Technical Thematic Report No. 12. - Landbird trends in Canada, 1968-2006
Taiga Ecozones+ (Taiga Shield, Taiga Plains, and Taiga Cordillera)
There are very few data on landbird population trends in the three taiga ecozones+. Because of the remote character of these regions, the lack of roads and low population base, there are only a few scattered BBS routes and few other sources of population data. Some birds that breed in these remote northern landscapes spend their winters in the United States and more southerly parts of Canada, where their populations can be monitored by the Christmas Bird Count (CBC) (Audubon Society, 2010).
Species discussed in this section are those whose breeding range includes portions of the three taiga ecozones+. The CBC results presented below are preliminary findings based on CBC data from Canada and the United States combined (cf. Butcher and Niven, 2007). Canada has a high stewardship responsibility for all of these species because a large proportion of their breeding population is in Canada. The Rusty Blackbird, a COSEWICspecies of Special Concern (COSEWIC, 2006b) is listed, along with Smith’s Longspur, as one of 100 species on the Partners in Flight North American Watch List (Rich et al., 2004).
CBC results for North America show a mix of declining and stable population trends (Table 57). Three of the six species show consistent, statistically significant long-term declines in population.
|Rusty Blackbird||Hudson Bay|
|Boreal Chickadee||Taiga and boreal||-1.73%||*||1.6||1.3||1.2||1.2||-29%|
|Pine Grosbeak||Taiga and boreal||-0.78%||5.1||3.4||2.8||2.5||-52%|
|Lincoln's Sparrow||Taiga and boreal||-0.08%||1.5||1.5||1.7||1.6||8%|
Table 57 - Footnotes
- Footnote 1
In this table: P is the statistical significance; Asterisks (*) indicate statistically significant trends (P<0.05); 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). Data table shows the annual rate of change and the average CBC abundance index by decade.
Source: based on data from the Christmas Bird Count by Butcher and Niven (2007)
The Rusty Blackbird, a temperate migrant that winters in the United States, shows a dramatic 78% loss of population between the 1970s and the 2000s (Figure 46). This decline is supported by BBS results from other parts of its range which show an even steeper rate of decline for Canada overall (-9.9% per year), with the decline being consistent across ecozones+. However, this species is not monitored adequately by the BBSbecause its wetland forest habitat is poorly sampled by BBS routes. There is circumstantial evidence that the declines have not been as dramatic in the North, recently supported by observations made by (Machtans et al., 2007). The declines in Boreal Chickadee and Pine Grosbeak are supported by BBS declines at the southern edge of their breeding ranges (-3.2 and -6.2% per year, respectively, for Canada).
Figure 46. Trend in annual abundance index for the Rusty Blackbird, 1996 to 2005, based on Christmas Bird Count results for North America.
Long Description for Figure 46
This line graph shows the trend in annual abundance index for the Rusty Blackbird from 1996 to 2005, based on Christmas Bird Count results for North America. Populations show dramatic loss between the 1970s and the 2000s, from approximately 2.7 to 0.3 over the period.
Two species, Lincoln’s Sparrow (Figure 47) and Smith’s Longspur, show no strong change in overall population trend over the past 40 years, though the latter is difficult to monitor and change might not be detectable. The stable trend for Lincoln’s Sparrow contrasts somewhat with the more positive trends from the BBS (3.0% per year for Canada). The BBS is run along roadsides and maintenance of wide road verges in the North may benefit this species locally. They may consequently be over-represented in BBScounts (C. Machtans, Environment Canada, pers. comm., 2010).
Figure 47. Trend in annual abundance index for Lincoln’s Sparrow, 1996 to 2005, based on Christmas Bird Count results for North America.
Long Description for Figure 47
This line graph shows the trend in annual abundance index for Lincoln’s Sparrow from 1996 to 2005, based on Christmas Bird Count results for North America. Over the past 40 years no strong population trend is clear. The abundance index fluctuates between 1.2 and 2.2 over the period.
- Date Modified: