Correlates of Annual Stopover Counts in Two Species of Arctic-Breeding Shorebirds: Roles of Local, Breeding, and Climactic Drivers
This package contains the code from the manuscript:
Correlates of Annual Stopover Counts in Two Species of Arctic-Breeding Shorebirds: Roles of Local, Breeding, and Climactic Drivers
David Hope, Anna Drake, Daniel Shervill1, Moira J. F. Lemon, and Mark C. Drever
Follow SidneyIslandAnalysis_Guide.Rmd to recreate the analysis.
Figure 1. Map of study site on Sidney Island, British Columbia, Canada, where Western and Least Sandpipers were counted during southward migration, July and August, 1990 to 2018. Survey route is shown by a dashed line on the main figure, with the solid lines indicating the boundaries of Gulf Islans National Par Preserve, Sidney Spit Marine Park. The site’s location is shown by the star in the lower left map, and the box in the lower right map.
Figure 2. Seasonal trends in proportion of juveniles identified (A, B),
seasonal trends in average daily counts (C,D) and interannual trends in average daily counts (E,F)
in Western Sandpipers (top row; A,C,E) and Least Sandpipers (bottom row; B,D, F) at Sidney Island,
BC between 1990 and 2018. Mean ± 95% CI values are shown. Lines show the average trend from the
models described in the text with associated 95% confidence intervals (grey shading).
For C-F adults are shown with solid lines and circles and juveniles with dashed lines and triangles.
Figure 3. Standardized estimates of fixed effects from models explaining interannual variation in abundances at Sidney Island, BC in adult (circles) and juvenile (triangles) Western and Least Sandpipers. Estimates show the value ± 95% CI derived from either models with a single value added above the baseline seasonal trend (black) or in a full model for a particular hypothesis (grey). Only models that have moderate support from the data (∆AICc< 6) are shown. We did not include the interannual trend models in this figure. Models are grouped by referring those exploring the effect of adult numbers on juvenile numbers (“Age”), variables related to the breeding grounds (“Breeding”), broad scale climactic variables (“Global”), or weather variables collected near the stopover site (“Local”).
Figure 4. Predicted model trends in counts of Western and Least Sandpipers from models that explain interannual variation in counts of each species. Only variables with relatively strong effects from models with moderate support from the data are shown (See Fig. 3). Mean estimated counts for each year are shown in dots, with the year indicated and the size of the dot indicating the number of surveys conducted.
Figure 5. Trends in annual abundances between adult and juvenile Western (solid line, black triangles) and Least Sandpipers (dashed line, grey dots) at Sidney Island, BC between 1990 and 2018. The lines show the estimated trend in counts with associated 95% confidence intervals from a model that predicted the effect of the adult random intercept from the baseline model on the abundance of juveniles in each year. Points show the adult versus juvenile fixed plus random intercepts from the baseline models for each year to represent numbers at the peak of each migration. Abundances and trends for both adults and juveniles are estimated using log-counts and back transformed to linear scale for presentation here.