Boreal Birds of North America: A Hemispheric View of Their Conservation Links and Significance

Boreal Birds of North America: A Hemispheric View of Their Conservation Links and Significance

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by Jeffrey V. Wells

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Reaching from interior Alaska across Canada to Labrador and Newfoundland, North America’s boreal forest is the largest wilderness area left on the planet. It is critical habitat for billions of birds; more than 300 species regularly breed there. After the breeding season, many boreal birds migrate to seasonal habitats across the United States, Mexico, the…  See more details below


Reaching from interior Alaska across Canada to Labrador and Newfoundland, North America’s boreal forest is the largest wilderness area left on the planet. It is critical habitat for billions of birds; more than 300 species regularly breed there. After the breeding season, many boreal birds migrate to seasonal habitats across the United States, Mexico, the Caribbean, and Central and South America. This volume brings together new research on boreal bird biology and conservation. It highlights the importance of the region to the global avifauna and to the connectivity between the boreal forest and ecoregions throughout the Americas. The contributions showcase a unique set of perspectives on the migration, wintering ecology, and conservation of bird communities that are tied to the boreal forest in ways that may not have been previously considered.

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University of California Press
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Studies in Avian Biology , #41
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Boreal Birds of North America

A Hemispheric View of Their Conservation Links and Significance

By Jeffrey V. Wells


Copyright © 2011 Cooper Ornithological Society
All rights reserved.
ISBN: 978-0-520-95058-0


Boreal Forest Threats and Conservation Status

Jeffrey V. Wells

North America's boreal forest region is considered one of the most intact and least disturbed of the globe's terrestrial forested ecosystems (Lee et al. 2006). Its nearly 600 million hectares span from interior Alaska across Canada to Labrador and Newfoundland (Fig. 1.1) and encompass some of the world's largest peatlands, lakes, and rivers (Schindler and Lee 2010, Wells et al. 2011), major stores of terrestrial carbon (Carlson et al. 2009, 2010; Tarnocai et al. 2009), large populations of carnivores (Canadian Boreal Initiative 2005, Cardillo et al. 2006, Bradshaw et al. 2009), and some of the world's last remaining unchecked large mammal migrations (Wilcove 2008, Hummel and Ray 2009).

This volume highlights new research that is illuminating the importance of the region to North America's avifauna and the complexity of avian ecological connectivity between the boreal forest region and ecoregions throughout the Americas. The contributions showcase a unique set of perspectives on the migration, wintering ecology, and conservation of avifaunal communities that are tied to the boreal forest in ways that may not have been previously considered.

In North America's boreal forest, as in its Southern Hemisphere counterpart, the Amazon, development and land-use management decisions are occurring at an accelerated rate. An assessment in 1987 suggested that 26% of the "frontier forests" of North America (virtually all in the boreal forest region) were under moderate or high threat (Bryant et al. 1997). Another analysis ranked two southern boreal forest ecoregions as being in Critically Endangered condition, one as Endangered, and seven additional boreal forest ecoregions as Vulnerable (Ricketts et al. 1999)

Estimates of the amount of habitat in the southern boreal forest that is no longer intact range as high as 66% (Ricketts et al. 1999), encompassing 177 million hectares. Using satellite imagery, Lee et al. (2006) documented that less than 15% of the 71 million hectare Boreal Plains ecozone (the portion of the southern boreal extending from the eastern foothills of the Canadian Rockies to south-central Manitoba) remains in large, intact forest landscapes. Between 1990 and 2000 over 400,000 hectares of the southern boreal of Saskatchewan and Manitoba and over 2.4 million hectares of the boreal of Quebec was disturbed by human-caused influences including forestry, road-building, and other infrastructure development (Stanojevic et al. 2006a, 2006b).

