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A survey of bluff forest avifauna in Southwestern Illinois.

INTRODUCTION

The forested bluffs of southwestern Illinois attract large numbers of migrating songbirds due to their prime location near the confluence of the Mississippi, Missouri, and Illinois Rivers. These once extensive oak-hickory forests are now highly fragmented, initially due to agriculture and more recently due to increasing urbanization. As the St. Louis metropolitan area continues its rapid expansion eastward, protection and management of remaining forests is crucial. The campus of Southern Illinois University Edwardsville (SIUE) and adjacent Bohm Woods Nature Preserve include some of the largest remaining forest tracts in Madison County, Illinois.

Population declines have been noted for many neotropical migrants in Illinois (Robinson et al., 1995), and are hypothesized to be influenced by fragmentation of forests on breeding grounds (Gates and Evans, 1998; Robinson and Robinson, 2001), brood parasitism by Brown-headed Cowbirds (Robinson et al, 1995), deforestation in the tropics (Bollinger and Linder, 1994), invasion of exotic plants and increasing populations of browsers (Elphick et al., 2001) and predators (Heske et al., 2001). Our objective was to assess avian populations in several forest patches in southwestern Illinois in order to characterize existing habitat as well as to inform future land use decisions in this rapidly developing area.

The three forest patches included in the survey occur on or adjacent to the SIUE campus in Madison County, Illinois (Fig. 1). All occur on loess bluffs at the edge of the Mississippi River floodplain known as the American Bottoms. Sweet William Woods is the largest forest patch covering 59.7 ha. The majority of this mesic/dry-mesic upland forest was formerly agricultural land that has experienced recent regrowth (<50 years). Portions of the forest that are along ravines have had trees present for over 100 years. Sweet William Woods includes an extensive network of trails and experiences the greatest amount of foot traffic. Bluebell Woods is a smaller mesic/dry-mesic upland forest that covers 30.3 ha and has a similar history of disturbance. However, it lacks trails and experiences little foot traffic. Bohm Woods Nature Preserve is largely mesic/dry-mesic upland forest, but also includes portions of wet bottomland forest. It covers 25.6 ha and has a more uniform distribution of mature trees than the other two forest patches. In addition, it has had little logging disturbance and receives intermediate levels of human traffic. All three forests have abundant deer populations due to adjoining agricultural land coupled with minimal hunting pressure.

MATERIALS AND METHODS

Fixed-distance point-count surveys (25 m radius) were conducted from May-July, 2008 at 129 randomized plots on the SIUE campus and adjacent Bohm Woods Nature Preserve (Bluebell, n = 34; Bohm, n = 29; Sweet William, n = 66). Surveys were conducted daily from 0600-1000 hours except when raining, foggy, or excessively windy. Each survey included a 1 minute warm-up period, followed by a 5 minute sampling period. Before the warm-up period a laser rangefinder (Bushnell Yardage Pro 500) was used to mark distance in the 4 cardinal directions (unless prevented by vegetation). All birds seen or heard during the sampling period were recorded, but only species within the 25 m radius were used in population density estimates (Bibby et al., 2000). During the sampling period a digital voice recorder (Olympus DS-40) was used to record songs and calls for subsequent identification in the lab. Sites were chosen each day to maximize distance between sampling locations, and the most direct routes to those sites were traveled in order to minimize disturbance (Bibby et al., 2000). Plots were visited 3 times each for a total sampling effort of 32.25 hours.

Density estimates for each bird species assumed there was one female for each singing male recorded. Densities were then calculated within plots and scaled up to one hectare. Overall densities for each forest patch were summed across all plots and average densities were estimated. In addition, species richness (S; total number of species), Shannon's diversity index (H'loge; measure of diversity incorporating richness and evenness), and Hill's diversity index (N1; exponential of H'loge) were calculated for each forest patch using Primer 6 (Clarke and Gorley, 2008). Indicator species analysis (ISA) was used to identify bird species that best characterized each forest patch (Dufrene and Legendre, 1997). We used a liberal P-value of 0.2 for ISA since we intended it as an exploratory analysis rather than as an explicit test of hypotheses.

