Browsing by Author "Hanowski, JoAnn M"

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Avian Assessment Document: Avian Population Analysis for Wind Power Generation Regions--012
(University of Minnesota Duluth, 1997) Hawrot, Rita Y; Hanowski, JoAnn M
Our objective was to gather avian information for potential wind power development areas in western Minnesota to assist in the siting of wind energy facilities in Minnesota. We compiled an annotated bibliography of national and international.sources to identify factors that may affect avian activity relative to wind power development. We gathered information on avian population data in this region from 10 sources for 43 counties within the three wind tiers. One federally threatened species, the Bald Eagle (Haliaeetus leucocephalus) is known to nest in this region. Because breeding bird activity for most species is completed at low elevations it is not likely that they would be directly affected by wind towers. Background information gathered indicated that migratory birds were likely to be most at risk from potential wind power development in the western portion of Minnesota. Information gathered on migratory bird activity on 18 sites in three wind regions over four seasons indicated that migratory activity was quite variable, was inconsistent across sites, and only a few differences were detected in number of migrants across the three regions. We observed fewer targets in the area (near Marshall) with the highest potential for wind development in spring 1996. This pattern was not found in the other seasons of observation (fall 1995 and 1996 and spring 1997) and this inconsistency makes it difficult or impossible to rank areas for potential wind development that integrates concerns for migrating birds. Migratory bird activity in this region is quite variable and landscape features that birds respond to are not static. For example, daily movements of birds during staging are affected by local cropping patterns during both spring and fall periods and amount of winter snowfall affects distribution of water across the landscape during spring migration. We can be safe to recommend that tower construction in areas that bisect daily movement be avoided because these flights are generally done at lower altitudes than long-range migration and at an elevation that would be consistent with tower height. There is an inherent risk associated with construction of any tall structure and we can never be 100% certain that bird collisions can be avoided at any site. In general, it is impossible to calculate the simultaneous occurrence of birds migrating over a wind tower facility during bad weather. The annual incidence rate, however, would likely be lower than the number killed by vehicles or house cats.
Bird Population Trends in Minnesota and Northwestern Wisconsin Forests, 1991-1997
(University of Minnesota Duluth, 1998) Hawrot, Rita Y; Hanowski, JoAnn M; Lima, Ann R; Niemi, Gerald J; Pfannmuller, Lee
The status of forest birds has been the subject of considerable interest (Terborgh 1989). Longterm monitoring can be used to identify species at risk by providing information on abundance patterns. We previously summarized our results on bird population trends in the Chippewa and Superior National Forests (NF), Minnesota, after three years of monitoring (Hanowski and Niemi 1994). In both forests, the Gray Jay, Winter Wren, Nashville Warbler, and American Redstart increased significantly and the White-throated Sparrow and Red-eyed Vireo decreased significantly. We also looked at population trends of breeding birds in Minnesota and Minnesota forested regions over the past 28 years using data from the North American Breeding Bird Survey (BBS), a continental monitoring program which uses roadside counts to sample breeding birds (Sauer et al. 1997) (Niemi et al. 1995). Forty-two percent of species (49 species) examined had no significant change in abundance,'36% (42 species) had significant increases, and 21% (25 species) had significant declines. Most species with declining trends could be grouped into three broad categories: species associated with forests, species of agricultural landscapes, and species associated with wetlands. In 1997, we completed the seventh year of our forest breeding bird monitoring program. Since the program’s initiation in 1991, we have added three study areas: the Chequamegon NF of northwestern and central Wisconsin, and Minnesota’s St. Croix River Valley (St. Croix) in 1992; and southeastern Minnesota (Southeast) in 1995 (Figure 1). Northern Minnesota and northwestern Wisconsin are located in the southern boreal-northern hardwood forest border (Pastor and Mladenoff 1991). Much of the conifer forest has been converted to aspen and birch since the middle of the last century (Coffin and Pfannmuller 1988). The present landscape has fewer conifer stands and more deciduous stands such as aspen and birch (Green 1995). Southeast Minnesota and central Wisconsin (southern most extent of the Chequamegon NF) are part of the eastern deciduous forest. Forests in this region have been altered by agricultural development or urban growth (Coffin and Pfannmuller 1988). We are currently monitoring five study areas by conducting over 1600 habitat-specific point counts each breeding season (Howe et al. 1997). Our objectives are to (1) identify species that have significant population trends for each study area; (2) identify species with significant population trends over the region; and (3) compare our results to trends from Minnesota BBS.
Bird Usage of Hybrid Poplar Plantations Annual Progress Report 1996
(University of Minnesota Duluth, 1997) Hanowski, JoAnn M; Niemi, Gerald J
We continued to collect baseline data on the large plantations that have been established in the Alexandria area. Three sites have been surveyed for four years, six sites for three years, and four sites f.or two years. We observed a linear growth in mean numbers of individuals and species on plantations as they have aged from one to six years. Species diversity has plateaued after five years on two sites. Plantations that had partial tree failure in previous years had greater species diversity. This was expected because these sites have two or three ages of trees present on the site and were more heterogeneous in the bird habitat they provided. Species turnover rates were 57% for plantations that aged from one to two years and were 53% for plantations that aged from two to three years. The largest proportion of bird individuals in plantations in the first six years were short-distance migrants. Numbers of individuals that migrate long-distances to Central and South America increased slightly as the plantations aged. Very few permanent resident birds were found in plantations at any age. Most individuals observed in the plantations at all ages were ground feeding birds associated with open field and pasture habitats. Very few foliage gleaners individuals and those associated with forested habitats were observed in the plantations at any age. Numbers of shrub birds and those that eat seeds increased as the plantations have grown. Studies were again (repeated from 1995) conducted on predation rates of artificial bird nest~ to test the hypothesis that predation rates in forests and grasslands adjacent to plantations are not affected by distance to the edge of the plantation. Data collected on predation rates this past summer support the alternative hypothesis that predation rates are independent of habitat type and distance from edge of plantation. We found that predations rates were site specific and were likely affected by local predator populations. These results support conclusions made from similar studies collected in 1995. The geographic information system (GIS) that included land cover types within a 2-3 mile radius of each plantation in the Alexandria area (for details see small mammal report) was completed. Canonical correspondence analyses (CANOCO) on the plantations established after or during 1994 indicated that the landscape surrounding many plantations was similar and was dominated by cropland. Exceptions to this were the Kreyer and Nelson sites which had .more water, woodland, and pasture (Kreyer) and wet and dry wildland (Nelson) in the surrounding landscape. Bird species such as the Sedge Wren, Mallard, Common Yellowthroat, Ring-necked Pheasant, Blue-winged Teal found within the Nelson site relected the presence of the adjacent wet and dry wildland habitat. The Chipping Sparrow, Eastern Bluebird, Grasshopper Sparrow and Vesper Sparrow found in the Kreyer site reflected the composition of the surrounding forest and pasture habitat.
Bird Usage of Hybrid Poplar Plantations Annual Progress Report 1997
(University of Minnesota Duluth, 1998) Hanowski, JoAnn M; Niemi, Gerald J
'We continued to collect baseline data on the large plantations that have been established in the Alexandria area. Three sites have been surveyed for four years, six sites for three years, and four sites for two years. We continued to see a general pattern of an increase in species diversity and overall abundance as plantations have aged from one to five years. Older plantations (six and seven years) had fewer individuals than age five plantations, but this could be attributed to the fewer number of plantations that we have surveyed in the older age categories. Individual species observed on plantations indicated that open country birds continued to dominate the younger plantation community and early-successional species were most common on the three to five year old sites. Forest edge species were present on two older plantations but were also recorded on several four year old plantations. Very few forest species were observed in plantations of any age. Species turnover rates for individual sites indicated that community composition is unstable. Turnover was generally lower on sites after they have reached age five and higher on sites up to age four. The relatively high rate for the Belle River site from 1996 to 1997 is difficult to interpret, but could indicate that the community is changing from an early- successional species composition to a community that has more forest birds. Additional data are needed to confirm this observation. The highest proportion of individuals observed in the plantations of all ages were seed and insect eaters that feed on the ground. Based on the habitat guild summaries, it is evident that birds that prefer open fields and meadows dominated the bird community from ages 1 to 4. Bird species that prefer wet shrub, open wetland, or aquatic habitats were present in small numbers in plantations of all ages. The presence of these bird species on plantations were likely due to the influence of surrounding landuse types or by small wetland inclusions within the plantations. At age five and six a few species that occupy deciduous forests began to colonize the plantations. The largest proportion of bird species that occurred on plantations in the first six years were short-distance migrants. Very few resident birds were found in plantations at any age. Data collected on predation rates this past summer indicate that predation rates are independent of habitat type (including the plantation). For example, predation rates in plantations averaged 20% and the adjacent CRP rate was 10%. In addition, average rate for forests adjacent to plantations was 25% compared to 20% in the plantations. We have developed a geographic information system (GIS) that includes land cover types within a 2-3 mile radius of each plantation in the Alexandria area. Information gathered on birds over the past six years will be used as inputs for a geographical model to predict bird responses to plantation development. Initial values for bird species to be implemented into the model were calculated. Landuse change simulation models will be run to predict bird changes in response to plantation development and growth in this region.
Bird Usage of Hybrid Poplar Plantations Five Year Report 1992-1996
(University of Minnesota Duluth, 1997) Hanowski, JoAnn M; Niemi, Gerald J
Our efforts over the past five years have focused on one overall objective; to understand the habitat value of hybrid poplar plantations to breeding and migrating birds. Several objectives, with testable hypotheses were developed to address this overall objective. These hypotheses revolve around three central themes. The first is to determine how habitat changes with 1) plantation age, 2) size of plantation, 3) within plantation habitat, and 4) landscape context. The second set of hypotheses address the impacts of converting existing land to hybrid poplar considering; 1) type of habitat replaced, 2) landscape composition surrounding plantation, 3) within plantation plantings to enhance wildlife habitat value, and 4) affects of plantation on surrounding bird communities including assessment of predation events. Thirdly, we are focusing our efforts towards modeling these data spatially. Information required for these models include; 1) size of plantation, 2) landscape composition, 3) growth rates of trees, and 4) bird species composition at different stages of plantation succession.
Breeding Bird Communities Across an Upland Disturbance Gradient in the Western Lake Superior Region
(2007) Miller, Christina; Niemi, Gerald J; Hanowski, JoAnn M; Regal, Ronald R
The coastal region of western Lake Superior to examine relationships to human land use. Eighty-four species were detected and 50 were abundant enough to be included in data analysis. Monotonic quadratic regression models were constructed for these 50 species by using species counts as the dependent variable and the proportion of human conversion of the landscape (residential, agriculture, and commercial/industrial land uses) within each study area as the independent variable. Twenty-seven bird species had significant regressions (P < 0.05), 18 of which generally avoided areas developed by humans and 9 of which were attracted to development. De-trended correspondence analysis using counts of these 27 bird species was used to investigate multivariate, community responses to development. The first DCA axis was interpreted as a gradient from urban avoiding to urban exploiting bird species and was strongly correlated with land cover variables related to human development. Our results advance the idea that breeding bird communities can be used as indicators of ecological condition and can diagnose potential causes for changes in these conditions. Further, our study points out the usefulness of bird monitoring data in regional planning efforts that incorporate goals for maintaining native biological diversity.
Breeding Bird Monitoring in Great Lakes National Forests : 1991-2003
(University of Minnesota Duluth, 2003) Lind, Jim; Danz, Nicholas P; Hanowski, JoAnn M; Niemi, Gerald J
A total of 132, 134, and 169 stands (1,271 survey points) were surveyed for breeding birds in the Chequamegon, Chippewa, and Superior National Forests, respectively in 2003. Annual surveys have been conducted since 1991 in the Chippewa and Superior National Forests, and since 1992 in the Chequamegon National Forest. Breeding bird surveys in the St. Croix region of Minnesota have been conducted since 1992 on 170 stands (170 points). • We examined trends in relative abundance for 68 bird species in at least one of the four study areas. Fifty-five species in the Chequamegon NF, 52 in the Chippewa NF, 44 in the Superior NF, and 41 in the St. Croix region were tested for population trends. Thirty-six species were also tested for regional trends by combining data from the three national forests. • A total of 192 species/study area trends were calculated (not including regional trends), 98 (51%) of which were significant (P < 0.05). Twenty-five species increased significantly (P < 0.05) in at least one study area and 31 species decreased. • Seven species had significant increasing regional trends and 14 had decreasing trends. Six species had highly significant (P < 0.01) increasing trends in multiple study areas, and nine species had highly significant decreasing trends in multiple study areas. • The percentage of increasing species in each study area ranged from 13% in the Chequamegon NF, to 29% in the St. Croix study area. The percentage of decreasing species ranged from 25% in the Chequamegon NF study area, to 35% in the Chippewa NF. • There were 12 instances where a species wasn’t increasing in a particular study area in 2002 results but is increasing in 2003, and ten instances where a species showed a significant increase in 2002, and isn?t in 2003. Conversely, there were 19 instances where a species wasn’t decreasing in 2002 but is decreasing in 2003, and one instance where a species showed a decrease in 2002 but isn’t in 2003. • Short-distance migrants showed highly significant declines in all study areas. Long-distance migrants showed mixed results, including declines in the Chequamegon and Superior NF’s，an increase in the St. Croix study area，and a stable trend in the Chippewa NF. Permanent residents increased on all study areas except the Chequamegon NF, where they were stable. • Ground nesting birds showed highly significant declines in all study areas, with shrub and sub-canopy nesters increasing in all study areas. Canopy and cavity nesters showed mostly stable trends. Of the five vegetation-type preference guilds tested, lowland coniferous forest birds, deciduous, and mixed forest bird species showed widespread declines on our study areas, and upland coniferous species increased on all study areas except the Chequamegon NF. The early-successional guild showed an increase in the Chippewa NF and declines in the Superior NF and the regional analysis. • Evidence from recent regional studies have demonstrated greater nest predation rates on ground nests near forest/clearcut edges, as well as a significant increase in the creation of forest edges in recent years. Landscape fragmentation and nest predation may be having negative effects on declining ground-nesters such as the Winter Wren, Hermit Thrush, Black-and-white Warbler, Ovenbird, and White- throated Sparrow. • Of the 1445 survey sites in all four study areas, 13.4% have been at least partially harvested since the beginning of monitoring, which is about 1% a year. This harvest rate is comparable to the 4.8% change from mature forest to early- successional types on federally managed forest lands in northeastern Minnesota between 1990 and 1995 (i.e. -1% annual change). • Many of the declining trends that we have detected have been consistent across the years and are not likely due to annual variation. One of the main goals of this monitoring program is to identify species of conservation concern, and species such as the Eastern Wood-Pewee, Winter Wren, Hermit Thrush, Mourning Warbler, Ovenbird, and White-throated Sparrow probably need special management consideration by agencies such as the U.S. Forest Service and state Department of Natural Resources. Although most of these are common species, several are currently well below their estimated RNV values and they may not remain common if their declining trends continue.
Breeding bird monitoring in Great Lakes National Forests: 1991-1998
(University of Minnesota Duluth, 1999) Hanowski, JoAnn M; Niemi, Gerald J; Hawrot, Rita Y; Lima, Ann R
A total of 133, 162, and 128 stands (1,269 census points) were surveyed in the Chippewa, Superior and Chequamegon National Forests, respectively. Surveys have been completed for 8 years in the Chippewa and Superior and for 7 years in the Chequamegon. One-hundred seventy census points were surveyed in East Central Minnesota over the past 7 years and 211 census points in Southeast Minnesota over the past 4 years. A total of 74 species were abundant enough in at least one region to test for trends in annual abundance. Fifty species in the Chippewa National Forest, 45 species in the Superior National Forest, 50 species in the Chequamegon National Forest, 32 species in East Central Minnesota, and 38 species in Southeast Minnesota were tested. The average number of species and individuals observed/stand or point in four of five study regions were at an all time high in 1998. In contrast, the lowest number of species and the second lowest numbers of individuals were observed in Southeast Minnesota in 1998 than in the previous three years. A In the Southeast Minnesota region 57% of the species tested showed a significant trend in abundance. In the other four regions, 84 to 98% of the species tested exhibited a significant trend in abundance. Almost 30% of the species in Southeast Minnesota showed significant linear decreasing trends from 1995 through 1998 and an additional 19% had negative overall trends. Ten percent of the species in Southeast Minnesota had increasing abundance trends. In contrast, in the other four regions more than 63% (63 to 74%) of the species have increased in abundance from 1991 (or 1992) to 1998. The percent of the species that have declined in the other regions ranged from 25% in the Superior National Forest to 12% in the Chippewa National Forest. A total of 38 species showed significant decreases (linear or other) in at least one region. Of these, 22 species (59%) also increased significantly in another region. Fifteen species decreased in one or more regions without indicating increases in other regions. Ten species declined in one region and six species, the Downy Woodpecker, Golden-crowned Kinglet, Gray Catbird, Canada Warbler, Indigo Bunting and American Goldfinch declined in two regions. About 64% (7 of 11) of the permanent residents tested showed a significant decrease in one region. The proportion of short distant migrants that declined was about 40% (9 of 22) of the total number tested and about 55% (22 of 40) of the long distant migrants tested decreased in abundance in one region. When species were categorized by nest location, the largest proportion of species decreasing were cavity and canopy nesting species. The proportion (all about 50%) of species declining within general habitat groups was almost equal across open, young forest, and forest habitat groups. The spring of 1998 was affected by the El Nino weather pattern and was warmer than average in all regions. Precipitation was lower in April than normal, but wetter than normal in the other spring months. June in all regions was cooler and wetter than normal. The warm spring in the Great Lake’s area affected: 1) timing of permanent resident breeding which was earlier than normal, and 2) timing of short distance migrant arrival which was also earlier than normal. Arrival times of long distance migrants were not affected by local weather patterns. We speculate that breeding of long distance migrants was also somewhat earlier in 1998. This is supported by the observations of more than the average number of fledglings during our late-June and early July survey dates. It is also likely that more double brooding occurred in 1998 due to the favorable weather conditions, although we have no data to support this hypothesis. Another potential reason for an increase in numbers of individuals in 1998 is also related to the warm spring weather and the theory of heterospecific attraction. Our data support this hypothesis: number of breeding migrants over the eight years of monitoring was highly correlated (r=0.701 and p< 0.001) with the number of foliage and bark gleaning insectivorous permanent residents. Specifically, in years where we observed the greatest numbers of Black-capped Chickadees, Red- and White-breasted Nuthatches and Blue Jays we also recorded the largest number of migrant individuals. Four of the six species that decreased in abundance in more than one region (Gray Catbird, Canada Warbler, Indigo Bunting and American Goldfinch) are associated with early successional, edge, or shrub habitat. Of the other two species that declined, the Downy Woodpecker occurs predominantly in mature deciduous forests and the Golden-crowned Kinglet is most abundant in mature lowland conifer habitat. It is difficult to determine the exact cause of these species declines. However, more detailed studies may be required for these species if declines continue.
Breeding bird monitoring in Great Lakes National Forests: 1991-1999
(University of Minnesota Duluth, 2000) Lind, Jim; Danz, Nicholas P; Jones, Malcolm T; Hanowski, JoAnn M; Niemi, Gerald J
A total of 135, 168, and 133 stands (1,268 survey points) were surveyed for breeding birds in the Chippewa, Superior, and Chequamegon National Forests, respectively. Surveys have been completed for nine years in the Chippewa and Superior, and for eight years in the Chequamegon NF. Breeding bird surveys in the St. Croix region of Minnesota have been conducted over the last eight years at 171 points. Surveys in Southeast Minnesota have been conducted over the last five years at 211 points. We were able to examine trends in abundance for 79 bird species in at least one of the five study areas. Fifty-two species in the Chequamegon NF, 48 species in the Superior NF, 53 species in the Chippewa NF, 33 species in the St. Croix region, and 35 species in Southeast Minnesota were tested. Sixteen species showed a significant increase in at least one of the five study areas, and 13 species showed a significant decrease. Of the 16 increasing species, the American Robin, Yellow-rumped Warbler, and American Redstart showed significant increases in more than one study area. Of the 13 decreasing species, six declined significantly in more than one study area. The Eastern Wood-Pewee, Black-and-white Warbler, Ovenbird, Mourning Warbler, and Brown-headed Cowbird declined in two study areas and the White-throated Sparrow declined in three study areas.
Breeding bird monitoring in Great Lakes National Forests: 1991-2000
(University of Minnesota Duluth, 2001) Lind, Jim; Danz, Nicholas P; Jones, Malcolm T; Hanowski, JoAnn M; Niemi, Gerald J
• A total of 135, 168, and 133 stands (1,268 survey points) were surveyed for breeding birds in the Chippewa, Superior, and Chequamegon National Forests, respectively. Surveys have been completed for ten years in the Chippewa and Superior, and for nine years in the Chequamegon NF.• Breeding bird surveys in the St. Croix region of Minnesota have been conducted over the last nine years at 171 points. Surveys in southeast Minnesota have been conducted over the last six years at 211 points.• We were able to examine trends in abundance for 72 bird species in at least one of the five study areas. Fifty species in the Chequamegon NF, 40 species in the Superior NF, 47 species in the Chippewa NF, 36 species in the St. Croix region, and 36 species in Southeast Minnesota were tested.• Twenty-nine species showed a significant increase (P < 0.05) in at least one of the five study areas, and 23 species showed a significant decrease. The Least Flycatcher showed significant increases (P < 0.01) in two study areas and the American Robin increased in three study areas. The Eastern Wood-Pewee, Black-and-white Warbler, and Brown-headed Cowbird showed significant declines (P < 0.01) n two study areas and the Common Yellowthroat and White-throated Sparrow declined in three study areas.• Nine (18%) of the species tested in the Chequamegon NF had increasing trends and nine (18%) had decreasing trends. In the Chippewa NF, 12 (26%) of the species tested increased significantly and 10 (21%) decreased. Seven (18%) of the species tested in the Superior NF had significant increasing trends, and seven (18%) had decreasing trends. In the St. Croix study area, six (17%) of the species tested increased significantly, and seven (19%) decreased. In the Southeast, ten (28%) species increased significantly and three (8%) decreased.• The regional analysis of the three National Forests combined revealed five species (14%) with significant increases; Yellow-bellied Flycatcher, Least Flycatcher, Redbreasted Nuthatch, American Robin, and American Redstart. Six species (17%) had significant decreases: Eastern Wood-Pewee, Ovenbird, Canada Warbler, Scarlet Tanager，Song Sparrow, White-throated Sparrow.• Over 70% of the decreasing species nest on the ground, which is significantly more than would be expected. Ground-nesting species that declined in multiple study areas, such as the White-throated Sparrow, Common Yellowthroat, Black-and-white Warbler, and Ovenbird, warrant closer attention in the future.• Neither increasing nor decreasing species showed a relationship with any particular migration strategy, although no permanent residents declined significantly.• The abundance of many species varied over the survey period but did not show significant increases or decreases. A common thread among many species was a decline in abundance between 1994 and 1996, with an increase from 1996 to 1998. The reason for this pattern is unclear, but it may be related to winter and spring weather.
Breeding bird monitoring in Great Lakes National Forests: 1991-2001
(University of Minnesota Duluth, 2001) Lind, Jim; Danz, Nicholas P; Jones, Malcolm T; Hanowski, JoAnn M; Niemi, Gerald J
• A total of 135, 168, and 133 stands (1,268 survey points) were surveyed for breeding birds in the Chippewa, Superior, and Chequamegon National Forests, respectively. Eleven years of surveys have been completed in the Chippewa and Superior NF, and ten years in the Chequamegon NF. • Breeding bird surveys in the St. Croix region of Minnesota have been conducted over the past ten years at 171 points. Surveys in southeast Minnesota have been conducted over the past seven years at 211 points. • We were able to examine trends in abundance for 77 bird species in at least one of the five study areas. Fifty species in the Chequamegon NF, 49 species in the Chippewa NF, 41 species in the Superior NF, 39 species in the St. Croix region, and 40 species in Southeast Minnesota were tested for population trends. Thirty- five species were also tested for a regional trend (three national forests combined). • Twenty-six species increased significantly (P > 0.05) in at least one study area and 32 species decreased. Two species had highly significant (P < 0.01) increasing trends in multiple study areas, and seven species had highly significant decreasing trends in multiple study areas. Four species had significant increasing regional trends and 11 had decreasing trends. • The most convincing increasing trends were those of the Red-breasted Nuthatch and American Redstart regionally and in the Chippewa NF, Yellow-bellied Sapsuckcer and Yellow-bellied Flycatcher in the Chequamegon NF, the Chestnutsided Warbler in the Chippewa NF, the Northern Parula in the Superior NF, and the Least Flycatcher in the St. Croix region. Eight other species had highly significant trends in southeastern Minnesota, albeit with a shorter time span than the northern sites. • The most convincing decreasing trends are those of the Eastern Wood-Pewee, Winter Wren, Ovenbird, Scarlet Tanager, and Song Sparrow regionally, the Eastern Wood-Pewee in the Chequamegon and Superior NF, the Winter Wren in the Chequamegon NF, the Song Sparrow in the Chippewa NF, the Hermit Thrush in the Chequamegon and Chippewa NF, and the Black-and-white Warbler in the Chequamegon NF, Superior NF and St. Croix region. The Brown-headed Cowbird decreased in southeastern Minnesota during the six years of monitoring there. • The percentage of increasing species in each study area ranged from 13% in St. Croix, MN study area to 28% in Southeast MN. The percentage of decreasing species ranged from 20% in Southeast MN to 31% in the Chippewa NF. Over half the species in each study area had a non-significant trend (P > 0.05). • There are 17 instances where a species showed a significant increase in a particular study area in results from 2000, with no increase noted in 2001, and 11 instances where a species was not increasing in 2000 and is increasing in 2001. Conversely, there are five instances where a decreasing species in a particular study area from 2000 is no longer showing a significant decrease, and 25 instances where a species was not decreasing in 2000 and is decreasing in 2001. • Ten of the 35 species that were tested for a regional trend had similar trends on Breeding Bird Survey routes. One species had an increasing regional trend and an increasing BBS trend, three species had decreasing trends on both, and six species had non-significant trends on both. • When compared to all species tested, ground nesters were more prevalent among decreasing species (33% vs. 48%) and less prevalent among increasing species (33% vs. 19%), however the differences were not statistically significant (P = 0.069). Evidence from other regional studies have demonstrated greater nest predation rates on ground nests near forest edges, as well as a significant increase in the creation of forest edges in recent years. Landscape fragmentation and nest predation may be having negative effects on declining ground-nesters such as the Winter Wren, Hermit Thrush, Black-and-white Warbler, Ovenbird, and Song Sparrow. • Averaged over all study areas, 10.6% of the points have been harvested since the beginning of monitoring, which is about 1% a year. This is comparable to the 4.8% change from mature forest to early-successional types on federally managed forest lands in northeastern Minnesota between 1990 and 1995.
Breeding bird monitoring in Great Lakes National Forests: 1991-2006
(University of Minnesota Duluth, 2007) Etterson, Matthew; Danz, Nicholas P; Lind, Jim; Hanowski, JoAnn M; Niemi, Gerald J
• A total of 132, 133, and 164 stands (1,254 survey points) were surveyed for breeding birds in the Chequamegon, Chippewa, and Superior National Forests (NF), respectively in 2006. Annual surveys have been conducted since 1991 in the Chippewa and Superior NF, and since 1992 in the Chequamegon NF. • Comprehensive surveys of vegetation structure were carried out on 93, 74, and 63 points in the Chequamegon, Chippewa, and Superior NFs, respectively, on over 50 observer-days of sampling. Monitoring personnel on the Chippewa and Superior NFs provided excellent assistance in the coordination and completion of this effort. • Trends in relative abundance were calculated for 72 bird species, including 57 species in the Chequamegon NF, 57 in the Chippewa NF, and 49 in the Superior NF. Thirty-nine species were also tested for a pooled trend by combining data from the three national forests. • A total of 163 species/national forest trends were calculated in 2006 (not including pooled trends), 68 (42%) of which were significant (P ≤ 0.05). Twenty three species increased significantly (P ≤ 0.05) in at least one national forest and 24 species decreased. Eleven species had significant increasing pooled trends and 11 had decreasing trends. Of the 158 species/national forest trends calculated in 2005, 19 (12%) changed in 2006. • The percent of increasing species on each national forest ranged from 9% in the Chequamegon NF, to 25% in the Chippewa NF. The percent of decreasing species ranged from 20% in the Superior NF, to 28% in the Chequamegon NF. • The short-distance migrant guild showed highly significant declines on all national forests. Long-distance migrants also declined on all national forests. Permanent residents increased on the Chippewa and Superior NF and in the pooled NFs, but were stable on the Chequamegon NF. • The ground nesting guild showed highly significant declines on all national forests. Shrub/sub-canopy nesters increased on Chippewa NF, but were stable in Chequamegon and Superior NFs. Canopy nesters increased in Chquamegon NF and cavity-nesters increased in Chippwa and Superior NFs. All nesting guilds showed significant trends in the pooled NFs with increases in shrub/subcanopy-nesters and cavity-nesters and decreases in ground- and canopy-nesters. • The deciduous and mixed forest bird guilds declined on the Chequamegon and Superior NFs and the pooled NFs. The lowland coniferous forest bird guild declined on the Chippewa NF and the pooled NFs. The early-successional bird guild increased on the Chippewa NF and the upland coniferous bird guild increased on the Chippewa and Superior NFs as well as in the pooled NFs. • Evidence from previous regional studies have demonstrated greater nest predation rates on ground nests near forest/clearcut edges, as well as a significant increase in the creation of forest edges in recent years. Increasing amounts of forest edge and nest predation may be having negative effects on declining ground-nesters such as the Winter Wren, Veery, Hermit Thrush, Ovenbird, and White-throated Sparrow. • Of the 1274 survey sites on the three national forests, 15.5% have been at least partially harvested since the beginning of monitoring, which is about 1% a year. This harvest rate is comparable to the documented 4.8% change from mature forest to early-successional types on federally managed forest lands in northeastern Minnesota between 1990 and 1995 (i.e., ~1% annual change). Thus, it appears that management activities on our sample sites are representative of the national forests as a whole, and that the trends we are documenting are probably occurring across the regional landscape. • Many of the declining trends that we have detected appear to be consistent across years instead of being due to a few years with very low or high abundance. One of the main goals of this monitoring program is to identify potential declines of forest bird species, especially for species of conservation concern such as the Eastern Wood-Pewee, Winter Wren, Hermit Thrush, Ovenbird, and White-throated Sparrow. The declines observed over the past years for common species such as the Ovenbird and White-throated Sparrow are a continuing concern and special management consideration should be given to these species.
Breeding Birds of the Cornish Hardwood Management Area: Aitkin County, Minnesota
(University of Minnesota Duluth, 1998) Hanowski, JoAnn M
The Cornish Hardwood management area (CHMA), located in northeast Aitkin County is managed by Aitkin County forestry department and Minnesota Department of Natural Resources in an uneven-aged format. The forestry goals for this area are to provide wood resources for local industry and to promote regeneration and growth of high value hardwood trees by maintaining this forest type throughout each rotation. Northern hardwood forests provide habitat for a variety of breeding bird species, including several long-distant migrants. Although, response of breeding birds to successional forest stages from clearcut to mature stand ages are relatively well known and predictable for northern Minnesota forests, breeding bird response to uneven-aged management in northern hardwoods has not been studied in Minnesota. Our objectives were to: 1) establish a long-term breeding bird monitoring program in the CHMA to detect annual changes in species abundances, 2) determine whether bird community composition and species abundances are affected by uneven-aged management, and 3) compare bird community in the CHMA with other northern hardwood stands in northern Minnesota. Twenty-six individual stands that were greater than 40 acres were selected for monitoring. Eight stands were harvested within the past 10 years (managed), eight stands are in the management area, but have not been recently managed (unmanaged), and ten sites were located in Savannah Portage State Park. One breeding bird survey was conducted at each point with an unlimited radius 10 minute count point count. A total of 25 bird species were observed in 26 stands (52 points). On average, we observed about 22 individuals and 7 to 8 species in each stand (total of two point counts). No differences were detected in bird communities among management types. Two of the 15 species tested with analysis of variance indicated a significant difference (P < 0.05) in abundance among management types. The Chestnut-sided Warbler and Winter Wren were more abundant in the managed than in the unmanaged or reference sites. Both of these species are associated with habitat features that occur shortly after forest management activities (shrubs or slash piles). A cluster analysis with bird species showed that bird community composition was not different among management types. Overall bird communities in all stands sampled regardless of management history were similar. This result indicates that uneven-aged management such as the type that has been lone at CHMA does not result in a forest structure that is different than what currently exists in other northern hardwood stands in this region. This result is similar to what we have found previously for other “old-growth” northern hardwood stands in the State. A species that was absent in northern hardwood stands in this region was the Black-throated Blue Warbler. This species is rarely found in northern hardwoods in north central Minnesota but occurs in selected northern hardwood stands in northeast Minnesota, primarily in the Lake Superior highlands. A study on the Black-throated Blue Warbler in northeast Minnesota in 1998 found that the species prefers northern hardwood stands with a shrub understory. In areas where there are few shrubs, the species was primarily associated with small gaps (in the range of 0.05 to 0.10 ha) in the canopy that have resulted from blowdowns. The natural disturbance regime for northern hardwoods in this region was windstorms which occur every few decades and create small forest gaps by blowing down senescent or weak and hollow trees. It is possible that the Black-throated Blue Warbler historically responded to habitat that was created by these gaps and moved across the landscape as new patches were created and old patches became unsuitable. It may be possible maintain the objectives for forest management in the CHMA by completing harvests that would result in the creation of small gaps. Another recommendation would be to chose harvest equipment that would have less impact on the understory vegetation (e.g., result in less skidding of trees). These management suggestions will not only provide more suitable habitat for avian species that require shrubs and saplings, but also a population of seedlings and saplings for future recruitment into the canopy.
Breeding Birds of the Cornish Hardwood Management Area: Aitkin County, Minnesota 1998-1999
(University of Minnesota Duluth, 1999) Hanowski, JoAnn M
Breeding bird surveys were conducted for the second consecutive year in the Cornish Hardwood management area (CHMA), located in northeast Aitkin County. The objectives of this project are to: 1) establish a long-term breeding bird monitoring program in the CHMA to detect annual changes in species abundances, 2) determine whether bird community composition and species abundances are affected by uneven-aged management, and 3) compare the bird community in the CHMA with other northern hardwood stands in northern Minnesota. This report provides a summary of bird surveys completed in June of 1999 and also compares 1998 and 1999 survey results. Please refer to the 1998 report for more detail on methods and rationale for this study. Twenty-six individual stands that were greater than 40 acres were selected for monitoring. Eight stands were harvested within the past 10 years (managed), eight stands are in the management area, but have not been recently managed (unmanaged), and ten sites were located in Savannah Portage State Park. One breeding bird survey was conducted at each point with an unlimited radius 10 minute count point count in Junes of 1998 and 1999. A total of 25 bird species were observed in 26 stands (52 points) in 1998 and 32 species were counted in 1999. Over both years, a total of 37 species have been observed in this area. On average, we observed about 22 individuals and 7 to 8 species in each stand (total of two point counts) in 1998 and a slightly higher number, about 25 individuals and 8 species in 1999. Results of a two-way analysis of variance for the bird community variables indicated that more (P < 0.001) total individuals were observed in 1999 than in 1998. In addition, we found a significant difference in number of species observed in stands with different management history. Here, unmanaged stands had fewer species (P < 0.01) than the managed or reference stands. Not one of the 8 species tested with two-way analysis of variance indicated a significant difference (P < 0.05) in abundance among management types or year. We found a significant interaction for year and treatment for the Scarlet Tanager. This test result indicated that the species abundance pattern on unmanaged sites was not consistent between 1998 and 1999. For example, more Scarlet Tanagers were observed on unmanaged sites in 1998 than in the other two management groups, but in 1999, this management type had the fewest number of individuals of this species. A cluster analysis with bird species showed that bird community composition was not different among management types or between years. Occurrence of uncommon species on individual sites was most likely the reason why some sites differed in their relative cluster position (or composition of cluster) between the two years. A species that was absent in northern hardwood stands in this region in 1998 but present in 1999 was the Black-throated Blue Warbler. This species is rarely found in northern hardwoods in north central Minnesota but occurs in selected northern hardwood stands in northeast Minnesota, primarily in the Lake Superior highlands. A recently completed study on the Black-throated Blue Warbler in northeast Minnesota applied in managing in 1999 will provide quantitative habitat information for this species that could be the CHMA for this hardwood dependent species.
Breeding Birds of the Cornish Hardwood Management Area: Aitkin County, Minnesota 1998-2000
(University of Minnesota Duluth, 2000) Hanowski, JoAnn M
Breeding bird surveys were conducted for the third consecutive year in the Cornish Hardwood management area (CHMA), located in northeast Aitkin County. The objectives of this project are to: 1) establish a long-term breeding bird monitoring program in the CHMA to detect annual changes in species abundances, 2) determine whether bird community composition and species abundances are affected by uneven-aged management, and 3) compare the bird community in the CHMA with other northern hardwood stands in northern Minnesota. This report provides a summary of bird surveys completed in June of 2000 and also compares 1998, 1999 and 2000 survey results.
ELF Communications System Ecological Monitoring Program: Bird Species and Communities Wisconsin Test Facility: Final Report
(University of Minnesota Duluth, 1990) Hanowski, JoAnn M; Blake, John G.; Niemi, Gerald J; Collins, Patrick T
This report summarizes work completed in our study that was designed to isolate effects of electromagnetic (EM) fields produced by extremely low frequency (ELF) antenna systems on bird species breeding in or migrating through Wisconsin. Specifically, we wanted to determine if bird species richness and abundance differed between areas that were close to the antenna and those that were far enough away to be unaffected by the antenna. Characteristics examined included total species richness and abundance, abundances of common bird species, and abundances of birds within selected guilds. Vegetation was measured to identify differences and similarities between control and treatment areas and habitat variables were used in analysis of covariance (ANCOVA) to compare abundant bird species’ numbers between control and treatment areas after they were adjusted for habitat differences. We found no consistent patterns that would demonstrate that birds were either attracted to or repelled by EM fields produced by the antenna. Most differences in abundance between control and treatment areas could be attributed to habitat differences (both in ANCOVA and guild analysis). Based on tests of transects paired by habitat similarities, the presence of the antenna ROW may have affected abundance of some bird species in the study areas. Abundance of species related to edges was higher in treatment areas particularly during May and June. Differences in abundance of individuals that require forest interiors between control and treatment areas were not as pronounced. Because we have no before data in Wisconsin, we cannot exclude the possibility that these differences between control and treatment existed before the ROW was cut, such comparisons, however will be possible in Michigan.
ELF Communications System Ecological Monitoring Program: Bird Species and Communities: Annual Report 1987
(University of Minnesota Duluth, 1988) Blake, John G.; Hanowski, JoAnn M; Niemi, Gerald J
This investigation was designed to isolate effects of electromagnetic fields produced by ELF antenna systems on bird species breeding in or migrating through Wisconsin and Michigan. Specifically, we seek to determine if bird species richness and abundance differ between areas that are close to the antenna and those that are far enough away to be unaffected by the antenna. We are pursuing this question at both the community and species level. Characteristics examined include total species richness and abundance, abundances of common bird species, and abundances of birds within selected guilds (based on habitat, diet, migration strategy, and nesting behavior). This report summarizes 1987 research activities for studies to identify potential effects of ELF electromagnetic fields on bird species and communities in Wisconsin and Michigan. Our monitoring program included bird censuses over a five month period from May to September. In addition, we completed a detailed habitat assessment of all control and treatment segments in Wisconsin that was initiated in 1986. These data will allow us to pair control and treatment segments on the basis of habitat, thereby enabling us to assess effects of the ELF antenna, even though there are no pre-impact data available from Wisconsin. The Michigan transmitter operated intermittently at low levels during 1987. We are therefore considering 1987 a transitional year in terms of EM exposures. Principal components (PCA) and Bray-Curtis analyses of vegetation on Wisconsin segments revealed differences between treatment and control segments. Qualitative assessments of habitat types in Michigan also revealed differences between segment types. The most X important difference in relation to birds relates to distribution of coniferous and deciduous habitats. Treatment segments support more coniferous and lowland habitats than do control areas in both states. Logging affected the vegetation on four treatment segments in Michigan and four treatment and one control segment in Wisconsin. In Michigan, clear-cutting along several treatment segments resulted in a significant difference between treatment and control segments in the amount of early successional habitat, with more now present on treatment sites. Logging was less severe in Wisconsin but did result in significant changes in some habitat variables for the affected segments. We omitted all segments affected by logging in our between year comparisons of bird communities. Five segments sampled for vegetation in Wisconsin in 1986 were resampled in 1987. Between year differences were noted for seven variables, especially ground cover, canopy cover, and overall height of the vegetation. Measurement of these variables involves some qualitative estimations and between year differences may be due to sampling effects. These variables were not included in PCA. Bird abundance and species diversity were highest in June and July in Michigan and in May and June in Wisconsin. Observations reached a low in September in Michigan but increased from August to September in Wisconsin. Differences between treatment and control segments in total number of individuals and species were not consistent across seasons in either state. Species richness was higher on control than on treatment segments in Michigan in May; no other differences in community level parameters were significant in either state. Considerable annual variation in numbers of individuals and species was noted, particularly in Michigan, where significant year effects occurred in four of five sample periods. Annual differences were not, however, consistent among seasons in Michigan. Particularly abundant species (all seasons included) included the Nashville Warbler, Ovenbird, White-throated Sparrow, Red-eyed Vireo, Black-capped Chickadee, Golden-crowned Kinglet, and Red-breasted Nuthatch. The most abundant species present on treatment and control segments varied among seasons and between states. Among "abundant" species (>1 individual observed/ 500 m segment), seven comparisons (over all seasons) revealed a significant difference between treatment and control segments in Michigan; five indicated a greater abundance on treatment segments. Three comparisons indicated a higher abundance on treatment segments in Wisconsin and two on controls. Twelve comparisons in Michigan and eight in Wisconsin showed significant annual variation in abundance. Twenty-one comparisons of common species (based on prominence values) between treatment and control segments in Michigan and 14 in Wisconsin were significant. Values were higher on control segments in Michigan in all but two cases; 9 of 14 were more abundant on control segments in Wisconsin. Few species were consistently and significantly more abundant on either treatment or control segments among seasons within a year or within seasons between years. Differences between treatment and control segments, particularly in Michigan where the antenna was operated periodically, are most likely due to habitat differences. Species were classified into guilds on the basis of migratory strategy, nest site preference, diet and foraging location, and preferred breeding habitat. Abundances of different guild types on treatment and control segments were compared for June 1985, 1986, and 1987, the primary breeding season. Few significant differences were found between treatment and control segments and most were not consistent among years. Differences were most consistent for habitat categories, suggesting that habitat differences between treatment and control segments may be responsible for many of the observed differences in bird distribution patterns. We repeated tests for differences in abilities of observers to detect birds, for differences in spring arrival times of several different groups of birds, and for potential edge effects on distribution patterns of birds. Few significant differences emerged.
ELF Communications System Ecological Monitoring Program: Bird Species and Communities: Annual Report 1988-1989
(University of Minnesota Duluth, 1989) Niemi, Gerald J; Hanowski, JoAnn M
This investigation was designed to isolate effects of electromagnetic (EM) fields produced by extremely low frequency (ELF) antenna systems on bird species breeding in or migrating through Wisconsin and Michigan. Specifically, we seek to determine if bird species richness and abundance differ between areas that are close to the antenna and those that are far enough away to be unaffected by the antenna. We are pursuing this question at both the community and species level. Characteristics examined include total species richness and abundance, abundances of common bird species, and abundances of birds within selected guilds. Our monitoring program includes bird censuses over a five month period from May to September (1986-1989). Additional data were collected in June of 1985 and August-September of 1984. Here we summarize results of our 1989 research activities. The Michigan transmitter began 150 amp tuning and testing intermittently in the first part of May. On the 14th of May, the transmitter began continuous 150 amp operation for 16 hrs/day on weekdays and all day on weekends. On October 7th, the Michigan transmitter began full power continuous operation. We therefore consider May 1989 to be a transitional period, and June through September to be impact periods. Bird abundance and species diversity were highest in June and July in Michigan and in May and June in Wisconsin. No significant differences in community level parameters (total individuals, total species) were noted in either state. Considerable annual variation in numbers of individuals and species was noted. Particularly abundant species (all seasons included) included the Nashville Warbler, Ovenbird, White-throated Sparrow, Red-eyed Vireo, Black-capped Chickadee, Hermit Thrush and Golden-crowned Kinglet. The most abundant species present on treatment and control segments varied among seasons and between states. Among "abundant" species (>1 individual observed/500 m segment), five of 34 comparisons (over all seasons) revealed a significant difference between treatment and control XII segments in Michigan; four indicated a greater abundance on control segments. Six of 31 comparisons indicated a significant difference between treatment and control segments in Wisconsin; four indicated a greater abundance on control segments. Previous analyses of vegetation on Wisconsin and Michigan study sites (Blake et al. 1988) revealed differences between treatment and control plots. The difference most likely to influence bird populations was distribution of coniferous and deciduous habitats. Treatment segments supported more coniferous and lowland habitats than did control areas, in both states. To account for differences in habitat between treatment and control segments in Wisconsin, we paired treatment and control segments on the basis of habitat similarity and compared bird abundances on these paired segments (N = 15 pairs). (The Michigan study is designed as a "before-and-after" experiment and, thus, differences in habitat pose less of a problem for interpretation of bird distribution patterns.) Two of 31 comparisons of abundant species showed significant differences between paired segments in Wisconsin; in both cases, numbers were higher on treatment segments. The final report for Wisconsin will consider effects of vegetation on results from previous years and on distribution patterns of guilds. Eighteen of 105 comparisons of common species (based on prominence values) between treatment and control segments (all segments) in Michigan and 20 of 100 in Wisconsin were significant. Values were higher on control segments in Michigan in 9 cases; 6 of 20 were more abundant on control than on treatment segments in Wisconsin. Few species were consistently and significantly more abundant on either treatment or control segments among seasons within a year or within seasons between years. Differences between treatment and control segments are most likely due to habitat differences. Species were classified into guilds on the basis of foraging behavior and preferred breeding habitat. Few significant differences in abundances of birds within different guilds were found between treatment and control segments. Differences were most consistent for habitat categories, providing further evidence that habitat differences are responsible for many of the observed differences in bird distribution patterns between treatment and control segments.
ELF Communications System Ecological Monitoring Program: Bird Species and Communities: Annual Report 1989-1990
(University of Minnesota Duluth, 1990) Blake, John G.; Niemi, Gerald J; Hanowski, JoAnn M; Collins, Patrick T
This investigation was designed to isolate effects of electromagnetic (EM) fields produced by extremely low frequency (ELF) antenna systems on bird species breeding in or migrating through Wisconsin and Michigan. Specifically, we seek to determine if bird species richness and abundance differ between areas that are close to the antenna and those that are far enough away to be unaffected by the antenna. We are pursuing this question at both the community and species level. Characteristics examined include total species richness and abundance, abundances of common bird species, and abundances of birds within selected guilds. Our monitoring program has included bird censuses over a five month period from May to September (1986-1989). Additional data were collected in both states in August-September of 1984 and June of 1985. Research in Wisconsin was completed in 1989 but has continued in Michigan. A final report summarizing work in Wisconsin has been completed (Hanowski et al. in press). Here we summarize results of our 1990 research activities in Michigan. The Michigan transmitter began 150 amp tuning and testing intermittently in the first part of May 1989. On 14 May, the transmitter began continuous 150 amp operation for 16 hrs/day on weekdays and all day on weekends. On 7 October 1989, the Michigan transmitter began continuous operation at full power. We therefore consider 1990 to be the first full impact year. Overall, bird abundance and species diversity were highest and approximately the same during May, June, and July. Species diversity was significantly greater on control areas during June and September, but no other differences in community level parameters were significant. Considerable annual variation in numbers of individuals and species was noted. Particularly abundant species (all seasons included) included the Ovenbird, Black-capped Chickadee, and Nashville Warbler. Other common species included Red-eyed Vireo, White-throated Sparrow, Golden-crowned Kinglet, Hermit Thrush, and Black-throated Green Warbler. The most abundant species present on treatment and control segments varied among seasons. Among "abundant" species (>1 individual observed/500 m segment), five of 24 comparisons (21%; all seasons combined) revealed a significant difference between treatment and control segments in Michigan; two indicated a greater abundance on control segments. Previous analyses of vegetation on Michigan study sites (Blake et al. 1988) revealed differences between treatment and control plots. The difference most likely to influence bird populations was distribution of coniferous and deciduous habitats. Treatment segments supported more coniferous and lowland habitats than did control segments. It is important to note that habitat differences that exist between treatment and control areas will not affect our analysis of antenna effects. The Michigan study is designed as a before-and-after experiment; we can compare changes in bird abundance over time on treatment segments and on control segments. If electromagnetic fields produced by antenna operation affect bird distribution patterns, we expect to detect a change in patterns of abundance between treatment and control areas. Such changes, if they occur, would be independent of already present habitat differences. Seventeen of 114 comparisons (15%) of common species (based on prominence values, see page 7) between treatment and control segments (all segments) in Michigan were significant. Values were higher on control segments in 10 cases. Few species were consistently and significantly more abundant on either treatment or control segments among seasons within a year or within seasons among years. Differences between treatment and control segments were most likely due to habitat differences. Species were classified into guilds on the basis of foraging behavior and preferred breeding habitat. Few significant differences in abundance of birds within different guilds were found between treatment and control segments. Differences were most consistent for habitat categories (e.g., birds that prefer deciduous forest were more abundant on control segments in 4 of 5 months), providing further evidence that habitat differences were responsible for many of the observed differences in bird distribution patterns between treatment and control segments.
ELF Communications System Ecological Monitoring Program: Bird Species and Communities: Annual Report 1991
(University of Minnesota Duluth, 1991) Blake, John G.; Niemi, Gerald J; Hanowski, JoAnn M; Collins, Patrick T
This investigation was designed to isolate effects of electromagnetic (EM) fields produced by extremely low frequency (ELF) antenna systems on bird species breeding in or migrating through Wisconsin and Michigan. Specifically, we seek to determine if bird species richness and abundance differ between areas that are close to the antenna and those that are far enough away to be unaffected by the antenna. We are pursuing this question at both the community and species level. Characteristics examined include total species richness and abundance, abundances of common bird species, and abundances of birds within selected guilds. Our monitoring program has included bird censuses in both states over a five month period from May to September, 1986-1991. Additional data were collected in August-September 1984 and in June 1985, in both states. Bird censuses were terminated in Wisconsin after 1989 but are continuing in Michigan. No consistent patterns have yet emerged to demonstrate that birds are more or less abundant on treatment relative to control segments in either state after effects of habitat are accounted for. Further, few significant differences have been found at the community or species level; differences in one season or year are not always repeated in subsequent years or seasons. Most differences that exist between treatment and control transects can be attributed to habitat differences or chance rather than to electromagnetic field differences.

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