased to 8·5% using detection probabilities estimated from a combination of removal and distance sampling models. Our modelling approach reduced computation when fitting complex models to large data sets and can be used with a wide range of statistical techniques for inference and prediction of avian densities.

Predation in heterogeneous forests: A comparison at natural and anthropogenic edges

The boreal mixed-wood forest is a naturally heterogenous system that has an extensive amount of forest edge. Recent increases in timber harvesting as well as oil and gas exploration have imposed an...

Using Binomial Distance-Sampling Models to Estimate the Effective Detection Radius of Point-Count Surveys Across Boreal Canada

ABSTRACT. We used binomial distance-sampling models to estimate the effective detection radius (EDR) of point-count surveys across boreal Canada. We evaluated binomial models based on 0–50 m and >50 m distance categories for goodness-of-fit and sensitivities to variation in survey effort and habitats sampled. We also compared binomial EDRs to Partners in Flights maximum detection distances (MDD) to determine differences in landbird population sizes derived from each. Binomial EDRs had a small positive bias (4%) averaged across 86 species and a large positive bias (30–82%) for two species when compared with EDRs estimated using multinomial distance sampling. Patterns in binomial EDRs were consistent with how bird songs attenuate in relation to their frequencies and transmission through different habitats. EDR varied 12% among habitats and increased 17% when birds were counted to an unlimited distance, compared with a limited distance of 100 m. The EDR did not vary with the duration of surveys, and densities did not differ when using unlimited-distance versus truncated data. Estimated densities, however, increased 19% from 3- to 5-min counts and 25% from 5- to 10-min counts, possibly from increases in the availability, movement, or double counting of birds with longer counts. Thus, investigators should be cautious when comparing distance-sampling results among studies if methods vary. Population sizes estimated using EDR averaged 5 times (0.8–15 times) those estimated with MDD. Survey data from which to estimate binomial EDRs are widely available across North America and could be used as an alternative to MDD when estimating landbird population sizes.

Boreal bird abundance estimates within different energy sector disturbances vary with point count radius

ABSTRACT Responses of boreal birds to changes in forest structure and composition caused by construction of well pads, seismic lines, and pipelines are poorly understood. Bird species associated with older forests are predicted to experience larger population declines with increased disturbance compared with species associated with younger or open habitats; however, point count methods may influence apparent outcomes because the proportional area of disturbed vegetation and the magnitude, uncertainty, and detection of a disturbance response by birds vary as a function of sampling area. We analyzed point count data from 12 energy sector studies and measured how disturbance type and point count radius interacted to affect 531 impact ratios (mean abundance at point counts centered within disturbances relative to abundance at point counts within forest 150–400 m from the nearest edge bordering those disturbances [59 species*3 disturbance types*3 point count radii]). We observed larger disturbance effects (impact ratios) within larger-radius point counts at well pads (100-m and unlimited-distance) and pipelines (unlimited-distance) compared with 50-m point counts at seismic lines, and within 50-m point counts at well pads relative to 50-m point counts at seismic lines. Effect uncertainty was higher at well pads and pipelines than seismic lines, and lower within larger-radius point counts. The probability of detecting a disturbance response was greater for larger-radius point counts at pipelines than for 50-m point counts at seismic lines, and within 50-m point counts at well pads relative to 50-m point counts at seismic lines. On average, a species was more likely to increase in abundance near an energy sector disturbance if the species was not associated with older (>75 yr) forest stages. While the effects of disturbance varied by species and with disturbance type, the effects of pipelines and seismic lines were better detected by larger-radius point counts, while the effects of well pads were better detected by smaller-radius point counts.

Evaluating time-removal models for estimating availability of boreal birds during point count surveys: Sample size requirements and model complexity

ABSTRACT We used conventional and finite mixture removal models with and without time-varying covariates to evaluate availability given presence for 152 bird species using data from point counts in boreal North America. We found that the choice of model had an impact on the estimability of unknown model parameters and affected the bias and variance of corrected counts. Finite mixture models provided better fit than conventional removal models and better adjusted for count duration. However, reliably estimating parameters and minimizing variance using mixture models required at least 200–1,000 detections. Mixture models with time-varying proportions of infrequent singers were best supported across species, indicating that accounting for date- and time-related heterogeneity is important when combining data across studies over large spatial scales, multiple sampling time frames, or variable survey protocols. Our flexible and continuous time-removal modeling framework can be used to account for such heterogeneity through the incorporation of easily obtainable covariates, such as methods, date, time, and location. Accounting for availability bias in bird surveys allows for better integration of disparate studies at large spatial scales and better adjustment of local, regional, and continental population size estimates.

Emulating natural disturbance through harvest: responses of upland and riparian cavity-users in the boreal plains mixedwood forest

.......................................... ................................................................................ i ACKNOWLEDGEMENTS................................................................................................... ii RESEARCH QUESTIONS AND OBJECTIVES .................. ................................................... 1 Objectives from original proposal .................. ....................................................................... 1 Change in research objectives...................... .......................................................................... 2 KEY FINDINGS.................................................................................................................... 2 1. Determine the structure of cavity nest webs and identify keystone cavity producers in aspen-dominated mixedwood. ........................................................................................ 2 2. Characterize key features of cavities, cavity tr ees, and stands used by primary excavators and secondary users. ............................... ............................................................................... 3 Cavity trees and surrounding trees.............................................................................. 3 Stand use in unharvested landscape.......................................................................... 3 3. Integrate our results with other research on cav ity nesting communities in Canadian forests, in particular with SFMN research conducted on nests webs in British Columbia......... 5 4. Determine the influence on cavity-using communit ies of new harvesting practices that attempt to approximate structures and patterns left following fire ......................................... 5 A. Is the structure of the excavating guild similar n the intact and harvested landscapes and how does amount of residual structure affect oc urrence of excavators (AB, SK, MB)?5 B. Are rates of cavity reuse, the structure of cavi ty nest webs, and the role of keystone cavity producers similar in the intact and single-p ass harvested landscapes (AB and SK)?.. 6 C. What is the influence of the type and amount of structure retained in single-pass landscapes on nest site selection by excavators? ... ............................................................ 7 KEY DELIVERABLES................................... .......................................................................... 9 BENEFITS TO PROJECT PARTNERS AND OTHERS...................................................... 10 MANAGEMENT/POLICY IMPLICATIONS...................................................................... 10 SUGGESTIONS FOR FUTURE RESEARCH.................... ................................................... 11 REFERENCES .................................................................................................................. 11