Skip booklet index and go to page content

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

Pacific Maritime Ecozone+ (BCR 5)

Contributor: Wendy Easton

BBS routes are concentrated in the southern portion of the Pacific Maritime Ecozone+ and sample neither high elevation habitats nor forests that are inaccessible by road. Thus, trends tend to represent that part of the landscape most influenced by human settlement, more so than in other southern Canadian ecozones+. Analyses are based on the years 1973 to 2006, because there were too few BBS routes run in earlier years of the survey.

The Pacific Maritime is the only Ecozone+ in Canada in which there were statistically significant declines in all assemblages (Table 49). Birds of other open habitats showed the strongest declines with an overall loss of 61% of the population index. There are few grassland birds that have adequate trend data in this Ecozone+ so results for this group are not shown; however grassland bird populations are among those known to be at risk from habitat loss and degradation in Garry Oak ecosystems in southwestern British Columbia (for example, strigata subspecies of Horned Lark, affinis subspecies of Vesper Sparrow, and Western Meadowlarks) (Garry Oak Ecosystems Recovery Team, 2002). It is likely that many declines in other habitats are also related to habitat loss and degradation in a region with increasing human population pressure and industrial development.

Table 49. Trends in abundance of landbirds for the Pacific Maritime Ecozone+, based on data from the Breeding Bird Survey. Footnote1
Species AssemblageTrend
(%/yr)
P1970s
(BBS)
1980s
(BBS)
1990s
(BBS)
2000s
(BBS)
Change
Forest Birds-1,3 %*276,6246,6219,4197,8-29 %
Shrub/Successional-1,5 %*117,095,587,575,5-35 %
Other Open-3,4 %*61,148,132,424,0-61 %
Urban / Suburban-1,9 %*178,7197,4136,3111,2-38 %

Table 49 - 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).

Return to table 49 footnote1referrer

Top of Page

Forest bird assemblage

The forest bird assemblage has experienced a relatively steady decline over the last 33 years (Figure 40), with a loss of 29% in the overall population index (Table 49). Individual species have shown a mix of declining and nearly stable trends, with few species showing noteworthy increasing trends (Table 50). The Olive-sided Flycatcher, assessed as Threatened by COSEWIC (2007d), is declining here as it is elsewhere in Canada. The species is most abundant in western Canada but is also undergoing its strongest declines in the west, especially in the Pacific Maritime and the Montane Cordillera ecozones+.

Figure 40. Annual indices of population change in birds of forest habitat for the Pacific Maritime Ecozone+, based on data from the Breeding Bird Survey.

graphique

Long Description for figure 40

Ce graphique linéaire montre l'évolution de l'indice d'abondance annuel pour les oiseaux forestiers de l'écozone+ maritime du Pacifique, selon les données du Relevé des oiseaux nicheurs pour la période de 1973 à 2006. L'indice d'abondance montre des déclins au cours de la période, passant d'environ 300 à 200.

 

Table 50. Trends in abundance of selected species of forest birds that are characteristic of the Pacific Maritime Ecozone+, based on data from the Breeding Bird Survey. Footnote1
Forest BirdsPopulation
Trends (%/yr)
P1970s
(BBS)
1980s
(BBS)
1990s
(BBS)
2000s
(BBS)
Change
Olive-sided Flycatcher-5,5 %*3,321,840,910,79-76 %
Dark-eyed Junco-4,0 %*22,3317,0511,587,22-68 %
Rufous Hummingbird-3,5 %*8,684,033,242,87-67 %
Red-breasted Sapsucker-1,6 % 11,374,743,734,19-63 %
Golden-crowned Kinglet-1,3 % 8,224,956,094,57-44 %
Swainson's Thrush-1,2 %n54,7844,8942,5438,78-29 %
Yellow-rumped Warbler-1,2 % 10,607,427,567,35-31 %
Steller's Jay-0,4 % 4,716,495,304,53-4 %
Sooty Grouse-0,4 % 3,404,964,263,32-2 %
Varied Thrush0,1 % 16,8723,8217,9320,2220 %
Winter Wren0,2 % 17,9619,1120,2818,312 %
Warbling Vireo0,3 % 11,3811,8511,8711,390 %
Chestnut-backed Chickadee0,7 % 10,3311,4314,4911,5312 %
Townsend's Warbler0,9 % 11,3610,9510,6314,8331 %

Table 50 - 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.

Return to table 50 footnote1referrer

Top of Page

Shrub/early successional bird assemblage

Shrub/early successional birds have experienced a long-term decline in population similar to the forest birds (Figure 41), and several of these species could be considered birds of forest habitats as well. More species have declined than increased (Table 51). The Canadian population of Bewick’s Wren, now concentrated in the Pacific Maritime, shows a loss of 86% of its population since the 1970s, and has the largest population decline in this assemblage, although this species has not shown a consistent change in population at the North American level in the past 40 years (Sauer et al., 2008). The decline in the eastern and central population, where it is now largely extirpated, mainly occurred before the end of 1970s and is thus not well reflected in BBS results. The eastern decline is thought to be related to interspecific competition from expanding House Wren populations (Kennedy and White, 1997).

Figure 41. Annual indices of population change in birds of shrub/early successional habitat for the Pacific Maritime Ecozone+, based on data from the Breeding Bird Survey.

graphique

Long Description for figure 41

Ce graphique linéaire montre l'évolution de l'indice d'abondance annuel pour les oiseaux des milieux arbustifs et de début de succession de l'écozone+ maritime du Pacifique, selon les données du Relevé des oiseaux nicheurs pour la période de 1973 à 2006. L'indice d'abondance montre un déclin à long terme, passant d'environ 120 à 80 au cours de la période.

