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Technical Thematic Report No. 12. - Landbird trends in Canada, 1968-2006

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C. Downes, P. Blancher and B. CollinsFootnote1

Canadian Biodiversity: Ecosystem Status and Trends 2010
Technical Thematic Report No.12
Published by the Canadian Councils of Resource Ministers

Library and Archives Canada Cataloguing in Publication

Landbird trends in Canada, 1968-2006.

Issued also in French under title:
Tendances relatives aux oiseaux terrestres au Canada, de 1968 à 2006.
Electronic monograph in PDF format.
ISBN978-1-100-18651-1
Cat. no.: En14-43/12-2011E-PDF

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This report should be cited as:
Downes, C., Blancher, P. and Collins, B. 2011. Landbird trends in Canada, 1968-2006. Canadian Biodiversity: Ecosystem Status and Trends 2010, Technical Thematic Report No. 12. Canadian Councils of Resource Ministers. Ottawa, ON. x + 94 p.

© Her Majesty the Queen in Right of Canada, 2011
Aussi disponible en français

Footnotes

Footnote 1

All authors are with Environment Canada

Return to reference1

Preface

The Canadian Councils of Resource Ministers developed a Biodiversity Outcomes FrameworkFootnote1 in 2006 to focus conservation and restoration actions under the Canadian Biodiversity Strategy.Footnote2 Canadian Biodiversity: Ecosystem Status and Trends 2010Footnote3 was a first report under this framework. It assesses progress towards the framework's goal of "Healthy and Diverse Ecosystems" and the two desired conservation outcomes: i) productive, resilient, diverse ecosystems with the capacity to recover and adapt; and ii) damaged ecosystems restored.

The 22 recurring key findings that are presented in Canadian Biodiversity: Ecosystem Status and Trends 2010 emerged from synthesis and analysis of technical reports prepared as part of this project. Over 500 experts participated in the writing and review of these foundation documents. This report, Landbird trends in Canada, 1968-2006, is one of several reports prepared on the status and trends of national cross-cutting themes. It has been prepared and reviewed by experts in the field of study and reflects the views of its authors.

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Acknowledgements

Special thanks go to the thousands of volunteers throughout Canada and the United States who have participated in the North American Breeding Bird Survey, Christmas Bird Count and other monitoring programs. This paper is based on data from these programs and would not have been possible without the dedication of these highly-skilled volunteers.

We also thank the reviewers of this report.

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Ecological Classification System – Ecozones+

A slightly modified version of the Terrestrial Ecozones of Canada, described in the National Ecological Framework for Canada,Footnote4 provided the ecosystem-based units for all reports related to this project. Modifications from the original framework include: adjustments to terrestrial boundaries to reflect improvements from ground-truthing exercises; the combination of three Arctic ecozones into one; the use of two ecoprovinces – Western Interior Basin and Newfoundland Boreal; the addition of nine marine ecosystem-based units; and, the addition of the Great Lakes as a unit. This modified classification system is referred to as "ecozones+" throughout these reports to avoid confusion with the more familiar “ecozones” of the original framework.Footnote5

Ecological classification framework for the Ecosystem Status and Trends Report for Canada.

map

Long Description for Ecozones+ map of Canada

This map of Canada shows the ecological classification framework for the Ecosystem Status and Trends Report, named “ecozones+”. This map shows the distribution of 15 terrestrial ecozones+, two large lake ecozones+, and nine marine ecozones+.

Introduction and Methods

This report discusses changes in populations of landbirds in Canada from the late 1960s to the mid-2000s for species common enough to be relatively well surveyed. Landbirds are a diverse group of birds that rely primarily on terrestrial habitats for breeding and wintering. The term includes vultures, hawks, grouse, doves, cuckoos, owls, nighthawks, swifts, hummingbirds, kingfishers, woodpeckers, and passerines (or perching birds, often referred to as songbirds).

Results are presented at the national level (Canada) and for individual ecozones+ for which data were sufficient. The data used are mainly from the Canadian portion of the North American Breeding Bird Survey (BBS) (Canadian Wildlife Service, 2007; U.S. Geological Survey, Patuxent Wildlife Research Centre, 2010) but other sources are used occasionally, especially for the Arctic and taiga ecozones+. BBS results presented were analysed specifically for this report using data from between 1968 to 2006. The BBS is an avian survey conducted annually in the United States, Canada, and, starting in 2008, northern Mexico. The survey is designed to monitor trends in relative abundance of North American breeding birds at continental, national, and regional scales. The BBS focuses on landbirds and has become the main source of information on long-term population change for these species in North America. Nevertheless, the BBS does not monitor all landbird species well. Because of the timing and roadside nature of the BBS, there is generally poor coverage of most nocturnal birds, aquatic/wetland specialists, highly colonial birds, secretive and rare birds, and less than ideal coverage of early-season breeders.

Due to the remoteness and inaccessibility of the Arctic and taiga ecozones+ there are no BBS data and few other sources of data on landbirds in these regions. However, some birds that breed in northern Canada spend their winters in the United States and more southern parts of Canada and have their populations monitored by the Christmas Bird Count (CBC) (Audubon Society, 2010). In reporting on these ecozones+, we rely on trend results from the CBC provided to us by D. Niven (cf. Butcher and Niven, 2007). The CBC, now over 100 years old, monitors the status and trends of winter bird populations through an all-day, annual census conducted by groups of volunteers throughout North America. Data from the CBC complement the BBS by providing results for some species that cannot be monitored on their breeding grounds. On occasion, for some ecozones+, we also refer to results from the Atlas of the Breeding Birds of Ontario: 2001-2005(Cadman et al., 2007), the Ontario Forest Bird Monitoring Program (Cadman et al., 1998), and the Prairie Grassland Bird Monitoring Program (Dale et al., 2005).

In this report, birds are divided into species assemblages (or guilds) that share life-history traits. For the Canada-wide analysis, BBS results are presented for birds assembled by habitat, migration pattern, and foraging strategy, as well as selected individual species characteristic of each assemblage. In the ecozone+analyses, results are presented only for habitat assemblages typical of the region. Species were assigned to habitat assemblages according to Peterjohn and Sauer (1993) except for the “Other Open” assemblage that was added to capture species found in a variety of open habitats not restricted to any single habitat assemblage – that is, these birds are generalists of open habitats. Birds were assigned to foraging and migration strategy assemblages according to WILDSPACETM (Environment Canada, 2006) although some categories were grouped and other minor adjustments were made. Descriptions of species assemblages are provided in Table 1. Assemblage designations for all species included in this report are listed in Appendix 1.

Table 1. Descriptions of species assemblages.

1.1 Habitat Assemblages
HabitatDescription
ForestDeciduous, coniferous, and mixed forest habitat
Shrub/Early SuccessionalShrubland, old-field, and mid-successional stage habitat from grassland to forest
GrasslandNative grasslands (prairie and savannah habitat) and some agricultural habitat such as hayfields, pastures,
and rangeland
Other OpenOpen country (tundra excluded because of few data on these species), including species of agricultural landscapes not already assigned to the grassland assemblage
Urban/SuburbanIncludes three introduced Eurasian species (House Sparrow, European Starling, and Rock Pigeon) and native species typical of urban/suburban landscapes
1.2 Assemblages by Strategy
StrategyDescription
Year-round ResidentsNo significant migration; breed and winter in the same range within Canada
MigrationShort-distance MigrantsBreed in Canada and migrate to winter largely in temperate regions, i.e., southern Canada, the United States, and northern Mexico
Neotropical MigrantsBreed in Canada and migrate to winter largely or completely in the neotropics, i.e. southern Mexico, West Indies, Central and South America
1.3 Foraging Assemblages – by Prey Type
Prey TypeDescription
Carnivore/PiscivoreMajor food items are animals including carrion and/or fish
Herbivore/Frugivore/
Granivore
Major food items are plants including vegetation, nuts and seeds, and/orfruit
InsectivoreMajor food items are insects or other invertebrates
OmnivoreVariety of food items; includes some combination of above prey types
1.4 Foraging Assemblages – by Feeding Substrate
Feeding SubstrateDescription
AerialSpecialize in feeding on flying prey; includes “hawkers” that feed while flying, “salliers” that make forays from a perch to pursue prey; and “screeners” that fly with bills open and screen prey from the air
VegetationSelect food items from foliage, twigs, branches, and flowers
Trunk/BarkSelect food from tree trunks andunder bark
GroundSelect food from the ground