RESULTS

Species richness was highest for the largest forest patch, Sweet William Woods (S = 63), with Bluebell and Bohm Woods exhibiting identical richness (S = 45; Table 1). Species diversity, as measured by Shannon's diversity index, was similar between Sweet William (H'(loge) = 3.39) and Bohm Woods (H'(loge) = 3.38), despite a large difference in area. Bluebell Woods (30.3 ha) had the lowest species diversity (H'(loge) = 3.16; Table 1).

Tables 2-5 list the densities for each species within each forest patch. Overall, warbler population densities were relatively low throughout the three forest patches (<1 individual/ha; Table 2). Exceptions, included Northern Parula, which was abundant (>2 /ha) at all three sites, and Magnolia, Yellow, and Black-throated Green Warblers, which were moderately abundant in Bohm Woods (1-2 individuals/ha). Among other migratory passerines, densities exceeded 1 individual/ha at all three sites for Eastern Wood-Pewee, Acadian Flycatcher, Wood Thrush, Great Crested Flycatcher, Indigo Bunting, Blue-gray Gnatcatcher, and Red-eyed Vireo (Table 3). In addition, Swainson's Thrush and White-throated Sparrow were abundant in Bohm Woods. Among resident passerines, Tufted Titmouse, Northern Cardinal, American Goldfinch, Brown-headed Cowbird, Eastern Towhee, Carolina Chickadee, White-breasted Nuthatch, Carolina Wren, and American Robin were abundant at all three sites. The Blue Jay was abundant at Bluebell and Sweet William Woods. (Table 4). Among nonpasserines, Red-bellied and Downy Woodpeckers were abundant at all three sites; whereas, Ruby-throated Hummingbird, Chimney Swift, Northern Flicker, and Hairy Woodpecker were abundant at Bohm Woods (Table 5).

Table 6 describes the results of the indicator species analysis (ISA). Seven species were identified whose relatively high indicator values acted to differentiate Bluebell Woods from the remaining forest patches. These included Northern Cardinal, American Goldfinch, Tufted Titmouse, Eastern Towhee, Blue-gray Gnatcatcher, Common Grackle, and Black-capped Chickadee. Three species differentiated Sweet William from the other forests: Carolina Chickadee, Carolina Wren, and Kentucky Warbler. Lastly, 12 species served as indicators for Bohm Woods: Acadian Flycatcher, American Robin, Ruby-throated Hummingbird, Downy woodpecker, Wood Thrush, Hairy Woodpecker, Chimney Swift, Northern Flicker, Yellow Warbler, White-throated Sparrow, Black-throated Green Warbler, and Swainson's Thrush.

Table 7 lists additional species encountered during the sampling period outside of 25 m plots and not included in species richness or density estimates. Table 8 lists additional species encountered outside of the sampling period and not included in species richness or density.

DISCUSSION

We identified 90 species among three forest patches on and adjacent to the Southern Illinois University Edwardsville campus, including species of conservation concern such as the state threatened Black-billed Cuckoo (proposed) and the state endangered Northern Harrier. Bohm Woods appears to be particularly valuable from a conservation perspective. It is the only patch to feature migratory transients as indicator species, including Black-throated Green Warbler and Swainson's Thrush (Table 6). This suggests an important role as a migratory stopover site, despite its small size. Nevertheless, Bohm Woods is also comprised of relatively undisturbed mature forest which may make it more attractive than larger forest patches with greater levels of disturbance. In addition, Bohm Woods is also distinguished by supporting higher numbers of forest interior species, including two Neotropical migrants sensitive to fragmentation, Acadian Flycatcher and Wood Thrush (Roth et al., 1996; Whitehead and Taylor, 2002; Table 6).

