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The Boreal Forest at Risk: A Progress Report

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PART 3: WHICH BOREAL LANDBIRD SPECIES ARE EXPERIENCING SIGNIFICANT POPULATION DECLINES?

Population trends are available for most boreal species from the North American Breeding Bird Survey. Since BBS routes are biased towards the more accessible southern portions of the boreal forest, these trends are most representative of the birds found there. Important declines in more remote parts of the boreal may be missed by BBS, as could declines in species poorly detected during BBS counts. Lists of declining species below are therefore conservative. All trend information shown below is for the longest time period available, typically in the order of 30 or more years.

There are from six to 19 species exhibiting significant declines in population, depending on region and type of trend analysis (Table 19). Some species also appear to be increasing, and there is no consistent predominance of population declines or increases across the boreal.

Table 19: Summary of Population Trends for Boreal Species, from the Breeding Bird Survey (BBS)       BBS Trend Region Years Species Restriction Declining Species* Increasing Species* # of Species Source ^     Closed Boreal Forest Stratum 1966-2001 none 11 14 105 (1)     BCR 8 (Boreal Shield) 1969-2000 none 11 6 71 (2)     BCR 6 (Boreal Taiga Plains) 1969-2000 none 15 7 93 (2)     BCR 4 (NW Interior Forest) 1985-2000 none 6 1 23 (2)     Canada 1966-2001 > 50% Canadian Pop'n in Boreal 19 23 79 (1)     Canada 1967-2000 > 50% Canadian Pop'n in Boreal 19 13 82 (2)     North America (BBS-wide) 1966-2001 > 50% North Am. Pop'n in Boreal 10 12 40 (1)     * includes species with trends different than 0 at P < 0.10     ^ Sources: (1) Sauer, J. R., J. E. Hines, and J. Fallon. 2002. The North American Breeding Bird Survey, Results and Analysis 1966 - 2001. Version 2002.1, USGS Patuxent Wildlife Research Center, Laurel, MD.   (2) Canadian Wildlife Service, Bird Trends web site   http://www.cws-scf.ec.gc.ca/cws-scf/birds/Trends/default-e.php

Table 20 shows those 40 species that are currently showing evidence of decline within the boreal forest and also at a larger geographic scale. Some of these species, like Connecticut Warbler, White-throated Sparrow and Boreal Chickadee, are principally boreal forest species, while others like Horned Lark, Western Meadowlark and Barn Swallow are typical of more southern agricultural landscapes, but are experiencing declines in the boreal as they are elsewhere.

Table 20: Boreal Canada Species with Declining Population Trends from Breeding Bird Survey (BBS)       Declining Species * Global Pop'n in Boreal BBS Population Trend ^     Closed Boreal BCR8 BCR6 BCR4 Canada1 Canada2 North Am       Neotropical Migrants                   Connecticut Warbler 92% -20.9   -2.9   -1.5 -8.9 -1.3     Mourning Warbler 75% -2.3 -2.0 -6.5   -1.2 -0.2 -0.8     Least Flycatcher 65% -1.3 1.3 -1.1   -0.9 -0.8 -1.0     Blackpoll Warbler 65% -3.8 -4.5 -11.2   -3.7 -3.7 -3.9     Canada Warbler 64% -1.2 -0.3     -1.9 -6.2 -1.9     Swainson's Thrush 59% -0.3 1.5 0.9 -7.9 -0.5 -0.5 -0.5     Clay-colored Sparrow 51%     -0.5   -1.4 -0.1 -1.2     Chestnut-sided Warbler 46% -4.1 -4.8 -0.2   -0.7 -1.6 -0.6     Olive-sided Flycatcher 38% -1.9 -3.7 3.3 -15.3 -2.9 -3.3 -3.3     Gray-cheeked Thrush 35%   -10.6       -8.8       Wilson's Warbler 31% -2.9 -0.6   -2.7 -1.6 -1.3 -1.0     Common Yellowthroat 26% -2.7 0.3 -2.0   -0.5 -0.6 -0.3     Western Wood-Pewee 19%     -3.4 -10.8 -1.1 -2.7 -1.4     Baltimore Oriole 12%     -2.2   -0.9 -0.5 -0.6     Common Nighthawk 6% 0.6   -24.6   -2.4 -7.4 -1.7     Bank Swallow 6% -11.6   -8.2   -2.1 -6.3 -0.3     Eastern Kingbird 4% -7.2   -6.7   -1.3 -1.6 -0.9     Bobolink 4% -2.8 -17.7 -0.2   -2.3 -2.8 -1.6     Barn Swallow 2% -1.0 -9.3 -4.1   -2.3 -2.8 -0.7     Short-Distance Migrants                     White-throated Sparrow 85% -0.1 -0.8 -1.1   -0.7 -0.9 -0.7     Rusty Blackbird 70% -12.4 -15.4     -10.9 -14.7 -10.7     Dark-eyed Junco 66% -1.6 2.3 0.7 -9.0 -1.6 -0.8 -1.3     White-crowned Sparrow 48%       -12.9 0.7 -1.7 -1.6     Purple Finch 47% -0.2 -1.5 -13.4   -2.2 -4.2 -1.7     Pine Siskin 46% -0.8 -3.6 0.6   -1.1 -2.6 -1.2     Belted Kingfisher 38% -5.0 2.7     -2.0 -1.4 -1.5     Northern Flicker 31% -1.2 -4.2 -4.3 -7.0 -1.1 -1.7 -2.1     Song Sparrow 20% -2.2 -3.3 -2.3   -1.1 -0.9 -0.5     American Kestrel 18% -7.1 -6.2 3.9   -1.2 0.6 -0.2     Vesper Sparrow 10% -6.8   -3.3   -0.5 -0.6 -0.9     Red-winged Blackbird 6% -1.6 -0.5 -2.2   -1.1 -1.0 -1.0     Northern Harrier 5% -5.7   -10.0   -1.4 -4.6 -0.9     Brown-headed Cowbird 5% -8.8 -15.0 -1.3   -2.3 -2.2 -1.1     European Starling 2% -1.6 -4.9 -2.1   -1.9 -2.1 -0.9     Western Meadowlark 1%     -5.5   -2.2 -1.5 -0.7     Horned Lark 1%     -15.2   -3.4 -3.3 -2.1       Resident Species                     Boreal Chickadee 78% -4.4 -6.7 1.4 -12.5 -2.9 -4.8 -2.7     Gray Jay 73% -1.3 -6.0 -6.2 -14.3 33.9 -3.4 32.0     Great Horned Owl 6%     -18.9   -1.0 -5.6 -0.2     House Sparrow <1% -8.0   -4.3   -2.6 -2.0 -2.5       * species listed here show evidence of declines within the boreal and across Canada/ North America; trends highlighted in bold are significantly different than zero at P < 0.1     ^ Trends shown are annual % decline in population, sources are as listed in Table 19: Closed Boreal, Canada1 and North Am. trends are from Sauer et al (2002), others are from CWS web site

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