Métodos

 

violin plot-all species-spanish

La traducción en Español pronto estará disponible.

Conservation Status Assessment

The 2016 State of North America’s Birds (SONAB) report is based on a conservation status assessment of 1,154 native bird species that breed in the continental U.S., Canada, and Mexico, as well as oceanic birds that regularly occur in waters off these three countries. Every bird species was assessed throughout its range and annual cycle. This assessment employs biological criteria to evaluate distinct components of vulnerability, including population size, distribution, threats and population trend. The process was developed and refined over many years (Hunter et al. 1993, Carter et al. 2000, Panjabi et al. 2001, Panjabi et al. 2005, Panjabi et al. 2012) and has been updated in response to external peer review (Beissinger et al. 2000) and partner input. It is explained in detail in the Partners in Flight Handbook on Species Assessment (Panjabi et al. 2012).

Although Partners in Flight originally applied this assessment to all landbirds in the U.S. and Canada (Rich et al. 2004), it was recently expanded to include all bird species occurring in Mexico (Berlanga et al. 2010). For this report, the State of North America’s Birds science team applied identical methods to assess all North American taxa, seeking expert review for scores applied to shorebirds, waterbirds, seabirds, and waterfowl. All assessment scores, and associated information on every species, is housed in the Avian Conservation Assessment Database, available at (LINK). The Resources section of this site includes a summary of assessment information used in this report as well as a downloadable version of the entire data table.

Each species was assigned a numerical score from 1 to 5 for each of six biological factors that assess largely independent aspects of vulnerability at the rangewide or North American scale: Population Size (PS), Breeding Distribution (BD), Nonbreeding Distribution (ND), Threats to Breeding (TB), Threats to Nonbreeding (TN), and Population Trend (PT). Each score reflects the degree of vulnerability inherent to the species due to that factor, ranging from low (1) to high (5) vulnerability.

For each species we calculated a Combined Breeding Score (TB + BD + PT + PS) and a Combined Nonbreeding Score (TN + ND + PT + PS) and selected the higher of the two as the Maximum Combined Conservation Score (CCSmax). This score can range from 4 for a widespread, relatively secure species, to 20 for a species of the very highest concern. Species with CCSmax ≥ 14, or species with CCSmax = 13 and PT = 5 (steeply declining trend) were identified as comprising the SONAB Watch List; these species are of highest vulnerability to extinction based on elevated scores across multiple factors.

Analysis Methods for State of North America’s Birds

We categorized each species’ overall conservation concern status as low, moderate, or high. High concern species were those included on the SONAB Watch List. Moderate concern were species with a maximum combined score > 8 but not high enough to warrant inclusion on the Watch List. Species were considered low concern if their maximum combined score was 8 or less.

The sizes of the bars in the report’s bar graphs reflect, for a given group of species, the proportions of species that are low (blue), moderate (orange), and high concern (red, i.e., these are species on the Watch List). The bars are centered on the division between moderate and high concern, so that the red bars to the right of the centering line provide a quick visual comparison of the proportion of species on the Watch List.

This document includes more detailed graphical summaries that complement the three-category bar graphs in the main report and provide a more nuanced view of the conservation status of each group. The graphs that follow show the proportions of species in each of the 17 levels of the concern scale (the concern scores range from 4 to 20 and are labeled at the bottom of each graph). These graphs can be interpreted in a similar way to violin plots or a histogram; the size of each of the 17 vertical bars indicates the proportion of species from the group with that concern score. Each vertical bar is centered on the solid gray line, and the two dotted gray lines indicate the size of a bar that would represent 10% of the species in the group.

Note: as previously mentioned, species with a maximum combined score of 13 and a population trend score of 5 were considered high conservation concern and included in the Watch List; for the purposes of all graphs in the report and in this document, these species were graphed as if their CCSmax score was 14 (i.e., to the right of the high-concern threshold line).

