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2008 Forest Songbird and Woodpecker Monitoring in the Fort Nelson Forest District
Final Report Submitted to:
Canadian Forest Products Ltd. – Peace Liard Woodlands RR#1, Site 13, Compartment 2 Fort St. John, B.C., V1J 4M6
Attention: Darrell Regimbald [email protected]
Submitted by:
Manning, Cooper, and Associates Ltd. – Northwest Office P.O. Box 39, South Hazelton, B.C., V0J 2R0
Tel: 250.842.5779 Contact: Karl Bachmann [email protected]
January 31, 2009
Erin O’Brien
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EXECUTIVE SUMMARY Recognizing the potential negative impacts of forest harvesting on some aspects of biological diversity, Canadian Forest Products Ltd. has developed a Sustainable Forest Management plan to preserve biological integrity within their operational areas. This management plan uses a series of ecological indicators to assess the effectiveness of forest management practices in maintaining biological diversity. Such indicators include groups of species that have unique habitat associations, and their presence or absence can be used to determine how well the range of natural variation in habitat types is represented across a landscape. In this study, we collect information on songbird and woodpecker populations in the Fort Nelson Forest District and highlight species that represent a range of habitat types and thus may be used as ecological indicators. This year’s report, as part of a multi-year research project, expands upon the previous years of data collection, providing an additional year of baseline information on songbird richness, abundance and distribution, allowing for a refined analysis of habitat associations for individual species. Certain species in the study area were strongly associated with particular habitat types and would lend themselves well to future monitoring efforts. Of particular interest was the Ovenbird, which may act as a good indicator of mature, hardwood-dominated stands. Because future harvesting efforts are likely to target this habitat type, we recommend that these species be monitored for long-term population changes. Furthermore, we suggest that management plans should provide for retention of large patches of mid- to mature hardwood forest, and minimize fragmentation in this habitat type.
ACKNOWLEDGEMENTS Darrell Regimbald, Canadian Forest Products Ltd., provided logistical support during the set-up and reporting phases of this project. Funding was provided by the British Columbia Forest Investment Account (FIA) administered by Canfor Ltd in the Fort Nelson Operating Area. Field biologists Karl Bachmann, Pierre-Paul Bitton, Kevan Cowcill, Nathan Hentze, and Michael Shepard completed the songbird surveys. Brooke Eschuk completed all GIS analyses. This report was written by Karl Bachmann, Pierre-Paul Bitton and Nathan Hentze. Todd Manning, Mike Shepard and John Cooper provided reviews of the manuscript. Cover Photo: Mike Yip.
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TABLE OF CONTENTS EXECUTIVE SUMMARY .............................................................................................. ii ACKNOWLEDGEMENTS .............................................................................................. i TABLE OF CONTENTS ................................................................................................. 2 LIST OF FIGURES .......................................................................................................... 3 LIST OF TABLES ............................................................................................................ 4 LIST OF APPENDICES .................................................................................................. 5 1. INTRODUCTION..................................................................................................... 6
1.1 Ecological Context.......................................................................................... 6 1.2 Management Context ...................................................................................... 6 1.3 Project Objectives ........................................................................................... 7
2. STUDY AREA........................................................................................................... 8 2.1 Study Area ...................................................................................................... 8 2.2 Biogeoclimatic Ecological Classification ..................................................... 10
3. METHODS .............................................................................................................. 11 3.1 Point Count Surveys ..................................................................................... 11 3.2 Mapping Bird Detections with GIS .............................................................. 13 3.3 Habitat Classification.................................................................................... 13 3.4 Data Analysis ................................................................................................ 14
4. RESULTS ................................................................................................................ 14 4.1 Survey Effort................................................................................................. 14 4.2 Abundance and Diversity.............................................................................. 15 4.3 Habitat........................................................................................................... 18 4.4 Species at Risk .............................................................................................. 20 4.5 Habitat Associations ..................................................................................... 21 4.6 Woodpeckers................................................................................................. 26 4.7 Stand Level Surveys ..................................................................................... 28
5. DISCUSSION .......................................................................................................... 29 5.1 Habitat Classification.................................................................................... 29 5.2 Songbird Habitat Relationships .................................................................... 29 5.3 Woodpecker – Habitat Relationships............................................................ 30 5.4 Songbirds in Interior Forest Stands .............................................................. 31 5.5 Species at Risk .............................................................................................. 32 5.6 Implications for Forest Management ............................................................ 32
6. REFERENCES........................................................................................................ 34
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LIST OF FIGURES Figure 1. The Fort Nelson Forest District (as indicated in green, Ministry of Forests website). .............................................................................................................................. 8 Figure 2. Distribution of roadside point count stations (in red) and stand level point count stations (in blue) in the Fort Nelson Forest District............................................................ 9 Figure 3. Roadside point count station (B-10B-28) in the Fort Nelson Forest District.... 11 Figure 4. Stand-level point count station (B-10B-0O) in the Fort Nelson Forest District.12 Figure 5. Proportion of the study area as a function of stand classification (HW = Hardwood; SW = Softwood; MW = Mixedwood; CB = Cutblock) and age class in the Fort Nelson Forest District, Spring 2008.......................................................................... 20 Figure 6. Density of White-throated Sparrow (WTSP) in relation to habitat types (HW = Hardwood; SW = Softwood; MW = Mixedwood; CB = cutblock) in the Fort Nelson Forest District, Spring 2008.............................................................................................. 25 Figure 7. Density of American Redstart (AMRE) in relation to habitat types (HW = Hardwood; SW = Softwood; MW = Mixedwood; CB = cutblock) in the Fort Nelson Forest District, Spring 2008.............................................................................................. 25 Figure 8. Density of Warbling Vireo (WAVI) in relation to habitat types (HW = Hardwood; SW = Softwood; MW = Mixedwood; CB = cutblock) in the Fort Nelson Forest District, Spring 2008.............................................................................................. 26 Figure 9. Density of Yellow-bellied Sapsucker (YBSA), Pileated Woodpecker (PIWO), and Northern Flicker (NOFL) in relation to habitat types (HW = Hardwood; SW = Softwood; MW = Mixedwood; CB = cutblock) in the Fort Nelson Forest District, Spring 2008................................................................................................................................... 28
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LIST OF TABLES Table 1. Biogeoclimatic zones and variants in the Fort Nelson Forest District. ............. 10 Table 2. Songbird species detected in the Fort Nelson Forest District in 2008, with total number of detections. Species for which a detailed habitat analysis was conducted are indicated in bold................................................................................................................ 15 Table 3. Songbird and woodpecker species richness, total numbers and average numbers detected per point (road side + stand level) for transects surveyed in the Fort Nelson Forest District, Spring 2008.............................................................................................. 17 Table 4. Proportion of transects (expressed as a percentage of total area surveyed) categorized by stand classification and seral stage, Fort Nelson Forest District, Spring 2008................................................................................................................................... 19 Table 5. Red-listed (threatened or endangered), blue-listed (special concern), or COSEWIC designated species detected during roadside and stand-level point counts, 2008................................................................................................................................... 21 Table 6. Relative proportion of the 20 most abundant birds (expressed as a percentage) detected in different seral stages and stand classifications (including road-side and stand-level stations) in the Fort Nelson Forest District, spring 2008. ........................................ 22 Table 7. Relative proportion of the 20 most abundant birds (expressed as a percentage) detected in by seral stage in the Fort Nelson Forest District, Spring 2008. Values do not add to 100 since Non-forested and Cutblock areas were not included. ............................ 23 Table 8. Results from generalized linear models including stand classification, stand age, canopy closure, and transect as predictors of bird density (birds/ha) in the Fort Nelson Forest District, Spring 2008.............................................................................................. 24 Table 9. Woodpecker species detected in the Fort Nelson Forest District, Spring 2008. Scientific names, four-letter code, and number of detections are shown. ........................ 27 Table 10. Relative proportion of woodpeckers (expressed as a percentage) detected in different seral stages and stand classifications in the Fort Nelson Forest District, Spring 2008................................................................................................................................... 27
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LIST OF APPENDICES Appendix 1. Example of orthophoto with point count detections in the Fort Nelson Forest District, 2008.......................................................................................................... 40 Appendix 2. Non-target species (i.e., species other than songbirds and woodpeckers) detected in the Fort Nelson Forest District, Spring 2008. Scientific names, four-letter code, and number of detections are shown. ...................................................................... 41
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1. INTRODUCTION
1.1 Ecological Context As a result of its complex topography, hydrology, and climatic patterns, British Columbia is host to a diverse array of plants and animals, contributing significantly to the overall biological diversity of Canada. The northeastern corner of the province, characterized by a continental climate with short, warm summers, and long, cold winters, forms the western portion of the boreal forest (Meidinger and Pojar 1991). Despite the increased focus of ecological research and conservation efforts in Canada’s boreal forests, there remains a paucity of information on birds, the most abundant vertebrate group in the region (Mönkkönen and Viro 1997). Large areas of Canada’s boreal forest are currently being managed for timber production, and the effects of the resulting large-scale habitat fragmentation on breeding birds are largely unknown. The loss of breeding habitat in North America has been hypothesized as a major cause of declines in migratory songbird populations (Wilcove 1985, Böhning-Gaese et al. 1993); however, exactly how songbirds respond to fragmentation seems to be highly system and species-specific (Donovan and Flather 2002, Shmiegelow and Mönkkönen 2002). Monitoring songbirds and collecting baseline data on songbird populations in managed forest landscapes complements and informs regional and national conservation efforts (Fitzgerald et al. 2006).