 

Table 51. Trends in abundance of selected species of shrub/early successional birds that are characteristic of the Pacific Maritime Ecozone+, based on data from the Breeding Bird Survey. Footnote1
Birds of Shrub / SuccessionTrend
(%/yr)
P1970s
(BBS)
1980s
(BBS)
1990s
(BBS)
2000s
(BBS)
Change
Bewick's Wren-7,6 %*3,443,091,090,48-86 %
Willow Flycatcher-3,8 %*8,666,104,132,93-66 %
Orange-crowned Warbler-3,8 %*19,9810,989,266,21-69 %
MacGillivray's Warbler-3,1 %*17,5716,0011,887,54-57 %
Black-throated Gray Warbler-0,7 % 1,681,982,811,18-30 %
Song Sparrow-0,2 % 16,2916,0516,2515,30-6 %
Spotted Towhee0,2 % 11,6210,7112,5011,51-1 %
Bushtit0,7 % 1,631,522,061,21-26 %

Table 51 - 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.

Return to table 51 footnote1referrer

Top of Page

Other open habitat bird assemblage

Birds of other open landscapes are declining as a group (Figure 42), a pattern repeated in all other ecozones+ except the Prairies. The overall decline of more than 50% in the last three decades (Table 49) is reflected in declines of most species. Swallow species have shown declines at varying levels. Barn Swallow and Tree Swallow have experienced the largest, statistically significant declines (Table 52), whereas the Violet-green Swallow, whose distribution is restricted to western Canada (British Columbia, Alberta, and Yukon), shows a non-significant decline in population in the Pacific Maritime. It is the only swallow not showing a negative trend at the national level, with stable trends in the Western Interior Basin and the Montane Cordillera ecozones+. Red-tailed Hawk, a common and widespread species, shows a positive trend here as well as at the national level and in most other ecozones+.

 

Figure 42. Annual indices of population change in birds of other open habitats for the Pacific Maritime Ecozone+, based on data from the Breeding Bird Survey.

graphique

Long Description for figure 42

Ce graphique linéaire montre l'évolution de l'indice d'abondance annuel pour les oiseaux des autres milieux ouverts de l'écozone+ maritime du Pacifique, selon les données du Relevé des oiseaux nicheurs pour la période de 1973 à 2006. L'indice d'abondance montre des déclins; il atteint un sommet à près de 75 en 1979, puis diminue environ à 20 dans le milieu des années 2000.

 

Table 52. Trends in abundance of selected species of birds of other open habitats that are characteristic of the Pacific Maritime Ecozone+, based on data from the Breeding Bird Survey. Footnote1
Birds of Other Open HabitatsTrend
(%/yr)
P1970s
(BBS)
1980s
(BBS)
1990s
(BBS)
2000s
(BBS)
Change
Barn Swallow-5,4 %*27,0121,9811,887,09-74 %
Brown-headed Cowbird-5,2 %*7,875,813,011,99-75 %
Tree Swallow-5,1 %*7,465,873,201,94-74 %
Brewer's Blackbird-4,3 %n11,515,633,603,46-70 %
Common Nighthawk-4,0 % 0,780,560,520,31-60 %
Savannah Sparrow-3,5 % 4,392,371,931,38-69 %
Violet-green Swallow-1,5 % 7,925,778,164,09-48 %
Red-tailed Hawk1,1 % 0,150,520,330,34119 %

Table 52 - 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.

Return to table 52 footnote1referrer

Urban and suburban bird assemblage

The declining trend in urban/suburban birds in the Pacific Maritime (Figure 43) is consistent with the rest of Canada, and as elsewhere, it is driven by large declines in introduced Eurasian species, in this case by European Starling and Rock Pigeon. The Pacific Maritime is the only region in Canada where the House Sparrow has not declined according to BBS trend data (Table 53). In contrast, Rock Pigeon trend is negative in the Pacific Maritime but stable to positive across the rest of Canada. The large, statistically significant decline in European Starling is consistent with similar declines elsewhere in Canada and in Europe (Pan-European Common Bird Monitoring Scheme, 2007).

Figure 43. Annual indices of population change in birds of urban/suburban habitat for the Pacific Maritime Ecozone+, based on data from the Breeding Bird Survey.

graphique

Long Description for figure 43

Ce graphique linéaire montre l'évolution de l'indice d'abondance annuel pour les oiseaux des milieux urbains et suburbains de l'écozone+ maritime du Pacifique, selon les données du Relevé des oiseaux nicheurs pour la période de 1973 à 2006. L'indice d'abondance montre une tendance à la baisse; il atteint un sommet en 1977 à environ 220, puis il baisse pour atteindre un peu plus de 100 en 2006.

 

Table 53. Trends in abundance of selected species of urban/suburban birds that are characteristic of the Pacific Maritime Ecozone+, based on data from the Breeding Bird Survey. Footnote1
Urban / Suburban BirdsTrend
(%/yr)
P1970s
(BBS)
1980s
(BBS)
1990s
(BBS)
2000s
(BBS)
Change
European Starling (I)-6,0 %*82,74119,5337,4416,88-80 %
Rock Pigeon (I)-3,6 % 8,337,206,123,21-61 %
American Robin-0,8 % 79,4478,5071,7763,17-20 %
House Sparrow (I)1,4 % 8,125,268,069,2414 %
House Finch2,5 % 4,127,2210,078,31102 %

Table 53 - 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; (I) indicates an introduced species; “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.

Return to table 53 footnote1referrer

Top of Page