Introduction and methods




Large-scale and long-term population monitoring programs are an essential element in bird conservation. These programs provide information that can be used to determine population status and highlight species in need of conservation action. Monitoring results can also be used to determine the impact of management actions and, in some cases, can help to identify the causes of population change. The species accounts presented here highlight the way in which these monitoring programs can be used to establish baseline population levels and to identify important changes in bird populations over the past 40-some years.

The focus of this website is to use the best available results from bird monitoring programs to assess the current (1970-2014) national population status of each species. This iteration of the website includes all bird species that breed or regularly occur in Canada, including some at the subspecies/population level. Earlier iterations (1970-2010, 1970-2011) can be viewed in the website archives.

These species accounts are regularly reviewed and updated to reflect the most recent population trend data. Updates will also help track progress in how well birds are monitored in Canada. As more monitoring data are accumulated and analytical methods improved, the reliability of the population assessments presented here should increase and fewer species should be considered data deficient. In this third release of the website, the population status for each species is assessed relative to circa 1970 (i.e., late 1960s to early 1970s) or as close as data allow. This time period was selected as the reference point both because there are few data previous to this period for most species, and because it is feasible to base conservation objectives on population levels at that time. However, 1970 is not an appropriate reference point for all species including, for example, species at risk whose populations are very small or raptors and other birds that experienced dramatic declines in the 1950s and 1960s due to DDT and were at very low levels in 1970.

Environment Canada is currently developing methods to set a national population goal for each species in Canada in order to better assess progress towards maintaining migratory bird populations. Once completed, these species-specific goals will be used as the reference point in future iterations of the Status of Birds in Canada website against which progress on conservation can be measured.

Data sources

To determine population status, the available results of all monitoring programs for each species were examined and the most reliable source(s) for assessing the long-term, national status was used. Canadian results from the North American Breeding Bird Survey (BBS) in Canada (Environment Canada 2014) were used preferentially for landbirds. If BBS did not adequately cover the species, other sources were used either instead of or to supplement the BBS. Some birds that breed in northern Canada, beyond the region covered by the BBS, spend their winters in the United States and more southern parts of Canada where their populations are monitored by the Christmas Bird Count (CBC) (results supplied by National Audubon Society and Environment Canada). CBC results were used to assess many of these northern landbird species and to supplement the information available for other species. Results from other sources such as the provincial breeding bird atlases and species-specific surveys were also used for some landbirds. For other species groups, aerial waterfowl surveys, shorebirds migration surveys, seabird colony counts, coastal water bird counts, marsh monitoring programs and a variety of species-specific surveys were used.


2.1 Designations

A variety of species’ designations are presented, including: the International Union for the Conservation of Nature (IUCN) Red List of Threatened Species (IUCN 2014), the Committee on the Status of Endangered Wildlife in Canada (COSEWIC), Wild Species 2010: the general status of species in Canada (Canadian Endangered Species Conservation Council, 2011), Partners in Flight’s (PIF) North American Landbird Conservation Plan (Rich et al. 2004), Saving Our Shared Birds: Tri-National Vision for Landbird Conservation (Berlanga et al. 2010), priority species listed in the North American Bird Conservation Initiative’s (NABCI) Bird Conservation Strategies and, for waterfowl, the North American Waterfowl Management Plan’s (NAWMP 2004) population goals.

These designations differ in scale, scope and in timing leading to possible differences among designations for any one species. For example, the IUCN Red List identifies wildlife species threatened with extinction on a global scale whereas COSEWIC evaluates the risk of extinction for wildlife species in Canada. Only a small portion of species are assessed or re-assessed by COSEWIC and IUCN in any one year. Assessments for the Wild Species report are conducted every 5 years and provide a coarse-scaled summary of the status of species in Canada that allows species to be prioritized in terms of the effort and attention needed to prevent their further decline or loss, or to indicate when more information is needed. In Wild Species the definition for "Secure" includes all species that are not thought to belong in the “At Risk” or “Sensitive” categories. The Secure category can include species that show a decline in numbers in Canada but remain relatively widespread or abundant. Note also, that Wild Species designations are always made at the species level, while COSEWIC may treat subspecies, varieties or populations separately. COSEWIC may also designate species for reasons other than population decreases (e.g. small population size, degree of threats).