The Acadian Flycatcher breeds near water in deciduous forests of the Midwest (Whitehead and Taylor, 2002). They have been found to exhibit low reproductive success within 600 m of a forest edge in southern Illinois due to cowbird parasitism and predation resulting from fragmentation (Hoover et al., 2006). None of the forest patches surveyed in the present study include habitat greater than 600 m from an edge. This would seem to make the entire area a population sink for Acadian Flycatchers. However, another study in Illinois determined that Acadian Flycatchers may be less sensitive to fragmentation than other forest passerines in Illinois and may exhibit reproductive success in narrow riparian corridors (Chapa-Vargas and Robinson, 2007). The extensive network of ravines, transitioning to wet, bottomland forest in Bohm Woods may provide ideal conditions for Acadian Flycatchers, as evidenced by the high density estimates (6.79/ha; Table 6). The degree of reproductive success should be monitored to determine which of these two scenarios characterizes this population.

Wood Thrushes in Illinois also exhibit low nesting productivity due to the effects of forest fragmentation. Forest patches as large as 2200 ha have been found to be population sinks (Trine, 1998). Given the small size of the forest patches in the present study, local populations are likely to exhibit low recruitment. Nevertheless, Bohm Woods attracts relatively large numbers of Wood Thrush due to its mature trees. Despite its likely status as a population sink, it undoubtedly has value as a migratory stopover site.

Bohm Woods exhibited the lowest Brown-headed Cowbird density of the three forest patches (Table 4). Brown-headed Cowbirds are brood parasites that lay their eggs in the nests of many avian host species, providing no additional parental investment. The hosts may then incubate and rear cowbird offspring to the detriment of their own fitness (Brittingham and Temple, 1983). Cowbirds forage in agricultural areas and are typically more abundant at forest edge rather than forest interior (Lowther, 1993). Despite its small size and close proximity to agriculture, Bohm Woods may be less attractive to cowbirds than larger surrounding patches due to its mature trees and circular shape, which maximizes the amount of interior forest habitat.

Sweet William and Bluebell Woods are comprised of large areas of regrowth and are characterized by higher numbers of bird species associated with this habitat type (Table 6). However, they maintain core areas of mature trees, concentrated around ravines. These areas are important for forest interior bird species and should be protected from future disturbance. As the surrounding forest continues to mature, the value for interior species will increase.

Efforts should be made to acquire additional land and convert adjacent non-forested land to forest in order to benefit forest interior species. Although, young forest would be of little direct value to these species in terms of suitable foraging or nesting habitat, it would serve an important indirect role by providing a buffer to cowbirds and predators. This is critical for Bohm Woods which has higher numbers of sensitive species.

Bluff forest avifauna should continue to be observed over the long term in order to monitor population trends. This is especially important due to current and predicted changes in vegetation. Long-term monitoring may allow elucidation of the effects of rapid expansion of bush honeysuckle (Lonicera maackii), as well as the predicted loss of ash (Fraxinus sp.) from these forests. The plots used in this study are permanently marked and georeferenced and we intend to resample them regularly in the future to monitor changes in the vegetation and bird communities.

ACKNOWLEDGMENTS

This is contribution number 30 of the National Great Rivers Research and Education Center. We thank the Illinois Nature Preserves Commission for permission to conduct research in Bohm Woods Nature Preserve. We thank David Hartweger, Jerrod Looft, and Felicia Scaggs for assistance with establishing research plots and Bill Retzlaff for loaning the rangefinder. This research was supported in part by grants from the National Great Rivers Research and Education Center, the Illinois Department of Natural Resources Wildlife Preservation Fund and the Illinois Ornithological Society/Du Page Birding Club.

[FIGURE 1 OMITTED]

received 8/24/09

accepted 1/16/10

LITERATURE CITED

Bibby, C.J., N.D. Burgess, D.A. Hill, and S.H. Mustoe. 2000. Bird Census Techniques. Academic Press, London, 302pp.

Bollinger, E.K., and E.T. Linder. 1994. Reproductive success of neotropical migrants in a fragmented Illinois forest. Wilson Bulletin 106(1): 46-54.