Overall, these more detailed graphs convey the same main messages as in the report, that Oceans and Tropical Forest species are in crisis. The added detail also shows that relative to other groups, many of the Ocean and Tropical Forest species are at the highest level of conservation concern (dark red bars for scores 19 and 20). These graphs also highlight the fact that even groups that are doing relatively well overall (i.e., wetlands and temperate forests) also include some species at the highest conservation levels. Finally, the graphs provide a more nuanced ranking of the overall average status of these species groups: for example, although the proportions of species on the Watch List are very similar for Temperate Forests, Tundra, Wetlands, and Boreal Forest, almost all of the high-concern species in the Boreal Forest are only just beyond the high-concern threshold.

This page presents 7 detailed graphs: one to match each of the 7 bar graphs in the main report.

Composite population trajectories for Coasts and Grasslands

The composite population trajectories in the Coasts and Grasslands sections of the report were created using the same approach applied in the 2012 State of Canada’s Birds and the U.S. State of the Birds reports for 2009 and 2014. Briefly, the composite population trajectory (i.e., the trendline) represents the average population status of species in the group, relative to the start year. The average is calculated using a hierarchical Bayesian statistical model that accounts for the precision of each species’ population status information. The Coasts graph used population status estimates for each species, derived from analyses of three shorebird migration surveys that use the same survey protocol: the International Shorebird Survey, organized by the Manomet Center for Conservation Sciences; and the Atlantic Canada Shorebird Survey and the Ontario Shorebird Survey, both of which are organized by Environment and Climate Change Canada. The Grasslands graph used population status estimates derived from the North American Breeding Bird Survey. Note: the vertical scaling of these composite trajectory graphs is not linear. The nonlinear scaling is necessary to reflect the fact that proportional changes in population size are also nonlinear (e.g., a 100% increase, a doubling, is required for a population to recover from a 50% decrease in population size).

Literature Cited

Beissinger, S.R., J.M. Reed, J.M. Wunderle, Jr., S.K. Robinson, and D.M. Finch. 2000. Report of the AOU Conservation Committee on the Partners in Flight species prioritization plan. Auk 117:549–561.

Carter, M.F., W.C. Hunter, D.N. Pashley, and K.V. Rosenberg. 2000. Setting conservation priorities in the United States: the Partners in Flight approach.  Auk 117:541–548.

Hunter, W.C., M.F. Carter, D.N. Pashley, and K. Baker. 1993. The Partners in Flight prioritization scheme. Pages 109–119 in Status and Management of Neotropical Migratory Birds (D. Finch and P. Stangel, eds.). USDA Forest Service General Technical Report RM-229. USDA Forest Service, Fort Collins, Colorado.

Panjabi, A., C. Beardmore, P. Blancher, G. Butcher, M. Carter, D. Demarest, E. Dunn, C. Hunter, D. Pashley, K. Rosenberg, T. Rich, and T. Will. 2001. The Partners in Flight handbook on species assessment and prioritization. Version 1.1, December 2001. Partners in Flight Technical Series No. 3. Partners in Flight.

Panjabi, A.O., E.H. Dunn, P.J. Blancher, W.C. Hunter, B. Altman, J. Bart, C.J. Beardmore, H. Berlanga, G.S. Butcher, S.K. Davis, D.W. Demarest, R. Dettmers, W. Easton, H. Gomez de Silva Garza, E.E. Iñigo-Elias, D.N. Pashley, C.J. Ralph, T.D. Rich, K.V. Rosenberg, C.M. Rustay, J.M. Ruth, J.S. Wendt, and T.C. Will. 2005. The Partners in Flight handbook on species assessment. Version 2005. Partners in Flight Technical Series No. 3. Partners in Flight.

Panjabi, A.O., P. J. Blancher, R. Dettmers, and K.V. Rosenberg. 2012. The Partners in Flight handbook on species assessment. Version 2012. Partners in Flight Technical Series No. 3. Partners in Flight.