An example of differences among these designations can be seen in the designations for Eastern Meadowlark. The Eastern Meadowlark has been designated as Threatened in Canada (COSEWIC 2011) but not at the global level (Least Concern; IUCN Red List 2014). It is currently considered "Secure" in Canada according to Wild Species 2010, and it was not included in PIF’s 2004 Landbird Conservation Plan as a Watch List or a Stewardship Species. However, on the Status of Birds in Canada website, it is assessed as having experienced a large decrease in abundance since 1970; suggesting some concern for the population. It is also considered a “Priority” species in four of NABCI’s Bird Conservation Strategies.

2.2 Determining population status and reliability

For all species except waterfowl, methods for determining the population status of each species and its reliability were based, with some modifications, on those developed by Blancher et al. (2009) to assess the population trend status of forest birds in Ontario. In the 2011 iteration of the website, one author was assigned to write each species; in this current version, all accounts were revised by the same author. To improve consistency among authors, written guidelines were provided as described below. Each account then underwent a detailed peer review by one or more Environment Canada bird experts.

Accounts for waterfowl were based on Environment Canada’s 2014 Population Status of Migratory Game Birds in Canada. Detailed methods can be found in that report (Canadian Wildlife Service Waterfowl Committee 2014).

2.2.1 Population trend data

The author assigned to a species assessed all available trend results in order to select the most appropriate source(s) and determine the change in its national population status relative to 1970. Results from the main bird surveys in Canada were provided, as available, at various geographic scales and time periods (Table 1). If available, both population trends and annual indices were provided. Most surveys are based on abundance data but for example, trends from the Atlas of the Breeding Birds of Ontario are based on detection/non-detection in atlas squares. Authors were also asked to investigate and use other appropriate sources of data that were not supplied (e.g. Canadian Migration Monitoring Network, species-specific surveys, sources in the published literature).

Table 1. Bird survey data supplied to authors for use in assessing bird population status
Survey Years Geographic area covered Source
North American Breeding Bird Survey (BBS) 1970 to 2012 Canada and Bird Conservation Regions Environment Canada
North American Breeding Bird Survey (BBS) 1966 to 2012 North America United States Geological Survey
Christmas Bird Count (CBC) 1965 to 2012 North America National Audubon cf. Candan et al. (in prep)
Christmas Bird Count (CBC) 1970 to 2012 Canada Environment Canada
Ontario Breeding Bird Atlas 1981-85 to 2001-05 Ontario Environment Canada
Forest Bird monitoring Program (FBMP) 1987 to 2011 Ontario Environment Canada
Shorebird Migration Monitoring 1974 to 2013 Canada and United States Environment Canada (using data from International Shorebird Survey, Ontario Shorebird Survey, Atlantic Canada Shorebird Survey
Great Lakes Marsh Monitoring Program 1995 to 2012 Great Lakes Basin Bird Studies Canada
Quebec Marsh Monitoring Program 2004 to 2013 Quebec Bird Studies Canada
Seabird Colony Counts 1984 to 2010 Coastal (eastern, western, arctic) Environment Canada
High Elevation Landbird Program (HELP) 2003 to 2011 New Brunswick and Nova Scotia Bird Studies Canada
British Columbia Coastal Waterbird Survey 1999 to 2011 British Columbia Bird Studies Canada
Great Lakes Decadal Colonial Waterbird Census 1976 to 2009 Great Lakes Basin U.S. Fish and Wildlife Service and Environment Canada
Nocturnal Owl Surveys 1995 to 2013,
2008 to 2013,
2001 to 2012
Atlantic provinces
Bird Studies Canada
International Piping Plover Census 1991 to 2011 Canada International Piping Plover Coordination Group
American Woodcock Singing Survey 1968 to 2014 Eastern Canada and North America U.S. Fish and Wildlife and Environment Canada
2.2.2 Assessing survey reliability