Since 1975 over 31 million ha of Canadian forest have been harvested (Canadian Council of Forest Ministers 2010). Between 1990 and 2008 the total area harvested in Canada was 18,412,244 ha (Canadian Council of Forest Ministers 2010). Assuming the same rate of harvest and that 65% of the Canada's timber harvest occurs in the boreal forest region, about 6 million ha will be harvested in Canada's boreal region over the next ten years.

Many other kinds of industrial disturbances are taking place within the boreal forest region. Oil and gas exploration and extraction activities, especially in the western boreal forest region, are rapidly increasing. In Canada, a record 22,800 oil and gas wells were drilled in 2004, and the number of new wells drilled annually is projected to continue increasing (Canadian Association of Petroleum Producers 2005). The industrial footprint from oil and gas extraction activities throughout Canada's boreal forest region as of 2003 was estimated at 46 million ha, or approximately 8% of Canada's boreal forest region (Anielski and Wilson 2005). Within Alberta's oil sands region, habitat that would have supported an estimated 58,000–402,000 breeding birds has already been lost (Timoney and Lee 2009) and future losses have been projected into the tens of millions (Wells et al. 2008).

In Canada, large hydropower projects developed in the 1970s and 1980s have flooded millions of hectares (Wells et al. 2011), especially in parts of the eastern boreal forest region. For example, five reservoirs established in the La Grande River region of central Quebec flooded 1.1 million hectares of terrestrial habitat (Gauthier and Aubry 1996).

Currently, approximately 70% of bird species that regularly breed in Canada's boreal forest region show impacts from anthropogenic disturbance (road building, forestry, mining, etc.) within at least 10% of their distribution, while in only 11% of bird species is at least 10% of the range within protected areas (J. V. Wells, unpubl. data). For example, 24% of the breeding distribution of Canada Warbler (Wilsonia canadensis) in the Canadian boreal forest region is within areas impacted by anthropogenic disturbance, while 7% of its distribution is within protected areas (Fig. 1.2). In the case of the Evening Grosbeak (Coccothraustes vespertinus), 39% of its breeding distribution in Canada's boreal forest is within areas impacted by anthropogenic disturbance, while 9% is within protected areas (Fig. 1.3).

Fortunately, great strides have been and continue to be made in the conservation of North America's boreal forest. Over 45 million hectares of new protected areas have been established in Canada's boreal forest region since 2000 and 30 million hectares of forest tenures have been certified through the Forest Stewardship Council (S. Kallick, pers. comm.). The governments of Ontario and Quebec have pledged to establish another 80 million hectares of new protected areas and the federal government has continued to move forward on establishing new protected areas in the Northwest Territories that are co-managed with indigenous governments (Reid 2010). Many indigenous communities of Canada's boreal forest region have developed land-use plans that call for ambitious protected areas goals. For example, the Dehcho Land Use plan in the southern Northwest Territories calls for protecting at least 50% or nearly 11 million hectares of their lands (Charlwood and Wells 2007). In May of 2010, the Forest Products Association of Canada (FPAC) announced an agreement that it had reached with leading environmental organizations to halt logging on 29 million hectares of forestry tenures held by FPAC member companies in especially sensitive habitats while a conservation plan is developed for the total 72 million acres of forestry tenures that they control (Kallick 2010, Pew Environment Group 2010).


Global Role for Sustaining Bird Populations

Jeffrey V. Wells and Peter J. Blancher

Abstract. Spanning 5.9 million square km, the boreal region of North America stretches from Alaska to Newfoundland, and represents 25% of the earth's remaining intact forests. As one of the largest wilderness areas left on the globe, the boreal forest hosts a diverse and unique avian assemblage that is a valuable component of global biodiversity. We endeavor to quantify its importance to the maintenance of North American bird populations. We used a simple modeling approach to develop an assessment of the conservation value of North America's boreal region for birds and provide one of the first attempts to quantitatively describe the stewardship responsibility of a global-scale ecosystem. Results illustrate that the boreal region is critical to the well-being of many bird species. We found that nearly half (325) of all regularly occurring North American bird species occur regularly within the boreal region and that over 300 species regularly breed there. In at least 96 species, 50% or more of their entire breeding population was estimated to occur within the boreal region. The boreal region of North America represents a unique global conservation asset for birds and other forms of biodiversity that should be protected.