Brittingham, M.C. and S.A Temple. 1983. Have cowbirds caused forest songbirds to decline? Bioscience 33(1): 31-35.

Chapa-Vargas, L., and S.K. Robinson. 2006. Nesting success of a songbird in a complex floodplain forest landscape in Illinois, USA: local fragmentation vs. vegetation structure. Landscape Ecology 21:525-537.

Clarke K.R., and R.N. Gorley. 2008. Primer v6. Roborough, Plymouth, UK: Plymouth Marine Laboratory.

Dufrene, M. and P. Legendre. 1997. Species assemblages and indicator species: the need for a flexible asymmetrical approach. Ecological Monographs 67:345-366.

Elphick, C., J.B. Dunning Jr., and D.A. Sibley. 2001. The Sibley Guide to Bird Life and Behavior. Alfred A. Knopf, New York. 587.

Gates, J.E., and D.R. Evans. 1998. Cowbirds breeding in the Central Appalachians: spatial and temporal patterns and habitat selection. Ecological Applications 8:27-40.

Heske, E.J., S.K. Robinson, and J.D. Brawn. 2001. Nest predation and neotropical migrant songbirds: piecing together the fragments. Wildlife Society Bulletin 29:52-61.

Hoover, J. P., T.H. Tear, and M.E. Baltz. 2006. Edge effects reduce the nesting success of Acadian Flycatchers in a moderately fragmented forest. Journal of Field Ornithology 77:425-236.

Lowther, P.E. 1993. Brown-headed Cowbird (Molothrus ater), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/047.

Robinson, S.K., and W.D. Robinson. 2001. Avian nesting success in a selectively harvested north temperate deciduous forest. Conservation Biology 15:1763-1771.

Robinson, S.K., F.R. Thompson III, T.M. Donovan, D.R. Whitehead, J. Faaborg. 1995. Regional forest fragmentation and the nesting success of migratory birds. Science 267:1987-1990.

Roth, R.R., M.S. Johnson, and T.J. Underwood. 1996. Wood Thrush (Hylocichla mustelina), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/246.

Trine, C.L. 1998. Wood thrush population sinks and implications for the scale of regional conservation strategies. Conservation Biology 12:576-585.

Whitehead, D.R. and T. Taylor. 2002. Acadian Flycatcher (Empidonax virescens), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/614.

Lane A. Richter, Richard L. Essner, Jr., and Peter R. Minchin Department of Biological Sciences Southern Illinois University Edwardsville, IL 62026, USA Correspondence: ressner@siue.edu
Table 1. Species richness (S), Shannon (H' loge) and Hill (N1)
diversity indices for 3 forest patches in Madison County,
Illinois.

Forest            S    H'([log.sub.e])    N1

Bluebell          45        3.16         23.6
Bohm              45        3.38         29.5
Sweet William     63        3.39         29.6

Table 2. Estimated population densities (individuals/ha) for
warblers in 3 forest patches in Madison County, IL

Species                   Common Name

Dendroica coronata        Yellow-rumped Warbler
Dendroica dominica        Yellow-throated Warbler
Dendroica fusca           Blackburnian Warbler
Dendroica magnolia        Magnolia Warbler
Dendroica pensylvanica    Chestnut-sided Warbler
Dendroica petechia        Yellow Warbler
Dendroica striata         Blackpoll Warbler
Dendroica virens          Black-throated Green Warbler
Geothlypis trichas        Common Yellowthroat
Mniotilta varia           Black-and-white Warbler
Oporornis formosus        Kentucky Warbler
Oporornis philadelphia    Mourning Warbler
Parula americana          Northern Parula
Seiurus aurocapilla       Ovenbird
Seiurus motacilla         Louisiana Waterthrush
Setophaga ruticilla       American Redstart
Vermivora peregrina       Tennessee Warbler
Vermivora ruficapilla     Nashville Warbler
Wilsonia citrina          Hooded Warbler