Authors assessed the reliability and accuracy of each survey to determine a) if results from a particular survey should be considered at all and b) the most appropriate survey(s) in cases where more than one source of information was available for a species. Where possible, three measures of reliability for each survey were considered: precision of the trend, coverage of the species’ breeding population or range and survey design. Precision analysis assessed the precision of the trend estimate to determine whether the available data could reliably detect biologically significant population trends; coverage analysis determined the proportion of a species’ breeding population or range covered by the survey; assessment of survey design examined the strengths, weaknesses and potential biases of the survey for each species. For BBS only, a fourth measure, model fit, was used to reflect the adequacy of some of the assumptions underlying the statistical model for the species in question. A more detailed description of this process is provided in the following sections.

a) Precision

For surveys analysed using a Hierarchical Bayesian model (e.g. Breeding Bird Survey, Christmas Bird Count, Shorebird Migration Monitoring) precision reflects the width of the 95% credible interval (upper limit – lower limit). For more details on BBS analysis see Environment Canada (2014). The 95% credible interval defines a range of trend values that have a 95% probability of including the true population trend value. Similar categories were used for surveys analysed by other means based on the width of the confidence interval (e.g. Great Lakes Marsh Monitoring Program, owl monitoring programs). The credible interval/confidence interval was then assigned to 3 categories of precision:

  • High: less than 3.5 width of credible interval/confidence interval
  • Medium: 3.5 - 6.7
  • Low: greater than 6.7

These categories indicate trend estimates that are sufficiently precise to confidently identify the following magnitudes of population declines over 20 years:

  • High: 30% decline
  • Medium: 50% decline
  • Low: category includes trends that are too imprecise to confidently identify a 50% population decline over 20 years

For the Atlas of the Breeding Birds of Ontario, a working standard error was derived from the upper and lower bounds on the slope as follows: the bounds were converted to the natural log scale and the difference between the upper and lower bounds divided by 4 was used as the working standard error. For some species, the lower bound for the slope from the Ontario Atlas was 0.0. In these cases, the reported slope was used instead of the lower bound and the resulting difference was divided by 2. For seabird colony counts and the Great Lakes Marsh Monitoring Program, precision was categorized based on the power to detect a 50% decline over a period of 20 years. The power was assigned to 3 categories:

  • High: greater than 80% power
  • Medium: 50% to 80% power
  • Low: less than 50% power

Precision estimates were not available for some surveys such as the Great Lakes Decadal Colonial Waterbird Census, species-specific surveys and, in some cases, information from published literature. In the case of seabirds, precision of the overall trend reflects variability in trend among surveys only, because many of the trends within individual surveys were lacking estimates of precision.

b) Coverage

Authors were provided with an estimate of the proportion of a species’ breeding population or the species’ range covered by a survey, as available; where this was not available, authors estimated coverage for surveys based on a coarse assessment of the species’ range and the survey coverage area.

For the BBS, coverage represents the proportion of the species’ breeding population within the area covered by the BBS. The reported value is a geometric average of the annual estimates. In a given year, the area covered is defined as the area within degree-blocks (1 degree longitude by 1 degree latitude) that contain routes contributing data to the analysis (Environment Canada 2014).

For the Shorebird Migration Monitoring survey, coverage was estimated by determining the mean number of individuals counted per year (for all sites and surveys during the fall migration combined), and expressing this as a percentage of the population estimate (population estimates were from Morrison et al. 2006). However, these percentages do not correspond directly to a percentage of the population surveyed, because each individual may have been counted more than once at a site, or may have been observed at multiple sites.

The percent of the Canadian population covered in Ontario by the Atlas of the Breeding Birds of Ontario was derived by the authors using estimates from the Partners in Flight Population Estimates database (Blancher et al. 2007).