1.2 Management Context Forest harvesting has the potential to negatively impact biodiversity by altering habitat crucial to many species (e.g., Spies et al. 1988). In recognition of this, Canadian Forest Products Ltd.’s (Canfor) Fort Nelson Division has developed a Sustainable Forest Management (SFM) plan that uses a Criteria and Indicator framework to achieve sustainable forest management (Canfor 2004, Canfor and BCTS 2005). Criterion 1 of this plan addresses the maintenance of biodiversity by stating that “Biological richness and its associated values are sustained in the Defined Forest Area (DFA)”. Associated with this criterion are three ecologically-focused indicators:
1. Ecologically distinct habitat types are represented in an unmanaged state in the DFA to sustain lesser known species and ecological functions.
2. The amount, distribution, and heterogeneity of terrestrial and aquatic habitat elements and structures important to sustain biological richness are maintained.
3. Productive populations of selected species or species guilds are well distributed through the range of their habitat.
Practical application of these indicators in a forest management context suggests that they provide a useful framework to guide efforts to conserve biodiversity (e.g., Bunnell et al. 2003). Indicators one and two use ecosystem representation and habitat structure as surrogate indices for species. Indicator three assesses the success of indicators one and
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two in sustaining species by monitoring trends for species or groups of species (Bunnell et al. 2003). Species or groups of species must therefore be chosen for focal monitoring efforts. Bunnell (2005) has developed a species accounting system that has two major goals: (1) account for presence of species across the defined forest area, and (2) identify uncertainties in assigning species presence and directing effectiveness monitoring to where it is most needed. It integrates indicators two and three by linking indices of biodiversity (habitat elements) with the species themselves. Under the species accounting system, species are classified into 6 monitoring classes:
1. generalists, species that can occupy many different forest types 2. species that can be linked to broad habitat types 3. species linked to specific habitat elements 4. species that use specific or localized habitats 5. species linked to landscape features 6. species not associated with forested habitats
Once species have been assigned to specific classes, focal species that respond to forest practices can be selected for monitoring (Bunnell and Vernier 2007). Species grouped into classes two and three are best suited for large-scale monitoring to assess the potential impacts of forest management activities. Species chosen for monitoring should meet the following criteria: (1) be forest dwelling, (2) be sensitive to forest practices employed, (3) be practical to monitor in terms of sampling, identification, and cost, and (4) provide information useful in guiding forest practices (Bunnell et al. 2003). Due to the tendency of songbirds to respond numerically to changes in their environment, this group is ideally suited as ecological indicators in studies of environmental change (Robbins et al. 1986, Canterbury et al. 2000, O’Connell et al. 2000, Carignan and Villard 2002). Songbirds consistently show habitat preferences depending on the species, and models of focal species with particularly strong habitat associations can be applied to forest management practices in order to preserve the range of ecological variability necessary to sustain the full bird community (Crozier and Niemi 2003, Rempel 2007).
1.3 Project Objectives This project addresses measures 1-3.1 (recommend vertebrate species for monitoring) and 1-3.2 (vertebrate populations remain productive relative to baseline) under indicator 1-3 of Canfor’s Fort Nelson division SFM plan (Canfor and BCTS 2005). The long-term objective of this project is to support the species accounting system by:
1. establishing baseline data and trend information (as data allow) on forest songbird populations.
2. refining relationships of forest songbird occurrence with broad habitat classes.
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3. permitting validation and refinement of the assignment of forest songbird species to the 6 monitoring classes.
In this report, we present the third year of data in an ongoing monitoring program of songbird and woodpecker species across the Fort Nelson Forest District. The results of a third year of roadside point-count surveys along established transects and the establishment of new survey stations in interior mature-forest stands are presented. Species-habitat associations are evaluated, and potential focal species for monitoring purposes suggested.
2. STUDY AREA
2.1 Study Area The Forest Nelson Forest District (FNFD) is located in northeastern British Columbia (Figure 1), and is 9.8 million ha (98 681 km2) in area. An extensive lowland plain occurs in the eastern portion of the FNFD, bounded by mountains and associated foothills running approximately north-south in the western portion. The majority of the transects in this project were established in the eastern portion of the forest district (Figure 2).
Figure 1. The Fort Nelson Forest District (as indicated in green, Ministry of Forests website).
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Figure 2. Distribution of roadside point count stations (in red) and stand level point count stations (in blue) in the Fort Nelson Forest District.
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2.2 Biogeoclimatic Ecological Classification Three different Biogeoclimatic Ecological Classification (BEC) zones occur within the Fort Nelson Forest District (Meidinger and Pojar 1991). The majority of the area consists of Boreal White and Black Spruce (BWBS, 68%) with areas of Spruce Willow Birch (SWB, 19%) and Alpine Tundra (AT, 13%) (Fort Nelson LRMP 1997). The homogeneity in topography and climate, relative to other areas of this size, results in fewer BEC Variants (Table 1).
Table 1. Biogeoclimatic zones and variants in the Fort Nelson Forest District.
BEC VARIANT
AREA (HA.)
% FORESTED AREA OF THE
FNFD ATun 892098.8 9.04%
BWBSdk1 170139.4 1.72% BWBSdk2 950682 9.63% BWBSmw2 5613561 56.89% BWBSwk2 154.1758 0.00% BWBSwk3 146594.3 1.49%
SWBmk 1773919 17.98% SWBmks 320919.4 3.25%
Grand Total 9868068 100.00%
The BWBS is the most widespread zone in Canada, generally occurring from 600 m up to approximately 1200 m. In some of the lowlands and deep river gorges in the FNFD, however, this zone can extend down to 450 m. Summers are generally warm and short, with long, cold winters and short growing seasons. Stands range from open lodgepole pine (Pinus contorta var. latifolia) stands on dry sites to black spruce (Picea mariana) stands in poorly drained areas. The dominant tree species are white spruce (Picea glauca), trembling aspen (Populus tremuloides), lodgepole pine, black spruce, tamarack (Larix laracina), sub-alpine fir (Abies lasiocarpa) and paper birch (Betula papyrifera) (Meidinger and Pojar 1991). The SWB usually occupies the altitudinal zone above the BWBS, ranging from 1000 m up to 1700 m in the northern portion of the zone. Because it is a sub-alpine zone, summers are short and cool with long, cold winters. Where forest does occur in this zone at lower elevations, it tends to be dominated by white spruce and sub-alpine fir. Upper elevations and colder low elevation sites are dominated by tall deciduous shrubs, mainly willow (Salix spp.) and scrub birch (Betula glandulosa). The AT zone occurs above the SWB zone, usually from 1400 m and up. It is usually treeless except for small krummholz forms, and is characterized by colder temperatures year round (Meidinger and Pojar 1991).
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3. METHODS
3.1 Point Count Surveys Most point count surveys were conducted along road transects; however, we conducted a sub-set of stand-level surveys in the forest interior (Figure 3, Figure 4). We surveyed 21 road transects (each having between 15 and 30 point count stations), totalling 592 point count stations, as well as 71 stand level point count stations. Stand level survey stations were situated in interior forest areas and were focused in late successional (>90 years of age) forest types. We chose interior forest sites that were a minimum of 200 m from harvested edges and 400 m from the next nearest plot centre. In order to aid observer access, stand level stations were established relatively close to accessible forest roads.
Figure 3. Roadside point count station (B-10B-28) in the Fort Nelson Forest District.
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Figure 4. Stand-level point count station (B-10B-0O) in the Fort Nelson Forest District.
Point count surveys were conducted according to methods established by the North American Breeding Bird Survey (BBS) (Sauer et al. 2004) and the provincial Forest and Grassland Bird Inventory standards (RISC 1999). Surveys were conducted between 4 June and 19 June within a four hour period commencing at sunrise. Point count surveys lasted five minutes and all bird detections were recorded onto a site-specific tally sheet. Each survey station encompassed approximately 12.56 hectares. Tally sheets contained orthophotos overlaid with radius markings of 50 m, 100 m, 150 m and 200 m derived from UTM coordinates (see example orthophoto, Appendix 1). Birds detected were placed into distance categories as follows: 1 = 0-50 m; 2 = 51-100 m; 3 = 101-150 m; 4 = 151-200 m. The use of orthophotos that included major landscape features such as roads and waterways enabled the observer to more accurately estimate the exact location of each bird detected. Each bird was given a code for how it was detected, whether it was singing, calling, visually detected, or a combination of these. Standard four-letter codes were used to indicate bird species (Preston et al. 2005). When a bird was detected, the observer indicated whether each bird was detected within the first 3 minutes of the point count, or between 3-5 minutes in order to have the data consistent with both RISC standards (5 minutes) and BBS standards (3 minutes). Any relevant additional information regarding detected birds, such as nest site locations, was noted, and birds that flew over the observer were coded as “fly-over”.
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Environmental conditions including time, percent cloud cover, ceiling height, wind speed (Beaufort scale), precipitation, and temperature were recorded at the beginning of each point count. In order to reflect the generally cool, wet spring in northern BC, point count surveys were conducted according to ‘modified’ RISC standards for environmental conditions (RISC 1999). These standards are as follows: wind speed ≤ Beaufort 3 (gentle breeze, leaves and twigs constantly move), precipitation = ‘very’ light rain, temperature > 3˚C.
3.2 Mapping Bird Detections with GIS All bird detections as recorded on orthophoto tally sheets were mapped using ArcMap 9.3 (ESRI, Redlands, CA). Associated survey data (date, observer, distance class, how detected etc.) for each observation were entered into an attribute table and linked to their respective bird observation. Detections of multiple birds (e.g., in a flock) were entered as a single record in the GIS layer.
3.3 Habitat Classification We obtained habitat data corresponding with point count stations from Vegetation Resource Inventory (VRI) data supplied by the British Columbia Ministry of Forests and Range. In the VRI database, the forested landscape is divided into polygons and information such as percent cover by tree species, age, and percent canopy closure has been estimated for each polygon based on aerial photo interpretation and ground sampling. Using GIS, we assigned each bird detection to a VRI polygon and its corresponding suite of habitat data. Additional GIS layers, including the distribution of recent harvests, roads, and road right-of-ways across the study area, were joined to a bird detection .shp file. In addition, we calculated the area of each VRI polygon that fell within the 200 m radius of each point-count survey station. We classified VRI polygons as softwood, hardwood, mixedwood, cutblock, or non-forested based on original VRI data. Forested polygons with 70% cover or more of softwood species (i.e., conifers) were classified as “softwood”, whereas polygons with 31-69% cover of softwood (the remaining proportion cover being hardwood) were classified as “mixedwood”. Forested polygons with greater than 70% cover of hardwood species (i.e., broadleaf deciduous) were classified as “hardwood”. Non-forested polygons were those characterized as non-productive forests, waterways (lakes, rivers, and wetlands), meadows, rock, and gravel pits. Polygons were further classified by age using the VRI data. Stands were classified as “early seral” if stand age was less than 30 years, “mid seral” for stands 31-90 years of age, and “late seral” for stands greater than 90 years old.
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3.4 Data Analysis Prior to beginning analyses of the point count data, all non-songbirds (e.g., grouse, raptors, shorebirds, waterfowl) were excluded from the dataset (see Appendix 2 for complete list of species excluded from analyses). Data was initially summarized as total number of detections, percent of total detections, and species richness for each transect. A detection was defined as one observation of a bird. Thus, flocks or associated groups of birds together were counted as 1 individual observation. For example, 2 counter-singing Tennessee Warblers would be recorded as 2 detections, but a flock of 15 Pine Siskins would be recorded as 1 detection. For our analysis of bird habitat associations, we examined the 20 most common species. We attempted to also run analyses on the Canada Warbler data, a blue-listed species, but model assumptions were violated due to a small sample size. We calculated density of each of the top 20 species within each polygon by dividing the total number of detections by the area of the polygon that fell within the 200 m radius of the point-count. For species richness, total abundance, and each of the top 20 species we summarized bird density (as a percentage) by habitat and age class. In addition to the top 20 species, we summarized habitat associations of woodpeckers detected during point counts. We used generalized-linear models (using a Poisson distribution with log-link function) to determine which habitat variables were important predictors of density for each of the top 20 species, as well as total density and species richness. This type of analysis is ideal for count data, which does not conform to assumptions of normality, is non-negative, and tends to be skewed towards zero. The total number of detections per polygon was entered as a dependant variable, and polygon area was entered as an offset variable, so that bird density was the variable being tested. Predictor variables were as follows: transect, stand classification, seral stage, and stand level (0 = road side, 1 = stand level) as factors, and percent canopy closure as covariates. Only main effects were considered, and all analyses were conducted in SPSS 15.0. Effects of habitat variables were considered significant if p > 0.05.
4. RESULTS
4.1 Survey Effort In our third year of roadside point count surveys, we surveyed a total of 592 points along 21 transects. We were able to survey all stations previously monitored in 2006 and 2007 (see MCA 2007 and MCA 2008). Eleven new stand-level points were set-up in 2008, bringing the total number of stand-level survey stations to 71.
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4.2 Abundance and Diversity
In total, we detected 5501 birds, of which 5311 were songbirds and woodpeckers. The average number of individual detections per point in 2008 was 8.0. This value was similar to the average per point detection rates in 2006 and 2007 (7.9 and 8.2 individuals per station, respectively). We detected 77 species of songbirds and woodpeckers in 2008, which is equal to the 2007 species richness. Both these years had higher species richness than 2006 (66 species), however; this was likely influenced by the increased sampling effort in later years.
The three most common species detected in all 3 years were Swainson’s Thrush Tennessee Warbler, and White-throated Sparrow, respectively (Table 2, see MCA 2007 and 2008 for previous years totals for all birds). Numbers of most species were similar between years, with some increase in detections from 2006 to 2007, and from 2007 to 2008. Species richness and number of birds detected per point varied with transect (Table 3). Species richness was highest on Kiwigana Road, Patry Road, and the 61 Road. Seven transects had greater than 40 species detected. Species richness was lowest on Stone Mountain and Muncho Lake transects. These were the only 2 transects to record less than 20 species, and they also had the lowest number of individual birds per point. The top transects for most birds per point were the 2400 Road, Luyben Road 1, Elleh Rd., and Kiwigana Road.
Table 2. Songbird species detected in the Fort Nelson Forest District in 2008, with total number of detections. Species for which a detailed habitat analysis was conducted are indicated in bold.
Common name Scientific Name Code Detections
Swainson’s Thrush Catharus ustulatus SWTH 508Tennessee Warbler Vermivora peregrina TEWA 504White-throated Sparrow Zonotrichia albicollis WTSP 377Ovenbird Seiurus aurocapilla OVEN 311Yellow-rumped Warbler Dendroica coronata YRWA 275Magnolia Warbler Dendroica magnolia MGNW 271Alder Flycatcher Empidonax alnorum ALFL 267Chipping Sparrow Spizella passerina CHSP 244Red-eyed Vireo Vireo olivaceus REVI 205Lincoln’s Sparrow Melospiza lincolnii LISP 182Ruby-crowned Kinglet Regulus calendula RCKI 166Dark-eyed Junco Junco hyemalis DEJU 145American Redstart Setophaga ruticilla AMRE 142
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Common name Scientific Name Code DetectionsWarbling Vireo Vireo gilvus WAVI 141Northern Waterthrush Seiurus noveboracensis NOWA 109American Robin Turdus migratorius AMRO 107Rose-breasted Grosbeak Pheucticus ludovicianus RBGR 103Least Flycatcher Empidonax minimus LEFL 95Western Tanager Piranga ludoviciana WETA 83Common Yellowthroat Geothlypis trichas COYE 82Hermit Thrush Catharus guttatus HETH 72Gray Jay Perisoreus canadensis GRJA 64Mourning Warbler Oporornis philadelphia MOWA 63Red-breasted Nuthatch Sitta canadensis RBNU 55Winter Wren Troglodytes troglodytes WIWR 44Fox Sparrow Passerella iliaca FOSP 43White-winged Crossbill Loxia leucoptera WWCR 43Swamp Sparrow Melospiza georgiana SWSP 42Canada Warbler1 Wilsonia canadensis CAWA 41Black-and-white Warbler Mniotilta varia BAWW 40Varied Thrush Ixoreus naevius VATH 31Hammond’s Flycatcher Empidonax hammondii HAFL 25Common Raven Corvus corax CORA 24Golden-crowned Kinglet Regulus satrapa GCKI 21Palm Warbler Dendroica palmarum PAWA 21Wilson’s Warbler Wilsonia pusilla WIWA 19Bay-breasted Warbler2 Dendroica castanea BBWA 18Black-capped Chickadee Poecile atricapillus BCCH 18Yellow-bellied Flycatcher Empidonax flaviventris YBFL 18Red-winged Blackbird Agelaius phoeniceus RWBL 16Orange-crowned Warbler Vermivora celata OCWA 14Yellow Warbler Dendroica petechia YEWA 14LeConte’s Sparrow Ammodramus leconteii LCSP 13Blue-headed Vireo Vireo solitarius BHVI 12Clay-colored Sparrow Spizella pallida CCSP 12Pine Siskin Carduelis pinus PISI 10Cape May Warbler2 Dendroica tigrina CMWA 9Brown Creeper Certhia americana BRCR 8Olive-sided Flycatcher3 Contopus cooperi OSFL 8Philadelphia Vireo Vireo philadelphicus PHVI 8Tree Swallow Tachycineta bicolor TRSW 7Boreal Chickadee Poecile hudsonicus BOCH 6Western Wood-Pewee Contopus sordidulus WWPE 6Cedar Waxwing Bombycilla cedrorum CEWA 5Townsend’s Warbler Dendroica townsendi TOWA 5Blackpoll Warbler Dendroica striata BKPW 3Cassin’s Vireo Vireo cassinii CAVI 3Common Grackle Quiscalus quiscula COGR 3
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Common name Scientific Name Code DetectionsEastern Kingbird Tyrannus tyrannus EAKI 3Red Crossbill Loxia curvirostra RECR 3Barn Swallow1 Hirundo rustica BASW 2Brown-headed Cowbird Molothrus ater BHCO 2Connecticut Warbler2 Oporornis agilis COWA 2Dusky Flycatcher Empidonax oberholseri DUFL 2Purple Finch Carpodacus purpureus PUFI 2Nelson’s Sharp-tailed Sparrow2 Ammodramus nelsoni NSTS 2Song Sparrow Melospiza melodia SOSP 2Cliff Swallow Petrochelidon pyrrhonota CLSW 1Eastern Phoebe Sayornis phoebe EAPH 1
Evening Grosbeak Coccothraustes vespertinus EVGR 1
Northern Rough-winged Swallow Stelgidopteryx serripennis NRWS 1
Savannah Sparrow Passerculus sandwichensis SAVS 1
1 Blue-listed in British Columbia 2 Red-listed in British Columbia 3 Threatened in Canada
Table 3. Songbird and woodpecker species richness, total numbers and average numbers detected per point (road side + stand level) for transects surveyed in the Fort Nelson Forest District, Spring 2008.
Transect Name Species Richness
Total Birds
Birds per Point
Number of Points
SYD Road 1 38 255 8.50 30 61 Road 44 239 7.97 30 Kyklo Road 34 235 7.83 30 SYD Road 2 36 230 7.67 30 Komie Road 1 33 211 7.03 30 Komie Road 2 25 136 4.53 30 Clarke Lake Road 43 289 8.50 30 + 4 Elleh road 43 339 9.69 30 + 5 Klua Road 36 246 8.20 30 Eskai Road 41 273 7.58 30 + 6 Kledo Road 30 207 9.41 22 Steamboat Road 40 302 8.88 24 + 10 Stone Mountain 15 99 3.30 30 Muncho Lake 15 76 2.53 30 Liard River Road 30 266 8.87 30 Pipeline Road 35 121 8.07 15 2400 Road 35 334 13.36 21 + 4 Luyben Road 1 41 400 11.76 30 + 4
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Luyben Road 2 31 209 5.50 30 + 8 Patry Road 45 390 9.07 30 + 13 Kiwigana Road 49 455 9.68 30 + 17 Total 78 5312 8.01 663
4.3 Habitat The transects we surveyed varied in forest age class and stand classification. Overall, most transects had high proportions of mid and late hardwood and softwood, and lower proportions of early seral stages of all stand types (Table 4, Figure 5). A high proportion of the total study area (on average, 30%) was not forested, and could be otherwise classified as meadow, wetland, recent cutblock, road, or road right-of-way. Transects with relatively high proportions of hardwood included Kyklo, Komie 2, Klua, and 2400 Road, whereas those with high proportions of softwood included SYD Road 2, 61 Road, Pipeline, and Luyben 2. Luyben Road 2, 61 Road, Clarke Lake., and 2400 Road each had relatively high proportions of late seral forest types, while the 2400 Road also had relatively high proportions of early seral forest types. Stone Mountain and Muncho Lake transects had no logging disturbance and high amounts of non-forested habitats.
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Table 4. Proportion of transects (expressed as a percentage of total area surveyed) categorized by stand classification and seral stage, Fort Nelson Forest District, Spring 2008.
Hardwood2 Softwood2 Mixedwood2 Transect Early1 Mid1 Late1 Total Early Mid Late Total Early Mid Late Total Cutblock Non-
Forested3
SYD Road 1 3.36 11.76 9.72 24.84 1.47 13.32 28.58 43.38 2.17 9.28 2.67 14.11 6.93 10.74 61 Road 0.00 11.11 0.00 11.11 0.00 28.00 43.91 71.91 0.00 7.51 2.58 10.09 0.15 6.74 Kyklo Road 0.00 69.46 5.65 75.11 0.00 1.86 1.17 3.04 0.00 2.81 0.00 2.81 0.00 19.04 SYD Road 2 0.65 17.02 0.40 18.07 0.00 44.01 16.79 60.81 0.21 4.03 0.33 4.56 0.28 16.29 Komie Road 1 0.00 33.12 0.00 33.12 0.00 38.63 6.89 45.52 0.00 8.68 0.00 8.68 0.00 12.68 Komie Road 2 0.00 56.68 0.00 56.68 0.00 20.17 7.52 27.69 0.00 2.94 0.00 2.94 2.54 10.14 Clarke Lake Road 0.00 7.56 13.93 21.49 0.17 12.77 38.72 51.66 3.57 1.49 5.51 10.58 7.27 9.00
Elleh road 0.00 25.07 8.88 33.96 0.00 15.67 2.48 18.15 0.00 1.13 0.08 1.21 32.24 14.44 Klua Road 1.44 44.54 8.90 54.89 0.39 10.21 12.73 23.33 0.00 0.00 0.89 0.90 8.51 12.37 Eskai Road 0.00 5.49 17.81 23.30 0.00 6.67 12.49 19.16 0.00 1.72 0.15 1.86 49.12 6.56 Kledo Road 0.48 4.99 12.12 17.59 0.00 13.90 15.92 29.82 0.00 0.59 5.65 6.23 38.62 7.74 Steamboat Road 0.00 5.58 17.24 22.82 0.00 0.00 37.95 37.95 0.00 1.43 19.83 21.26 13.89 4.08 Stone Mountain 0.00 0.00 1.04 1.04 0.00 11.30 34.84 46.13 0.00 0.00 0.00 0.00 0.00 52.82 Muncho Lake 0.00 0.00 0.00 0.00 0.00 33.94 13.83 47.77 0.00 7.41 0.00 7.41 0.00 44.82 Liard River Road 0.00 0.14 22.87 23.01 0.00 0.00 16.31 16.31 0.00 0.00 19.09 19.09 3.02 38.58
Pipeline Road 8.54 4.67 3.37 16.58 0.02 33.58 21.84 55.44 0.75 0.00 7.03 7.78 4.57 15.63 2400 Road 14.79 4.34 38.19 57.32 1.75 4.31 2.02 8.08 5.05 0.27 0.71 6.03 11.31 17.26 Luyben Road 1 6.02 0.00 31.56 37.58 0.06 3.22 27.84 31.13 0.16 0.89 0.24 1.29 18.82 11.18 Luyben Road 2 0.00 0.00 0.95 0.95 0.00 3.88 70.27 74.15 0.00 0.19 4.70 4.89 5.98 14.02 Patry Road 1.64 6.46 10.88 18.98 0.07 1.53 21.83 23.43 0.26 2.30 20.13 22.68 27.56 7.34 Kiwigana Road 1.10 0.26 36.79 38.15 0.00 0.47 9.25 9.73 0.00 1.25 17.28 18.53 26.13 7.46
1 Early ≤ 30 years, Mid = 31-89 years, Late ≥ 90 years. 2 Hardwood ≥ 70% Hardwood, Mixedwood = 31-69% Hardwood/Softwood, Softwood ≥ 70% Softwood 3 Not forested = rivers, lakes, swamps, recently harvested areas, non-commercial brush, roads and road right-of-ways
20
Stand Classification / Age Class
Tota
l Are
a (%
)
0
5
10
15
20
25
HWEarly
HWMid
HWLate
SWEarly
SWMid
SWLate
MWEarly
MWMid
MWLate
CB Non-Forested
1.51
14.20
12.14
0.17
12.86
21.63
0.522.56
5.65
15.58
13.18
Figure 5. Proportion of the study area as a function of stand classification (HW = Hardwood; SW = Softwood; MW = Mixedwood; CB = Cutblock) and age class in the Fort Nelson Forest District, Spring 2008.
4.4 Species at Risk Several species at risk were detected during point-counts. The Canada Warbler was detected in appreciable numbers (41 detections, Table 5), but other species at risk were detected rarely (Bay-breasted Warbler, Cape May Warbler, Connecticut Warbler, Cape May Warbler, Olive-sided Flycatcher, Philadelphia Vireo and Nelson’s Sharp-tailed Sparrow).
21
Table 5. Red-listed (threatened or endangered), blue-listed (special concern), or COSEWIC designated species detected during roadside and stand-level point counts, 2008.
Species No. of Detections Transects Recorded Status
Bay-breasted Warbler 18 1A, 1B, 4A, 4B, 5A, 10A, 10B Red
Barn Swallow 2 1B Blue
Canada Warbler 41 A1, 2A, 3B, 4A, 4B, 5A,
5B, 6A, 8A, 8B, 9A, 10A, 10B
Blue
Cape May Warbler 9 2A, 3A, 4A, 5B, 6A, 8B, 10A, 10B Red
Connecticut Warbler 2 4B, 10A Red LeConte’s Sparrow 14 1B, 2B, 8A, 10B Blue
Nelson’s Sharp-tailed Sparrow 2 9A, 10B Red
Olive-sided Flycatcher 8 4A, 4B, 6C, 7B, 10B Threatened*Sandhill Crane 4 1A, 1B Blue
*All status labels (blue and red) refer to B.C. Conservation Data Centre designations, except Olive-sided Flycatcher which is provincially yellow-listed, but is considered ‘threatened’ federally by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC).
4.5 Habitat Associations The passerine species commonly detected in our surveys varied in density depending on age class and stand classification (Table 6). No species had high proportions of detections in early seral stages (stands < 30 years of age) of hardwood, softwood, or mixed wood; however, Alder Flycatcher, and White-throated Sparrow were found in relatively high proportions in recent cutblocks. Eight species had relatively high proportions of detections in late seral stands (> 90 years) including Swainson’s Thrush, Magnolia Warbler, Warbling Vireo and Western Tanager. Although all species had low densities in non-forested areas, Dark-eyed Junco, Chipping Sparrow, and American Redstart had the highest densities in this habitat type. Overall species richness was positively correlated with early seral forest types. Species with relatively high detection densities with hardwood-dominated stands were the American Redstart, Least Flycatcher, Ovenbird, and Red-eyed Vireo (Table 7). The Yellow-rumped Warbler and Ruby-crowned Kinglet were detected mainly in mid- to late-seral softwood stands.
22
Table 6. Relative proportion of the 20 most abundant birds (expressed as a percentage) detected in different seral stages and stand classifications (including road-side and stand-level stations) in the Fort Nelson Forest District, spring 2008.
Hardwood Softwood Mixedwood Species Non
Forested Early Mid Late Total Early Mid Late Total Early Mid Late Total Cutblock
SWTH 5.6 3.7 15.6 18.7 38.0 0.4 8.3 21.0 29.7 0.4 2.9 9.1 12.4 14.3 TEWA 13.5 3.0 17.1 11.0 31.1 0.4 12.7 16.1 29.1 1.0 3.2 6.6 10.8 15.5 WTSP 8.0 1.7 10.5 12.4 24.6 0.8 7.7 9.7 18.2 1.1 0.6 3.6 5.2 43.9 OVEN 1.9 2.3 33.4 31.5 67.2 0.6 2.3 7.1 10.0 0.0 1.3 10.0 11.3 9.6 YRWA 13.8 0.4 10.0 6.7 17.1 0.0 18.6 34.6 53.2 0.0 3.0 9.3 12.3 3.7 MGNW 16.0 3.7 7.1 18.7 29.5 0.7 4.9 15.3 20.9 0.4 1.5 7.1 9.0 24.6 ALFL 16.0 3.0 7.2 5.7 16.0 0.4 12.9 11.0 24.3 1.5 2.7 0.4 4.6 39.2 CHSP 20.3 1.3 9.1 7.8 18.1 0.4 13.4 32.3 46.1 0.9 1.7 3.0 5.6 9.9 REVI 6.8 6.3 29.8 18.5 54.6 0.5 2.4 6.8 9.8 0.5 2.9 2.4 5.9 22.9 LISP 17.7 2.8 5.5 7.2 15.5 0.0 22.1 18.8 40.9 0.0 4.4 1.1 5.5 20.4 RCKI 10.5 0.0 5.6 6.8 12.3 0.0 20.4 46.3 66.7 0.0 1.9 4.9 6.8 3.7 DEJU 31.9 0.0 4.3 5.7 9.9 0.0 28.4 24.8 53.2 0.0 0.0 2.8 2.8 2.1 AMRE 18.3 9.9 23.2 20.4 53.5 0.0 2.1 5.6 7.7 2.1 0.0 3.5 5.6 14.8 WAVI 17.7 5.7 13.5 18.4 37.6 0.0 2.8 12.8 15.6 0.7 2.1 14.2 17.0 12.1 NOWA 6.4 1.8 22.0 9.2 33.0 0.0 23.9 14.7 38.5 0.0 5.5 5.5 11.0 11.0 AMRO 15.9 2.4 25.6 13.4 41.5 1.2 12.2 12.2 25.6 0.0 1.2 3.7 4.9 12.2 RBGR 4.0 8.9 12.9 20.8 42.6 1.0 4.0 7.9 12.9 1.0 1.0 7.9 9.9 30.7 LEFL 9.5 4.2 30.5 22.1 56.8 0.0 1.1 4.2 5.3 1.1 2.1 4.2 7.4 21.1 WETA 1.3 1.3 7.6 22.8 31.6 1.3 5.1 27.8 34.2 0.0 2.5 16.5 19.0 13.9 COYE 15.9 2.4 8.5 1.2 12.2 0.0 24.4 17.1 41.5 0.0 4.9 1.2 6.1 24.4
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Table 7. Relative proportion of the 20 most abundant birds (expressed as a percentage) detected in by seral stage in the Fort Nelson Forest District, Spring 2008. Values do not add to 100 since Non-forested and Cutblock areas were not included.
Species Early Seral Mid Seral Late Seral
SWTH 4.6 26.8 48.8 TEWA 4.4 32.9 33.7 WTSP 3.6 18.8 25.7 OVEN 2.9 37.0 48.6 YRWA 0.4 31.6 50.6 MGNW 4.9 13.4 41.0 ALFL 4.9 22.8 17.1 CHSP 2.6 24.1 43.1 REVI 7.3 35.1 27.8 LISP 2.8 32.0 27.1 RCKI 0.0 27.8 58.0 DEJU 0.0 32.6 33.3 AMRE 12.0 25.4 29.6 WAVI 6.4 18.4 45.4 NOWA 1.8 51.4 29.4 AMRO 3.7 39.0 29.3 RBGR 10.9 17.8 36.6 LEFL 5.3 33.7 30.5
WETA 2.5 15.2 67.1 COYE 2.4 37.8 19.5
Our generalized linear models highlighted species with strong habitat associations (Table 8). Swainson’s Thrush, Ovenbird, and Yellow-rumped Warbler showed preferences for interior forest; the latter two were also associated with closed canopies. Tennessee Warbler, White-throated Sparrow, Alder Flycatcher, Chipping Sparrow, and Lincoln Sparrow preferred roadside habitats. Habitat associations for this group of species included positive associations with hardwood and mixedwood (Tennessee Warbler), and a strong positive association with open areas such as cutblocks (White-throated Sparrow). Other strong positive associations included American Redstart and Warbling Vireo with hardwood and Warbling Vireo with mixedwood. We found strong negative associations for Ovenbird and Red-eyed Vireo with softwood. Responses towards stand age and canopy closure varied by species.
24
Table 8. Results from generalized linear models including stand classification, stand age, canopy closure, and transect as predictors of bird density (birds/ha) in the Fort Nelson Forest District, Spring 2008.
Species Transect Hardwood Softwood Mixedwood Cutblock Stand Level
Stand Age
Canopy Closure
SWTH * SL TEWA * + + RS - WTSP * ++ RS -- - OVEN * -- SL + YRWA * SL + MGNW * ALFL * RS - = - CHSP RS REVI * -- - + LISP * RS -
AMRE * ++ -- WAVI * ++ ++ NOWA * = - AMRO RBGR * - LEFL * - WETA + + COYE = -
Richness * -
* indicates that breeding density varied in function of transect. For the four categories of stand classification (including cutblock) a ‘-‘ indicates a negative association, ‘+’ a positive association. Single symbols indicate P < 0.05, a double symbol indicates a P < 0.01. ‘SL’ indicates a preference for Stand-level sites, ‘RS’ indicates a preference for Road side sites. For stand age, a ‘-‘ indicates association with early seral stands, ‘=’ indicates association with mid seral stands and ‘+’ indicates an association with late seral stage stands. For canopy closure, ‘-‘ indicates a preference for open canopy, ‘+’ indicates preference for closed canopy. The species that demonstrated positive associations with specific habitat types were White-throated Sparrow (cutblocks, Figure 6), American Redstart (hardwood, Figure 7), and Warbling Vireo (hardwood and mixedwood, Figure 8).
25
Forest Type / Age class
WTS
P de
nsity
(Bird
s / 1
00 H
ecta
res)
0
5
10
15
20
25
HWEarly
HWMid
HWLate
NonForested
SWEarly
SWMid
SWLate
MWEarly
MWMid
MWLate
CB
Figure 6. Density of White-throated Sparrow (WTSP) in relation to habitat types (HW = Hardwood; SW = Softwood; MW = Mixedwood; CB = cutblock) in the Fort Nelson Forest District, Spring 2008.
Forest Type / Age class
AM
RE
den
sity
(Bird
s / 1
00 H
ecta
res)
0
2
4
6
8
10
12
HWEarly
HWMid
HWLate
NonForested
SWEarly
SWMid
SWLate
MWEarly
MWMid
MWLate
CB
Figure 7. Density of American Redstart (AMRE) in relation to habitat types (HW = Hardwood; SW = Softwood; MW = Mixedwood; CB = cutblock) in the Fort Nelson Forest District, Spring 2008.
26
Forest Type / Age class
WAV
I den
sity
(Bird
s / 1
00 H
ecta
res)
0
1
2
3
4
5
6
7
HWEarly
HWMid
HWLate
NonForested
SWEarly
SWMid
SWLate
MWEarly
MWMid
MWLate
CB
Figure 8. Density of Warbling Vireo (WAVI) in relation to habitat types (HW = Hardwood; SW = Softwood; MW = Mixedwood; CB = cutblock) in the Fort Nelson Forest District, Spring 2008.
4.6 Woodpeckers Five species of woodpeckers were recorded during point-count surveys, most of which were detected at relatively low frequencies (Table 9). The Yellow-bellied Sapsucker was the most common woodpecker species detected in our study area with 71 detections, while the Black-backed Woodpecker was the rarest with 1. Woodpecker species detected were the similar to 2007. We detected 1 American Three-toed Woodpecker in 2007 but none in 2008, and no Black-backed Woodpecker in 2007 but 1 in 2008. All species with more than 10 detections were found predominantly in late seral habitats (Table 10), with varying distributions across different stand classification types. Northern Flicker, however, also had a high proportion of detections in non-forested habitat. Yellow-bellied Sapsuckers were predominantly found in hardwood stands, whereas detections of Pileated Woodpeckers were more evenly distributed between hardwood and softwood stands. Northern Flickers were found in greatest densities in late-softwood and non-forested habitats, differing from 2007 when they were more strongly associated with early-seral softwood habitats. Note that the association of flickers with non-forested or early seral stage forest likely reflects use of individual wildlife trees or other small, unmapped retention areas. Yellow-bellied Sapsuckers remain good indicators of late seral hardwood habitats (Table 10).
27
Table 9. Woodpecker species detected in the Fort Nelson Forest District, Spring 2008. Scientific names, four-letter code, and number of detections are shown.
Common Name Scientific Name Code Detections
Yellow-bellied Sapsucker Sphyrapicus varius YBSA 71Pileated Woodpecker Dryocopus pileatus PIWO 15Northern Flicker Colaptes auratus NOFL 12Hairy Woodpecker Picoides villosus HAWO 7Black-backed Woodpecker Picoides articus BBWO 1
Table 10. Relative proportion of woodpeckers (expressed as a percentage) detected in different seral stages and stand classifications in the Fort Nelson Forest District, Spring 2008.
Hardwood Softwood Mixedwood Species Non
Forested Early Mid Late Total Early Mid Late Total Early Mid Late Total Cutblock
YBSA 8.7 2.9 7.2 30.4 40.6 0.0 8.7 15.9 24.6 0.0 1.4 5.8 7.2 18.8 PIWO 0.0 0.0 0.0 30.8 30.8 0.0 15.4 30.8 46.2 0.0 7.7 7.7 15.4 7.7 NOFL 33.3 8.3 0.0 0.0 8.3 0.0 16.7 33.3 50.0 0.0 0.0 8.3 8.3 0.0
28
Stand Classification / Age Class
Woo
dpec
ker D
ensi
ty (B
ird /
100
Hec
tare
s)
0
1
2
3
YBSAPIWONOFL
NonForested
EarlyHW
MidHW
LateHW
EarlySW
MidSW
LateSW
EarlyMW
MidMW
LateMW
CB
Figure 9. Density of Yellow-bellied Sapsucker (YBSA), Pileated Woodpecker (PIWO), and Northern Flicker (NOFL) in relation to habitat types (HW = Hardwood; SW = Softwood; MW = Mixedwood; CB = cutblock) in the Fort Nelson Forest District, Spring 2008.
4.7 Stand Level Surveys A total of 494 birds of 46 species were detected at the 71 stand-level survey stations. No species were found exclusively at stand-level points in 2008. The Brown Creeper was strongly associated with interior stands as it was detected 7 times in stand-level surveys and only once at a roadside point. Swainson’s Thrush, Ovenbird, and Yellow-rumped Warbler were also associated with stand-level stations (Table 8). The Bay-breasted Warbler and Dusky Flycatcher had an equal number of detections at roadside and stand-level points.
29
5. DISCUSSION
5.1 Habitat Classification Although this project was focused on sampling forest songbirds, non-forested habitat was the second largest of our 10 habitat classes by area. This was influenced partially by the association of roads with industrial activity (and non-forest habitats such as road right-of-ways), and partially by the large areas of naturally occurring non-forested wetlands in the study area. Early seral habitats of all types were sampled less intensively than mid or late seral habitats. However, species associated with early seral habitats are often habitat generalists or respond positively to the effects of forest harvesting. Additionally, the spatial distribution and area of habitat classes will change over time as stands are harvested or are naturally disturbed and regenerate. Long-term monitoring will capture the changing representation of habitat classes across the landscape. Habitat classes were defined using provincial VRI data. The framework of this data is organized from a forest management, rather than an ecological perspective. For example, a seasonal wetland with a sparse tree cover of black spruce would be classified as non-forest by VRI data, yet still be utilized by forest songbirds. This may make it difficult to clearly identify species – habitat class associations. This approach is used in all Canfor Ltd monitoring projects in British Columbia (e.g., MCA 2007a, 2008a, 2008b, 2009). However, the use of VRI data is cost effective, and links songbird species with forest management metrics. This is critical if monitoring results are to be effectively incorporated into harvest planning.
5.2 Songbird Habitat Relationships Early seral habitats had both the highest richness and densities of forest songbirds. Many of these species are habitat generalists, and occurred in all seral stages. The early seral age class had the highest proportion of no detections for many species, though mid-seral mixedwood also had no detections of Dark-eyed Junco and American Redstart. This suggests that although early seral forests had the highest density or richness, mid and late seral stages contained species with more specific habitat requirements. Mixedwood had the fewest overall detections of the 20 most common bird species. Softwood and hardwood each had roughly the same number of detections, with softwood having slightly less than hardwood. However, the majority of significant species-specific habitat associations we found were with hardwood stands. For example, both American Redstart and Warbling Vireo both showed positive associations with young hardwood stands. This is consistent with Sherry and Holmes (1997) and Gardali and Ballard
30
(2000), who report associations with hardwood forest types with a well-developed shrub layer, usually indicative of younger seral stages. There is a paucity of research on the ecology of Ovenbird in British Columbia. Studies in eastern North America have found this species to be strongly associated with hardwood-dominated stands (Van Horn and Donovan 1994). We found similar trends in our study area, with the highest densities occurring in mid- and late-seral hardwood stands. Increased canopy closure and tree height are consistently identified as important for this species (Van Horn and Donovan 1994). In our study area, Ovenbirds were positively associated with canopy closure. Overall, our data suggests that mid-seral or older, closed-canopy, hardwood dominated stands are preferred Ovenbird habitat in the FNFD. The results in 2008 were consistent with 2007, suggesting that mid- to late-seral hardwoods are an important habitat type for Ovenbird in the Fort Nelson Forest District. At the time of this analysis, data did not exist to enable us to examine the relationship between bird density and habitat elements such as snags or coarse woody debris. Species that showed no associations with the broad habitat classes in our analysis may be responding to the availability of a specific habitat element. For example, Winter Wrens are associated with coarse woody debris and well-developed shrub layers within a broad range of forest types (Hejl et al. 2002). Bunnell (2005), however, notes that because of the generally less complex range of forest structures in northeastern British Columbia, broad habitat classes may act as an adequate surrogate for structural elements.
5.3 Woodpecker – Habitat Relationships Woodpeckers are an ecologically important taxonomic group because they: a) provide important ecological services such as creating nest cavities for secondary-nesting species (Fenger et al. 2006); and b) rely on dead or dying wood, thus making them particularly susceptible to logging and post-fire salvaging activities (Virkkala 2006). We were not able to conduct an in-depth analysis of woodpecker habitat associations due to small sample size. However, from observed trends in woodpecker density across different habitat types we were able to infer certain habitat associations. The Northern Flicker was the least dependent species on mature forest stands, and was found at equally high densities in both non-forested and late softwood stands in 2008, versus an early softwood association in 2007. This species prefers open habitats, and will use clearcuts and fragmented habitats as long as there are snags in the vicinity (Moore 1995). Yellow-bellied Sapsuckers were associated primarily with mature hardwood stands in our study, consistent with findings by Savignac and Machtans (2006) that this species requires mature hardwood stands for nesting and foraging, and that stand rotations of >90 years are probably necessary to maintain viable populations. Habitat requirements of Yellow-belied Sapsuckers were similar in 2007 and 2008. The Hairy Woodpecker had few detections in 2008, and the Black-backed Woodpecker was only detected once. Pileated Woodpeckers were strongly associated with late seral forest types, with equal detections between hardwood and softwood habitats, but few in
31
mixedwood stands. The association with late seral stands is well documented for this species, as is its use of both deciduous- and coniferous-leading stands (e.g., Bull and Jackson 1995).
5.4 Songbirds in Interior Forest Stands Overall, fewer birds were detected per point in interior forest habitats compared with roadside habitats. This may be a reflection of the higher overall bird densities in early seral habitat, while all our stand-level point count stations were located in late-seral stands. When we analysed only late-seral stands, there was no significant difference between total bird densities or richness in roadside versus stand-level habitats. This pattern varies temporally by species. For example, we detected Bay-breasted Warbler only in interior forest stands in 2007 (n = 7), but evenly in both interior and roadside stands in 2008 (n = 18). Bay-breasted Warblers breed in mature coniferous forests and avoid open or fragmented habitats such as roads or clearcuts (Williams 1996, Cooper et al. 1997b, Droler et al. 1999, Potvin and Bertrand 2004). However, populations of this species are strongly associated with the presence of spruce budworm (Choristoneura fumiferana), and may be present over greater areas in years when these caterpillars are plentiful (see Williams 1996). Species with strong positive associations to interior forest habitats tended to be those generally associated with mature forests, whereas those found predominantly in roadside habitats were species primarily associated with early-seral stage habitats. Ovenbirds were strongly negatively associated with roadside habitats, indicating a preference for un-fragmented forests in our study area. This association with interior forest, as well as the preference for high canopy cover, has been reported elsewhere in the Ovenbird’s range (Van Horne and Donovan 1994). Yellow-rumped Warblers were frequently detected and found in all forest types and seral stages; their association with interior forest in this study is probably an artefact of its generalist use of habitat (Hunt and Flaspohler 1998). Similarly, American Redstarts were not positively associated with interior forest habitats in 2008 as opposed to 2007. American Redstarts are also associated with a broad spectrum of seral stages and age classes (Sherry and Holmes 1997). Five species (Tennessee Warbler, White-throated Sparrow, Alder Flycatcher, Chipping Sparrow and Lincoln’s Sparrow) had significant positive associations with roadside habitats. All of these species are common in early successional habitats and may benefit from forest fragmentation (Falls and Kopachena 1994, Ammon 1995, Middleton 1998, Rimmer and Mcfarland 1998, Lowther 1999). Our comparisons of bird densities in stand-level and roadside points highlighted the fact that roadside surveys may provide slightly biased density estimates in comparison to un-fragmented landscapes, depending on the species. Stand-level surveys allowed us to identify species that may be poorly represented in roadside surveys. Furthermore, we were able to identify species (such as the Ovenbird) that may be susceptible to edge
32
effects, and should be monitored for long-term changes in abundance in managed landscapes.
5.5 Species at Risk Several red and blue-listed species were detected in the study area, and may warrant special consideration due to concerns about their populations in British Columbia. Most of these species, such as the Canada Warbler, are at the extreme western portion of their range and are sparsely distributed in the province (Cooper et al. 1997; Campbell et al. 2001). Species such as Bay-breasted Warbler are becoming increasingly rare throughout their range, due in large part to human activities such as insect spraying and harvesting of mature forests (Williams 1996, Conway 1999). Within the FNFD, several areas surveyed in this study had concentrations of species at risk detections. Forests along the Kiwigana Road, for example, had the greatest diversity of species at risk in both 2007 and 2008. The Patry Road transect had the most detections of species at risk in 2008, but is in the same general area of the forest district as the Kiwigana Road. The Kiwigana Road and Patry Road transects had some of the highest proportions of late-seral hardwood and mixedwood, respectively, further suggesting the importance of these habitats to rare songbird species.
5.6 Implications for Forest Management Mature hardwood stands are currently a focus of commercial harvest activities in the FNFD. Based on our results indicating that mid- to late-seral hardwood stands are important to a suite of bird species; management planning and implementation of forest practices which retain habitat structure in these stands may be necessary. Existing targets for retention of mid- and late-seral hardwood forest types should be examined in this context. The Ovenbird may be useful as a candidate focal species to assess the effectiveness of forest management practices in maintaining sufficient intact patches (i.e., size and distribution across the landscape) of mid- and late-seral hardwood. The mid- and late-seral hardwood stands favoured by the Ovenbird in the FNFD are also important for other species at risk in British Columbia including Canada Warbler (Enns and Siddle 1996, Cooper at al. 1997, MCA 2007b), Connecticut Warbler (Cooper et al. 1997c, Pitochelli et al. 1997), and Philadelphia Vireo (which is currently yellow-listed in BRITISH COLUMBIA, see Moskoff 1996, Cooper at al. 1997d). In the forests of northwestern Alberta, Ovenbird populations responded negatively to partial cutting (Harrison et al. 2005). In the boreal forest of Ontario, Rempel (2007) identified Ovenbird as one of a set of focal species in an effectiveness monitoring program. By monitoring long-term population trends of Ovenbird, inferences can be made about both the amount of hardwood habitat and its distribution on the landscape. While some researchers have cast doubt on the validity of point-counts to provide indices of abundance (e.g., Anderson 2001, Buckland 2006, Kissling and Garton 2006), recent
33
evidence re-affirms the strength of point-count survey data in extensive, multiple-species surveys (Johnson 2008). Recent work suggests that using point-count data for population-level assessments is appropriate and complements other population-level surveys such as the Monitoring Avian Productivity and Survivorship (MAPS) program (Saracco et al. 2008). Results presented in this report will be an important component of Canfor Ltd.’s overall sustainable forest management planning initiative in the FNFD.
34
6. REFERENCES Ammon, E.M. 1995. Lincoln's Sparrow (Melospiza lincolnii), The Birds of North
America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology. http://bna.birds.cornell.edu/bna/species/191.\ [Accessed 25 January 2009]
Anderson, D.R. 2001. The need to get the basics right in wildlife field studies. Wildlife
Society Bulletin 29: 1294-1297. Böhning-Gaese, K., M.L. Taper, and J.H. Brown. 1993. Are declines in North American
insectivorous songbirds due to causes on the breeding range? Conservation Biology 7: 76–86.
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Appendix 1. Example of orthophoto with point count detections in the Fort Nelson Forest District, 2008.
41
Appendix 2. Non-target species (i.e., species other than songbirds and woodpeckers) detected in the Fort Nelson Forest District, Spring 2008. Scientific names, four-letter code, and number of detections are shown.
Common Name Scientific Name Code Detections
Wilson’s Snipe Gallinago delicata WISN 52 Solitary Sandpiper Tringa solitaria SOSA 26 Sora Porzana carolina SORA 24 Spotted Sandpiper Actitis macularia SPSA 11 Bufflehead Bucephala albeola BUFF 9 American Kestrel Falco sparverius AMKE 8 Greater Yellowlegs Tringa melanoleuca GRYE 8 Ruffed Grouse Bonasa umbellus RUGR 8 Lesser Yellowlegs Tringa flavipes LEYE 7 Green-winged Teal Anas carolinensis GWTE 4 Sandhill Crane Grus canadensis SACR 4 American Wigeon Anas americanas AMWI 3 Blue-winged Teal Anas discors BWTE 3 Belted Kingfisher Megaceryle alcyon BEKI 2 Canada Goose Branta canadensis CAGO 2 Lesser Scaup Aythya affinis LESC 2 Northern Shoveler Anas clypeata NOSH 2 Ring-necked Duck Aythya collaris RNDU 2 Red-tailed Hawk Buteo jamaicensis RTHA 2 Barrow’s Goldeneye Bucephala islandica BAGO 1 Gadwall Anas strepera GADW 1 Herring Gull Larus argentatus HEGU 1 Horned Grebe Podiceps auritus HOGR 1 Killdeer Charadrius vociferous KILL 1 Merlin Falco columbarius MERL 1 Northern Hawk Owl Surnia ulula NHOW 1 Pied-billed Grebe Podilymbus podiceps PBGR 1 Sharp-shinned Hawk Accipiter striatus SSHA 1 Trumpeter Swan Cygnus buccinator TRUS 1