Species                   Bluebell   Bohm   Sweet William

Dendroica coronata          0.60     0.34       0.15
Dendroica dominica          0.00     0.34       0.15
Dendroica fusca             0.30     0.00       0.15
Dendroica magnolia          0.30     1.02       0.23
Dendroica pensylvanica      0.00     0.85       0.62
Dendroica petechia          0.00     1.53       0.31
Dendroica striata           0.00     0.00       0.46
Dendroica virens            0.00     1.02       0.15
Geothlypis trichas          0.60     0.00       0.15
Mniotilta varia             0.00     0.00       0.15
Oporornis formosus          0.00     0.00       0.39
Oporornis philadelphia      0.00     0.17       0.00
Parula americana            4.19     2.55       3.70
Seiurus aurocapilla         0.00     0.34       0.31
Seiurus motacilla           0.00     0.00       0.46
Setophaga ruticilla         0.30     0.51       0.39
Vermivora peregrina         0.30     0.34       0.31
Vermivora ruficapilla       0.00     0.00       0.15
Wilsonia citrina            0.00     0.34       0.00

Table 3. Estimated population densities (individuals/ha) for
other (non-warbler)  migratory passerines in 3 forest patches in
Madison County, IL.

Species                    Common Name

Catharus fuscescens        Veery
Catharus ustulatus         Swainson's Thrush
Contopus virens            Eastern Wood-Pewee
Dumetella carolinensis     Gray Catbird
Empidonax alnorum          Alder Flycatcher
Empidonax flaviventris     Yellow-bellied Flycatcher
Empidonax virescens        Acadian Flycatcher
Hylocichla mustelina       Wood Thrush
Icterus galbula            Baltimore Oriole
Myiarchus crinitus         Great Crested Flycatcher
Passerina cyanea           Indigo Bunting
Pheucticus ludovicianus    Rose-breasted Grosbeak
Piranga olivacea           Scarlet Tanager
Piranga rubra              Summer Tanager
Polioptila caerulea        Blue-gray Gnatcatcher
Sayornis phoebe            Eastern Phoebe
Spizella passerine         Chipping Sparrow
Toxostoma rufum            Brown Thrasher
Troglodytes aedon          House Wren
Tyrannus tyrannus          Eastern Kingbird
Vireo flavifrons           Yellow-throated Vireo
Vireo gilvus               Warbling Vireo
Vireo griseus              White-eyed Vireo
Vireo olivaceus            Red-eyed Vireo
Vireo philadelphicus       Philadelphia Vireo
Zonotrichia albicollis     White-throated Sparrow

Species                    Bluebell   Bohm   Sweet William

Catharus fuscescens          0.00     0.00       0.15
Catharus ustulatus           0.60     1.53       0.08
Contopus virens              2.10     1.36       2.39
Dumetella carolinensis       0.00     0.00       0.23
Empidonax alnorum            0.00     0.00       0.15
Empidonax flaviventris       0.30     0.00       0.46
Empidonax virescens          2.10     6.79       2.16
Hylocichla mustelina         1.95     4.07       2.08
Icterus galbula              0.00     0.34       0.08
Myiarchus crinitus           2.40     1.19       3.47
Passerina cyanea             5.69     8.49       4.01
Pheucticus ludovicianus      0.15     0.34       0.00
Piranga olivacea             0.00     0.00       0.46
Piranga rubra                0.00     0.34       0.08
Polioptila caerulea          4.04     1.19       2.47
Sayornis phoebe              0.00     0.00       0.08
Spizella passerine           0.30     0.00       0.15
Toxostoma rufum              0.30     0.00       0.15
Troglodytes aedon            0.30     0.00       0.85
Tyrannus tyrannus            0.30     0.00       0.08
Vireo flavifrons             0.00     0.34       0.15
Vireo gilvus                 0.00     0.00       0.15
Vireo griseus                0.30     0.00       0.31
Vireo olivaceus              6.89     5.09       5.63
Vireo philadelphicus         0.00     0.34       0.31
Zonotrichia albicollis       0.15     1.02       0.00

Table 4. Estimated population densities (individuals/ha) for
resident passerines in 3 forest patches in Madison County, IL.