The percent of a species’ North American range covered by the North American Christmas Bird Count results were provided from Butcher and Nevin (2007). Because these results include data from both the United States and Canada, authors estimated the coverage of the species in Canada using the North American coverage and the approximate proportion of the species’ North American range in Canada.

Reliability of survey coverage was assigned to three categories (based on Blancher et al. 2009):

  • High: greater than 50% covered (breeding population or range)
  • Medium: 25 to 50% covered
  • Low: less than 25% covered
c) Design

Authors made a subjective assessment of the reliability of survey design for each species. Descriptions of strengths, weaknesses and potential biases for each survey, developed by Environment Canada staff, were provided for consideration. Reliability of design was assigned to three categories (based on Blancher et al. 2009):

  • High: Little bias - survey design likely results in limited bias. Sources of bias likely to be relatively minor for this species.
  • Medium: Moderate bias - one or more sources of potentially important bias, but overall bias is not likely to reverse large increases or decreases.
  • Low: Large bias with potential to obscure large trends. Sources of bias may obscure or reverse even large increases or decreases.

Results from the Christmas Bird Count were usually considered less reliable if they were based partially on birds that may have spent the breeding season outside of Canada (e.g., continental trends for species that breed in both Canada and the United States). For some species, especially common species, the trends from the Ontario Atlas have been found to underestimate the magnitude of population change relative to trends from other surveys that are based on abundance data (Blancher et al. 2009). In these cases, the reliability of the Ontario Atlas result was downgraded.

Final reliability rating

The reliability rating given to each survey usually equaled the minimum rating of the above 3 or 4 reliability measures, but with some exceptions. If results were based on very low sample size they were generally not rated as "high” reliability unless the species only existed at the few sites being monitored. In some cases, survey reliability was downgraded if the trajectory of the annual index was strongly non-linear, showed a strongly cyclic population, or if the trend figure was strongly influenced by an idiosyncratic year(s) in the population trajectory of the annual indices. Reliability could be upgraded if the trend result was highly significant and the magnitude of the trend was very large even if other factors were low. For example, BBS results for the Wild Turkey have low precision but the magnitude of the annual trend (19.4%) leaves little doubt that an increase in the Wild Turkey population has occurred. Survey reliability could also be downgraded if there were substantially less than ~ 40 years of data and thus uncertainty about the species’ population status relative to 1970.

2.2.3 Assessing population status relative to 1970

Based on the reliability assessment (as described above) authors selected the most reliable, long-term survey as the primary source to use in determining the species’ national population status relative to 1970. The use of only one source was considered sufficient if the results of that survey were highly reliable, However, authors could also consider results from other surveys (secondary survey) if two highly reliable sources were available. When the primary survey reliability was medium or low, an additional data source (secondary source) was used if available to increase the validity. A third source (tertiary survey) was used if the reliability of all other sources was low and thus any corroboration was useful or where the third source demonstrated a different point (e.g., a regional population trend that differed significantly from the national trend). If available, a third source was also used to help corroborate the status in cases where the primary and secondary had similar reliability ratings but different results either in direction or magnitude. Survey results based on Canadian data were always preferred. However, for a few nomadic species for which the majority of the population is in the United States, results at the North American level were used to reflect the population status in Canada. In these cases, the reliability of the population status was usually lowered.

If only one survey was used, the trend result for that survey equaled the final population status. If more than one survey was used, authors integrated the results to assign a population status category. The results from the most reliable survey(s) that had data going back to about 1970 carried the most weight. If the most reliable trend information did not date back to about 1970, the longest reliable results were used along with any other information that suggested change since about 1970 (e.g. results from less reliable sources or information on habitat availability or threats operating at that time). If more than one source was used, results were weighted according to their reliability. Authors used both trends and annual indices, if available. If both the trajectory of the annual index and the trend of the survey closely agreed, the trend was used to determine population status. However, if the trajectory was non-linear, authors had to use their judgment in weighing these sources of information.