Key Words: Alaska, boreal forest, biodiversity, bird conservation, Canada, conservation assessment, conservation value.

Global-level conservation assessments have historically focused on measures of species diversity or rarity in the form of endemism or endangerment. Under such schemes, areas with high diversity and/or high numbers of endemic or endangered species have higher conservation value (Margules and Pressey 2000, Karieva and Marvier 2003, Cardillo et al. 2006, Ceballos and Ehrlich 2006, Lamoreux et al. 2006). Global-scale assessments that have used diversity and rarity-based approaches generally find that, as expected, tropical and subtropical regions of the world have the highest diversity and highest numbers of endemic and endangered species (Myers et al. 2000, Hoekstra et al. 2005, Wilson et al. 2006). In fact, diversity and rarity are but two of many conservation values that can be considered. For example, ecosystem function, ecosystem services, intactness of habitat, and species abundance have begun to be recognized as equally important factors to consider in developing conservation priorities (Costanza et al. 1997, Ricketts et al. 1999, Karieva and Marvier 2003, Mittermeier et al. 2003, Ceballos and Ehrlich 2006, Chan et al. 2006, Leroux and Schmiegelow 2007).

Conservation assessments based on diversity and rarity have been vastly important in raising awareness of the need for urgent conservation action to prevent the imminent extinction of many species and the loss of the last remnants of some of earth's most species-rich ecological communities. One consequence of such prioritization schemes, however, is that the conservation values and priorities of regions ranked relatively low in conservation priority are unclear. For example, a comparison of the bird species diversity of Ontario with that of Peru—two jurisdictions of roughly similar size—shows that Peru has vastly greater species diversity (1,800 spp versus 500 spp). Not surprisingly, though, the Ontario government will not spend the bulk of its taxpayer monies on biodiversity protection in Peru despite the fact that Peru has more species. That is because most national and provincial or state governments and nonprofit organizations are given mandates to protect and manage species within their geographic boundaries. In this example, the Ontario government, rather than comparing its species diversity to that of another country, would be better served to understand and enumerate the conservation values that make it globally unique.

One measure of conservation value that has only recently been given explicit consideration in conservation planning is that of abundance. Through its Important Bird Areas program, BirdLife International was one of the first organizations to explicitly consider both abundance and rarity in conservation decision-making (Wells 1998, Heath and Evans 2000, Fishpool and Evans 2001, Chipley et al. 2003, Wells et al. 2005). More recently, the Partners in Flight coalition and its members have highlighted the concept that some regions have a high stewardship responsibility for maintaining species that are still abundant (Rosenberg and Wells 1995, 2000, 2005; Wells and Rosenberg 1999; Rich et al. 2004).

In this paper, we provide an assessment of the value of North America's boreal region in supporting and maintaining continental bird populations. We consider the taxonomic diversity supported by the boreal region at the family and species level, the total numbers of birds of each species that breed in the boreal region, and the use of the boreal region by birds during migration.


The boreal forest of North America, stretching from Alaska across 6,000 km to Newfoundland, is, at 5.9 million square km, the largest wilderness left in North America and represents 25% of the world's remaining intact forests (Canadian Boreal Institute 2005). Although there are many delineations of the boreal zone that differ slightly in the mapping of the southern and/or northern border, for these analyses we defined the boreal region as the area within Bird Conservation Regions 4, 6, 7, and 8 (Fig. 2.1; U.S. NABCI Committee 2000).