Species                     Common Name

Agelaius phoeniceus         Red-winged Blackbird
Baeolophus bicolor          Tufted Titmouse
Cardinalis cardinalis       Northern Cardinal
Carduelis tristis           American Goldfinch
Corvus brachyrhynchos       American Crow
Cyanocitta cristata         Blue Jay
Mimus polyglottos           Northern Mockingbird
Molothrus ater              Brown-headed Cowbird
Pipilo erythrophthalmus     Eastern Towhee
Poecile atricapilla         Black-capped Chickadee
Poecile carolinensis        Carolina Chickadee
Quiscalus quiscula          Common Grackle
Sialia sialis               Eastern Bluebird
Sitta carolinensis          White-breasted Nuthatch
Sturnus vulgaris            European Starling
Thryothorus ludovicianus    Carolina Wren
Turdus migratorius          American Robin

Species                     Bluebell    Bohm     Sweet William

Agelaius phoeniceus           0.60      0.34         0.00
Baeolophus bicolor            7.79      5.77         5.09
Cardinalis cardinalis        12.58      6.45         9.80
Carduelis tristis            11.38      4.24         4.48
Corvus brachyrhynchos         0.75      0.00         0.77
Cyanocitta cristata           1.50      0.68         1.62
Mimus polyglottos             0.00      0.00         0.31
Molothrus ater                5.09      2.89         4.63
Pipilo erythrophthalmus       5.54      1.53         3.63
Poecile atricapilla           1.05      0.00         0.00
Poecile carolinensis          5.69      2.89         7.18
Quiscalus quiscula            1.80      0.00         0.62
Sialia sialis                 0.00      0.00         0.15
Sitta carolinensis            0.75      2.21         2.24
Sturnus vulgaris              0.30      0.00         0.00
Thryothorus ludovicianus      1.20      1.70         2.86
Turdus migratorius            2.40      4.92         1.77

Table 5. Estimated population densities (individuals/ha) for
nonpasserines in 3 forest patches in Madison County, IL.

Species                 Common Name

Archilochus colubris    Ruby-throated Hummingbird
Chaetura pelagica       Chimney Swift
Coccyzus americanus     Yellow-billed Cuckoo
Colaptes auratus        Northern Flicker
Dryocopus pileatus      Pileated Woodpecker
Melanerpes carolinus    Red-bellied Woodpecker
Meleagris gallopavo     Wild Turkey
Picoides pubescens      Downy Woodpecker
Picoides villosus       Hairy Woodpecker

Species                 Bluebell    Bohm     Sweet William

Archilochus colubris      0.60      2.55         0.39
Chaetura pelagica         0.00      1.70         0.00
Coccyzus americanus       0.90      0.68         0.46
Colaptes auratus          0.45      1.36         0.15
Dryocopus pileatus        0.30      0.85         0.46
Melanerpes carolinus      1.35      2.55         2.16
Meleagris gallopavo       0.00      0.00         0.15
Picoides pubescens        3.15      3.90         2.08
Picoides villosus         0.75      2.21         0.85

Table 6. Indicator species analysis for 3 forest patches in
Madison County, IL. Tabulated indicator values are the product of
fidelity and constancy. P values are based on 10,000 random
permutations of group membership. Species with P < 0.2 are shown.
A liberal P-value of 0.2 since was used since this was an
exploratory analysis rather than an explicit test of hypotheses.
Bold values indicate the group for which the species is a
significant indicator.

Species                    Common Name

Baeolophus bicolor         Tufted Titmouse
Cardinalis cardinalis      Northern Cardinal
Carduelis tristis          American Goldfinch
Pipilo erythrophthalmus    Eastern Towhee
Poecile atricapillus       Black-capped Chickadee
Polioptila caerulea        Blue-gray Gnatcatcher
Quiscalus quiscula         Common Grackle
Archilochus colubris       Ruby-throated Hummingbird
Catharus ustulatus         Swainson's Thrush
Chaetura pelagica          Chimney Swift
Colaptes auratus           Northern Flicker
Dendroica petechia         Yellow Warbler
Dendroica virens           Black-throated Green Warbler
Empidonax virescens        Acadian Flycatcher
Hylocichla mustelina       Wood Thrush
Picoides pubescens         Downy Woodpecker
Picoides villosus          Hairy Woodpecker
Turdus migratorius         American Robin
Zonotrichia albicollis     White-throated Sparrow
Oporornis formosus         Kentucky Warbler
Poecile carolinensis       Carolina Chickadee
Thryothorus ludovicianus   Carolina Wren

                                              Sweet
Species                    Bluebell   Bohm   William     P

Baeolophus bicolor            26       14      12      0.1401
Cardinalis cardinalis         35       16      28      0.1058
Carduelis tristis             32       8        8      0.0055
Pipilo erythrophthalmus       20       3       12      0.1258
Poecile atricapillus          6        0        0      0.1181
Polioptila caerulea           19       3        9      0.1053
Quiscalus quiscula            11       0        2      0.0385
Archilochus colubris          1        17       0      0.0051
Catharus ustulatus            1        9        0      0.037
Chaetura pelagica             0        13       0      0.0027
Colaptes auratus              1        12       0      0.0213
Dendroica petechia            0        11       1      0.0149
Dendroica virens              0        9        0      0.0313
Empidonax virescens           3        41       4      0.0001
Hylocichla mustelina          4        15       5      0.124
Picoides pubescens            10       17       4      0.125
Picoides villosus             2        14       2      0.0559
Turdus migratorius            6        20       4      0.0409
Zonotrichia albicollis        0        9        0      0.0155
Oporornis formosus            0        0        6      0.1546
Poecile carolinensis          18       7       25      0.1737
Thryothorus ludovicianus      2        7       17      0.1497

Table 7. Observations of additional species encountered during
sampling period outside of 25 m plots and not included in species
richness or density estimates.

Species                     Common Name

Branta canadensis           Canada Goose
Buteo jamaicensis           Red-tailed Hawk
Cathartes aura              Turkey Vulture
Catharus guttatus           Hermit Thrush
Charadrius vociferous       Killdeer
Coccyzus erythropthalmus    Black-billed Cuckoo
Colinus virginianus         Northern Bobwhite
Dendroica tigrina           Cape May Warbler
Helmitheros vermivorum      Worm-eating Warbler
Passerina caerulea          Blue Grosbeak
Spizella pusilla            Field Sparrow
Sturnella magna             Eastern Meadowlark
Vermivora pinus             Blue-winged Warbler
Zenaida macroura            Mourning Dove

Species                     Bluebell   Bohm   Sweet William

Branta canadensis              11       4           7
Buteo jamaicensis              --       2          --
Cathartes aura                 2        1          --
Catharus guttatus              --       1           3
Charadrius vociferous          1        --         --
Coccyzus erythropthalmus       1        --          1
Colinus virginianus            3        3           5
Dendroica tigrina              1        --         --
Helmitheros vermivorum         --       --          2
Passerina caerulea             --       --         --
Spizella pusilla               11       3           8
Sturnella magna                1        --         --
Vermivora pinus                1        --         --
Zenaida macroura               3        1           2

Table 8. Observations of additional species encountered outside
of sampling period and not included in species richness or
density estimates.

Species                  Common Name

Circus cyaneus           Northern Harrier
Megaceryle alcyon        Belted Kingfisher
Strix varia              Barred Owl
Vermivora chrysoptera    Golden-winged Warbler
Vireo bellii             Bell's Vireo

Species                  Bluebell    Bohm     Sweet William

Circus cyaneus              --         1           --
Megaceryle alcyon           --         1           --
Strix varia                 --         1           --
Vermivora chrysoptera       --         1           --
Vireo bellii                --        --            1
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Publication:Transactions of the Illinois State Academy of Science
Article Type:Report
Geographic Code:1USA
Date:Jan 1, 2010
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