Both the long-term and most recent national trends as well as annual indices (as available) are presented on the website. Although the focus of the assessment is on the longer term status (i.e. current vs. 1970), recent changes in population are also of interest because they can help indicate whether the population change is continuing, stabilizing or reversing. A recent steep decline for a long-term stable species could be of significant biological concern, whereas a recent decline in a fluctuating (cyclic or irruptive) species might be expected and would be of less concern. Regional results are displayed for some species, usually only in areas where the species’ distribution is most concentrated and/or if the regional results are reliable enough to indicate that the population change is different in a portion of the species’ range and if that difference has implications for conservation. Population status categories are:

  • Large Decrease: >= 50% decrease
  • Moderate Decrease: >= 25%, < 50% decrease
  • Little Change: < 25% decrease, <= 33% increase
  • Moderate Increase: > 33%, < 100% increase
  • Large Increase: > 100% increase
  • Data Deficient: Insufficient data to determine population status
2.2.4 Assessing reliability of population status

The overall reliability of the population status relative to about 1970 was based on an integration of individual reliabilities from the selected surveys. If only one survey was used to determine the population status, the overall reliability was equal to the reliability for that survey. If more than one survey was used to assign status, authors considered a lower value for the overall reliability if there was substantial disagreement in trend among the surveys used, or a higher value if multiple surveys were used that all pointed to the same population status.

The overall reliability category more or less matched the following definitions (based on Blancher et al. 2009):

  • High: status category is likely to be correct, or at worst within one status category of the actual species status.
  • Medium: significant uncertainty about the status category, but is likely to be within one status category of that assigned, and not incorrect by more than two status categories.
  • Low: substantial uncertainty in status, such that actual status of the species may be two status categories different than assigned, and sometimes more.
  • Data Deficient: no data, too much uncertainty in the data, or potential bias is too large to support any status category.

2.3 Population status details page

This page provides a discussion of the most reliable data source for each species, how well the species is monitored in Canada, how results were integrated if more than one data source was used, and the pattern of population change. For most species, a table of selected survey trends and, if available, graphs of annual indices are shown.

Population trends table: This table displays the annual percent change in population for the longest period of each selected survey and, when available, the most recent period. The geographic area, and range of years included in the trend, and upper and lower credible/confidence intervals are displayed. The population change is considered statistically significant if the credible/confidence interval does not include zero.

Annual Index graphs: For the BBS, CBC and shorebird migration surveys, annual index graphs show an estimate of the average number of individual birds that would be seen on a randomly selected route by an average observer. The estimate has been smoothed to account for variability in the actual routes run in a year and the observer.

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2.4 Maps

A selection of species distribution, relative abundance and migration movement maps were provided to authors including: Nature Serve range maps, BBS relative abundance and breeding distribution, maps from the Canadian Atlas of Bird Banding Atlas and the Atlas of the Breeding Birds of Ontario. NatureServe maps are displayed for all species unless the author supplied a preferred range map. Where preferable, range maps from Birds of North America Online or Sibley (used with permission of David Sibley) were used instead of NatureServe. BBS relative abundance maps are displayed for most species whose range was relatively well covered by BBS. Maps from the Atlas of the Breeding Birds of Ontario or links to other provincial atlas websites are displayed for species whose distribution is concentrated in one province. Banding Atlas maps are displayed occasionally. Background information on all maps can be viewed by selecting the map title on each species account.

2.5 Population estimate

Population estimates were supplied for the various species groups and placed into broad categories that were reviewed by Environment Canada’s Bird Technical Committees.

Landbirds - Population estimates were extracted from the 2012 version of the Partners in Flight (PIF) Population Assessment Database.

Shorebirds - Population size estimates were derived by Environment Canada experts based on Andres et al. (2012) and updated with published or unpublished information where available. For each species, the estimates include all populations breeding within Canada as well as numbers estimated to pass through Canada on migration if the breeding grounds lie outside Canada, i.e., the total number of that species estimated to use Canada. For breeding populations, these continental estimates were then converted to population estimates for Canada using relative abundances estimates when available, estimated proportion of the range in Canada or expert opinion.

