          
DID YOU KNOW...Pine, spruce, aspen, poplar and larch trees dominate the forestlands of Canada's Boreal. |
Research & ReportsReportsThe Boreal Forest at Risk: A Progress Report« Previous Page | Table of Contents | Next Page » PART 1: HOW MANY LANDBIRDS OF HOW MANY SPECIES ARE PRODUCED IN CANADA'S BOREAL FOREST?1. b. How many individual landbirds are estimated to breed in the boreal forest?This report uses ballpark estimates, which are the best available, to illustrate major patterns of boreal breeding birds. It relies on methodology that is as consistent as possible across the boreal. This methodology also enables us to produce comparable estimates for the remainder of birds found in Canada and the United States, so that in Part 2, we can estimate the proportion of North America's birds that rely on the boreal region.5 The North American Breeding Bird Survey (BBS) and the Breeding Bird Census (BBC) are the only two standardized bird surveys that are widespread enough in Canada to allow estimation of Canada's boreal breeding population for most landbird species. These are the primary sources of data used to estimate breeding bird populations for this report.The main advantage of using BBC data is that the count procedure is intensive, and produces density estimates. Sites are not randomly assigned, but habitat data collected with the surveys can be used to extrapolate to a broader landscape. However, not all habitats have been covered well by the BBC in Canada and data collection peaked between 1965 and 1982, so most of the data are now more than two decades old.6
The North American Breeding Bird Survey routes are particularly rich in data and often contain several years of data collection per route. Coverage is good across southern Canada (see Figure 2) and the United States. The most important deficiency of the BBS is poor geographic coverage of the boreal. Most of the 221 boreal routes with usable data are located in the southern portions of the boreal, and very few are located in taiga regions. 7 Using calculations based on both sources of data, we estimate that one to three billion landbirds breed in Canada's boreal forest each year. (see Table 1).
Warblers, sparrows and thrushes are particularly abundant in the boreal forest (see Table 2). These three landbird families comprise more boreal birds than all other landbird families put together. In part this is due to the large number of warbler and sparrow species that breed in the boreal. The top 25 landbirds found in the boreal, in terms of estimated abundance, are listed in Table 3. Warblers and sparrows dominate this list too, with 10 and nine species respectively of each. The breeding population of each of the most abundant species is estimated to exceed 100 million, using both BBS and BBC data. Many of these species breed outside of the boreal forest as well. All of these species are migratory, emphasizing the seasonal nature of bird abundance in the boreal forest, and underscoring the importance of non-boreal habitats during non-breeding periods of the year.
In all of the above tables, BBC estimates tend to be higher than those based on BBS. This is at least partly because many birds present within detection distance at BBS stops are not counted, even at peak detection times of day.
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