Trends were not calculated for a wetland bird assemblage because few landbirds fit cleanly into this group and because the BBS does not cover wetland habitat well. While the assemblage results presented are based on all species assigned to an assemblage for which there were BBS data, individual species results are presented only for a selection of species with reasonably good BBS trend precision (usually SE<2% per year), and which are typical of the ecozone+ as assessed by their relative abundance and proportion of their population in that ecozone+ versus elsewhere in their range. Therefore, individual species results presented do not include a comprehensive list for the ecozone+, but are a sample of birds tracked by BBS (or another source) that illustrate the range of trends ‘typical’ of the region and assemblage.

For each assemblage we present a graph of annual indices to show how populations have changed over time, an overall trend that summarizes the rate of change over the full trend period (1968 to 2006), and the relative abundance per decade for species and assemblages to illustrate how population levels change over decades. The annual index is an estimate of the average number of individual birds that would be counted on a randomly selected route by an average observer in a given year. Annual indices are shown for all species assemblages in Canada and for habitat assemblages in each ecozone+. In the tables we present a value for trend, average relative abundance per decade, and change in relative abundance. “Trend” is the annual percent change in population over the given period. Methods used to calculate trends and annual indices are described in more detail on the Canadian Bird Trends website (Collins and Downes, 2009). The 10-year relative abundances are derived from the annual indices and give the average index of abundance for that decade. “Change” is the percent change in the average index of abundance between the first decade (usually 1970s) for which we have results and the 2000s (2000 to 2006). While the overall trend gives a single measure of the rate of population change over the long-term, the annual indices and relative abundance per decade show how population levels vary within this time period.

The BBS was not established in all areas of Canada at the same time. Results for Canada overall and most of the eastern and central ecozones+ used data from 1968 onwards, while trends in several of the western ecozones+ begin in 1973, and in 1988 for the Boreal Cordillera.

Footnotes

Footnote 1

Environment Canada. 2006. Biodiversity outcomes framework for Canada. Canadian Councils of Resource Ministers. Ottawa, ON. 8 p.

Return to reference1

Footnote 2

Federal-Provincial-Territorial Biodiversity Working Group. 1995. Canadian biodiversity strategy: Canada's response to the Convention on Biological Diversity. Environment Canada, Biodiversity Convention Office. Ottawa, ON. 86 p.

Return to reference2

Footnote 3

Federal, Provincial and Territorial Governments of Canada. 2010. Canadian biodiversity: ecosystem status and trends 2010. Canadian Councils of Resource Ministers. Ottawa, ON. vi + 142 p.

Return to reference3

Footnote 4

Ecological Stratification Working Group. 1995. A national ecological framework for Canada. Agriculture and Agri-Food Canada, Research Branch, Centre for Land and Biological Resources Research and Environment Canada, State of the Environment Directorate, Ecozone Analysis Branch. Ottawa/Hull, ON. 125 p. Report and national map at 1:7 500 000 scale.

Return to reference4

Footnote 5

Rankin, R., Austin, M. and Rice, J. 2011. Ecological classification system for the ecosystem status and trends report. Canadian Biodiversity: Ecosystem Status and Trends 2010, Technical Thematic Report No. 1. Canadian Councils of Resource Ministers. Ottawa, ON.

Return to reference5

Introduction