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

Montane Cordillera Ecozone+ (BCR 10)

Contributor: Wendy Easton

BBS results in the Montane Cordillera Ecozone+ are based on data from 1973 to 2006 because too few routes were run in earlier years to include in these analyses. In this region, BBS routes tend to be concentrated in the road-accessible valley bottoms and results may not, therefore, reflect the more inaccessible areas far from roads, especially in alpine areas. The majority of the ecozone+ is forested, much of it coniferous, so representative species are mainly in the forest bird assemblage. Forest bird populations are influenced by forest practices that result in an increasingly altered and intensively managed forest landscape. Increased stand fragmentation, loss of older growth stands, alteration of natural fire regimes, and bark beetle outbreaks are some of the factors that may be contributing to forest bird declines (Canadian Intermountain Joint Venture, 2006). For migratory species, population levels will also be influenced by factors in their winter breeding grounds (southern United States and Central and South America) and along their migration corridors.

Forest and shrub/early successional bird populations have remained relatively stable in the Montane Cordillera, with the forest bird index tending slightly negative while the shrub/early successional bird index has tended upwards (Table 39). Birds of other open habitats are showing a non-significant decrease in population over the long-term. Results for the urban/suburban assemblage are not shown here although birds from this group are declining as a whole as they are throughout other regions in Canada. There are relatively few grassland birds typical of the Montane Cordillera region, therefore results are not presented for this assemblage.

Table 39. Trends in abundance of landbirds for the Montane Cordillera Ecozone+, based on data from the Breeding Bird Survey. The following table shows the BBS Abundance Index by decade from the 1970s to the 2000s.Footnote1
Species AssemblageTrend
(%/yr)
P1970s
(BBS)
1980s
(BBS)
1990s
(BBS)
2000s
(BBS)
Change
Forest Birds-0.5% 230.2251.0227.3201.6-12%
Scrub / Successional0.7%n51.453.364.857.913%
Open / Agricultural-1.8% 56.361.751.433.7-40%

Table 39 - Footnotes

Footnote 1

In this table: P is the statistical significance: * indicates P<0.05; n indicates 0.05<P<0.1; no value indicates not significant; “Change” is the percent change in the average index of abundance between the first decade for which there are results (1970s) and the 2000s (2000-2006).

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Forest bird assemblage

The overall index for the forest assemblage has been generally stable, though tending negative since the mid-1980s (Figure 32). Individual species have shown a wide range of positive, stable, and negative trends (Table 40). Several species have lost more than 50% of their population since the 1970s (Olive-sided Flycatcher, Pine Siskin, and Townsend’s Solitaire) while others such as the Red-breasted Nuthatch, Warbling Vireo, and Cassin’s Vireo, have increased by 70% or more since the 1970s. British Columbia is currently experiencing the largest recorded mountain pine beetle outbreak in North America (BC Ministry of Forests and Range, 2006). Insect infestations such as this and the subsequent forest management have profound impacts on birds. Some resident cavity-nesters that feed extensively on wood-boring beetles have increased (for example, some woodpeckers and chickadees); however, as the number of healthy trees declines, so do the species that depend on them. For example, Red-breasted Nuthatch increased early in the outbreak but has shown a recent decline (Table 40).

Figure 32. Annual indices of population change in birds of forest habitat for the Montane Cordillera Ecozone+, based on data from the Breeding Bird Survey.

graph

Long Description for Figure 32

This line graph shows the annual indices of population change in birds of forest habitat for the Montane Cordillera Ecozone+, based on data from the Breeding Bird Survey from 1973 to 2006. The overall index has been generally stable, between approximately 200 and 250, though tending negative since the mid-1980s.

 

Table 40. Trends in abundance of selected species of forest birds that are characteristic of the Montane Cordillera Ecozone+, based on data from the Breeding Bird Survey. The following table shows the BBS Abundance Index by decade from the 1970s to the 2000s.Footnote1
Forest BirdsPopulation
Trend (%/yr)
 P1970s
(BBS)
1980s
(BBS)
1990s
(BBS)
2000s
(BBS)
Change
Olive-sided Flycatcher-4.50%*5.22.81.91.2-76%
Red-eyed Vireo-4.30%*9.77.34.83.0-69%
Pine Siskin-3.82%*28.130.322.89.9-65%
Townsend's Solitaire-3.44%*1.31.10.50.4-66%
Townsend's Warbler-1.78% 2.84.02.21.9-32%
American Redstart-1.19% 9.87.27.26.8-31%
Dark-eyed Junco-1.00%n23.028.722.518.8-18%
Swainson's Thrush-0.60% 38.937.335.233.0-15%
Northern Flicker-0.30% 5.84.85.34.6-20%
Rufous Hummingbird-0.30% 1.01.21.30.8-24%
Red-naped Sapsucker-0.20% 2.02.02.21.5-27%
Yellow-rumped Warbler-0.20% 14.122.819.214.10%
Hairy Woodpecker0.00% 0.90.70.70.8-13%
Western Tanager0.30% 5.46.86.65.64%
Dusky Flycatcher0.50% 6.110.07.56.21%
Ruffed Grouse0.60% 1.30.81.31.3-3%
Golden-crowned Kinglet0.90% 3.75.25.24.214%
Ruby-crowned Kinglet1.51% 10.312.413.116.256%
Varied Thrush1.71% 3.38.37.25.466%
Hammond's Flycatcher2.12% 5.54.17.26.416%
Red-breasted Nuthatch2.22%*4.26.17.87.271%
Warbling Vireo2.74%*10.013.718.120.5106%
Cassin's Vireo4.19%*1.52.74.34.0174%
Pileated Woodpecker4.50%n0.30.90.71.0196%
Red-breasted Sapsucker8.33% 0.20.71.50.9>200%