Distribution maps of all North American birds (Ridgely et al. 2003) were overlaid with boundaries of Bird Conservation Regions (BCRs) and the proportion of the breeding, migration, and wintering range of each species that occurred within the boreal region was calculated using ArcINFO. An implicit assumption in the use of distribution maps is that a region's importance to a species is strongly related to the proportion of that species' range in the region. This assumption is reasonable for most species, but may break down for species with highly clumped distributions, such as breeding seabirds and other colonial waterbirds. For these species, use of colony counts if available across a species range would provide a more accurate assessment of relative importance of the boreal region. North American Breeding Bird Survey (BBS) data from 1990 to 1999 were used to provide an alternative measure of the proportion of breeding birds of each species in the boreal region using methods outlined in Rosenberg and Wells (1995, 2000). We calculated a mean relative abundance for each species within portions of each BCR that occurred within a province or state. A correction factor was applied to each mean value to account for differences in detectability and time of day and to correct for male-biased detection of singing birds, as described in Rich et al. (2004). Each adjusted mean abundance value was divided by the estimated area of detectability to obtain an estimate of density, and this value was multiplied by the area of each provincial/ state BCR polygon to obtain an estimated total abundance for that polygon. Total abundance for each species within each polygon was summed across all polygons where the species occurred to get a North American total population size. Abundance estimates from the four boreal BCRs were summed and the percent of total North American population size was calculated for each species.

BBS relative abundance estimates in the boreal region were based on a reasonably high number of individual survey routes (265). However, the distribution of routes is biased toward the southern parts of the boreal. Routes were stratified by province/state/territory and BCR to minimize effects of this bias, but low sample size in the northern parts of the boreal results in low precision in estimates of bird numbers for many species. Some species, particularly many nonlandbirds, were not sampled well by BBS surveys. For this reason, estimates of population sizes of shorebirds, waterfowl, and waterbirds relied on continental estimates provided in continental plans (Donaldson et al. 2000 and Brown et al. 2001 for shorebirds, Kushlan et al. 2002 and Milko et al. 2003 for waterbirds, and NAWMP 2004 for waterfowl). Continental estimates were multiplied by proportions of range or proportions of BBS population in the boreal to give an approximate estimate of breeding population size in the boreal. For waterfowl in particular, a more accurate estimate of the proportion of continental populations that occur in the boreal should be possible with the use of various waterfowl survey data sets, not treated in this paper (but see Chapter 3).

Proportions of western hemisphere population for all birds were based on a combination of BBS proportions within the BBS survey area and proportion of breeding range elsewhere in the hemisphere.


Taxonomic Diversity

Nearly 400 species (399, or 57% of regularly occurring birds of the U.S. and Canada) are known to occur within some portion of the boreal forest region of Alaska and Canada. Excluding species that are exclusively marine or coastal or that occur in less than 1% of the boreal region, there remain 325 species (47%) (Appendix 2.1—see this appendix for all scientific names of species mentioned in text). A total of 304 species (43%) breed in the forests, thickets, and wetlands of the boreal forest. The remaining 21 species occur as migrants or winterers within the region.

At least 47 families of birds are represented, making up 67% of all bird families that regularly occur in the U.S. and Canada. Certain families have an especially high representation in the boreal. Thirty-five of 44 waterfowl species (80%) that nest in the U.S. or Canada are boreal forest breeders, at least in part. Fifty-three percent (27 of 51) of warblers, 63% of finches, and 93% (13 of 14) thrushes that nest in the U.S. and Canada are boreal breeders.


Excerpted from Boreal Birds of North America by Jeffrey V. Wells. Copyright © 2011 Cooper Ornithological Society. Excerpted by permission of UNIVERSITY OF CALIFORNIA PRESS.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
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Meet the Author

Jeffrey V. Wells is Science and Policy Director of the Boreal Songbird Initiative and a Cornell University Visiting Fellow. He is the author of Birder’s Conservation Handbook, Birds of Sapsucker Woods, and Important Bird Areas in New York State.

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