Seabirds and Waterbirds - Revised population estimates of regional seabird populations were provided by Environment Canada staff in 2014 using published and unpublished information. These regional estimates were summed to determine the population estimate for Canada. For colonial-nesting species, population estimates were derived from colony counts of nests or breeding pairs conducted during the nesting season. For other waterbirds, population estimates were derived from information obtained through dedicated monitoring protocols (e.g., acoustic sampling for elusive marsh birds and counts at migratory staging areas). Final estimates were reviewed by Environment Canada’s Waterbird Technical Committee.

Waterfowl - Population estimates were extracted from the 2014 Population Status of Migratory Game Birds in Canada report (Canadian Wildlife Service Waterfowl Committee 2014). The estimates were obtained during waterfowl aerial surveys conducted mostly during the breeding season and on the staging and wintering areas.

2.6 Migration strategy/occurrence

Landbirds were assigned to a category based on their migration strategy and/or occurrence in Canada. For landbirds, migration strategy/occurrence categories were assigned largely according to Peterjohn and Sauer (1993). For a few landbirds not classified by Peterjohn and Sauer (1993), designations were added based on WildSpace (Wong et al. 2003). These were then reviewed and revised as appropriate by EC’s Landbird Technical Committee. Migration/occurrence categories for shorebirds and waterbirds were based on WildSpace with revisions made by Environment Canada. Migration/occurrence categories for waterfowl were provided by Environment Canada. In some cases it was difficult to assign a species to any one migration strategy; these species were not categorized.

Migration/occurrence categories are:

  • Resident: No significant migration; breeds and winters in the same range within Canada.
  • Short-distance migrant: Breeds in Canada and migrates to winter largely in temperate regions, e.g., southern Canada, the United States and northern Mexico or (in the case of seabirds) the boreal and temperate waters of North Atlantic and North Pacific oceans.
  • Long-distance migrant: Breeds in Canada and migrates to winter largely or completely in the south of the northern hemisphere temperate zone. For landbirds, this means in the neotropics, i.e. southern Mexico, West Indies, Central and South America.
  • Paleotropical migrant: Breeding range includes Canada but winters largely or completely in the paleotropics, i.e. Asia, Africa.
  • Seasonal visitor: Does not breed in Canada but is a regular visitor during one or more seasons. Migration strategy varies.

2.7 Canadian responsibility

Canadian responsibility scores are presented for each species. Scores were based on the percent of the world population of the species estimated to be in Canada using the ratio of Canadian population estimates to range-wide estimates. For landbirds, Canadian and world population estimates were extracted from the 2012 Partners in Flight (PIF) Population Assessment Database. For the few species without population estimates for Canada, the percent of the global breeding range in Canada was used, based on NatureServe digital range maps for the Western Hemisphere (Ridgely et al. 2007), PIF estimates of proportion of range outside of the Western Hemisphere (Blancher et al. 2007), COSEWIC or expert opinion. For shorebirds, global population estimates were extracted from WPE5 (Wetlands International 2012), and Canadian population sizes were estimated on the basis of the proportion of the range within Canada (Natureserve: Ridgely et al. 2007), or relative abundance data, where available. For seabirds, the ratio of Canadian population estimates to range-wide estimates was derived from the following sources: for loons, gulls, terns and cormorants, Delany and Scott (2006); for auks, Gaston and Jones (1998); for petrels, Brooke (2004); for gannets, BirdLife (2012); and for Pelagic Cormorant, because Delany and Scott (2006) provide only an estimate for North America, Hobson (1997). Note that some seabird species are subject to taxonomic uncertainty and estimates of Canadian responsibility could be different if a different taxonomy was adopted. World population estimates for water birds were taken mainly from Milko et al. (2003). The Canadian responsibility scores for each species were reviewed by Environment Canada staff and adjusted as necessary.

Categories used for Canadian responsibility scores are:

  • Very High: > 80% of world population estimated to be in Canada
  • High: 50 to 80% in Canada
  • Moderate: 20 to 50% in Canada
  • Low: 1 to 20% in Canada
  • Very Low: < 1% in Canada