Table 40 - Footnotes

Footnote 1

In this table: P is the statistical significance: * indicates P<0.05; n indicates 0.05<P<0.1; no value indicates not significant; “Change” is the percent change in the average index of abundance between the first decade for which there are results (1970s) and the 2000s (2000-2006). Species are listed in order from those showing most severe declines to those showing the most positive increases

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The highest abundance of Olive-sided Flycatcher, assessed as Threatened in 2007 (COSEWIC, 2007d) is found in western North America. Declines in this species have been detected in all Canadian ecozones+ for which there are trends but have been most severe in the west, where the species has lost an estimated three-quarters of its population over the last 30 years in both the Montane Cordillera and the Pacific Maritime. The species is also declining significantly in the Western Interior Basin.

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Shrub/early successional bird assemblage

The overall trend for birds in shrub/early successional habitat is stable but tending positive (Figure 33). Yellow Warbler, a riparian species, shows declines (Table 41) consistent with the other western ecozones+ (Western Interior Basin and Pacific Maritime), although its population has been stable or increasing in the rest of the country.

Figure 33. Annual indices of population change in birds of shrub/early-successional habitat for the Montane Cordillera Ecozone+, based on data from the Breeding Bird Survey.

graph

Long Description for Figure 33

This line graph shows the annual indices of population change in birds of shrub/early-successional habitat for the Montane Cordillera Ecozone+, based on data from the Breeding Bird Survey from 1973 to 2006. The abundance index shows a generally stable population, but tending positive, from approximately 45 to 60 during the period.

 

Table 41. Trends in abundance of selected species of shrub/early successional birds that are characteristic of the Montane Cordillera Ecozone+, based on data from the Breeding Bird Survey. The following table shows the BBS Abundance Index by decade from the 1970s to the 2000s.Footnote1
Birds of Shrub / SuccessionPopulation
Trend (%/yr)
 P1970s
(BBS)
1980s
(BBS)
1990s
(BBS)
2000s
(BBS)
Change
Wilson's Warbler-3.25% 6.04.63.42.2-63%
Yellow Warbler-2.27%*10.27.05.45.2-49%
Willow Flycatcher-1.19% 3.53.62.52.5-28%
Song Sparrow-0.50% 7.25.85.56.3-12%
Orange-crowned Warbler1.01% 6.78.510.48.020%
Common Yellowthroat1.92%*2.72.63.94.047%
MacGillivray's Warbler2.22%n4.89.210.69.494%
Lazuli Bunting3.25% 0.61.11.71.189%
Alder Flycatcher4.19%*1.71.94.74.2143%
Lincoln's Sparrow9.75%*0.82.57.55.5>200%

Table 41 - Footnotes

Footnote 1

In this table: P is the statistical significance: * indicates P<0.05; n indicates 0.05<P<0.1; no value indicates not significant; “Change” is the percent change in the average index of abundance between the first decade for which there are results (1970s) and the 2000s (2000-2006). Species are listed in order from those showing most severe declines to those showing the most positive increases.

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Other open habitat bird assemblage

Birds of other open landscapes are declining as a group (Figure 34), a pattern repeated in all other ecozones+ except the Prairies. Trends vary among individual species though there have been more declines than increases for the representative species listed (Table 42). This assemblage contains many of the aerial-foraging insectivores (swallows and nighthawks) that are declining as a group across Canada. The Violet-green Swallow stands out as the only swallow with a non-negative trend here and in Canada as a whole. The highest abundance of Common Nighthawk is found in the west where, in the Montane Cordillera, they have experienced a loss of two-thirds of their populations since the 1970s. The Common Nighthawk is declining across Canada, and was assessed as Threatened by COSEWIC(2007c).

Figure 34. Annual indices of population change in birds of other open habitats for the Montane Cordillera Ecozone+, based on data from the Breeding Bird Survey.

graph

Long Description for Figure 34

This line graph shows annual indices of population change in birds of other open habitats for the Montane Cordillera Ecozone+, based on data from the Breeding Bird Survey from 1973 to 2006. The abundance index shows a declining trend, ranging between 78 and 28 over the period.

 

Table 42. Trends in abundance of selected species of birds of other open habitats that are characteristic of the Montane Cordillera Ecozone+, based on data from the Breeding Bird Survey. The following table shows the BBS Abundance Index by decade from the 1970s to the 2000s.Footnote1
Birds of Other Open HabitatsPopulation
Trend (%/yr)
 P1970s
(BBS)
1980s
(BBS)
1990s
(BBS)
2000s
(BBS)
Change
Barn Swallow-4.69%*7.310.46.32.2-70%
American Kestrel-4.50%*1.11.40.80.3-70%
Common Nighthawk-3.92%n1.01.10.80.3-66%
Brewer's Blackbird-2.27% 6.58.95.54.0-38%
Tree Swallow-1.98% 9.811.49.65.7-42%
Northern Rough-winged Swallow-1.59% 4.34.83.82.6-38%
Mountain Bluebird-0.10% 1.60.91.11.4-13%
Violet-green Swallow0.20% 3.85.05.93.5-8%
Red-tailed Hawk3.36%*0.30.30.50.583%

Table 42 - Footnotes

Footnote 1

In this table: P is the statistical significance: * indicates P<0.05; n indicates 0.05<P<0.1; no value indicates not significant; “Change” is the percent change in the average index of abundance between the first decade for which there are results (1970s) and the 2000s (2000-2006). Species are listed in order from those showing most severe declines to those showing the most positive increases.

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