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A City-wide Breeding Bird Survey for Washington, D.C.
John Hadidian, U.S. National Biological Survey, Center for Urban Ecology, 4598 MacArthur Blvd., Washington, D.C. 20007
John Sauer, U.S. National Biological Survey, Patuxent Environmental Science Center, Laurel, MD 20708
Christopher Swarth, Audubon Naturalist Society, 8940 Jones Mill Road, Chevy Chase, MD 20815
Paul Handly, U.S. National Park Service, National Capital Region, 1100 Ohio Drive SW, Washington D.C. 20037
Sam Droege, U.S. National Biological Survey, 1849 C St. NW, Washington, D.C. 20240
Carolyn Williams, Audubon Naturalist Society, 8940 Jones Mill Road, Chevy Chase, MD 20815
Jane Huff, Audubon Naturalist Society, 8940 Jones Mill Road, Chevy Chase, MD 20815
George Didden, Audubon Naturalist Society, 8940 Jones Mill Road, Chevy Chase, MD 20815
Urban birds populations have recreational, conservation and scientific values that are not always fully appreciated. Urban parks and refuges offer stop-over points for migrants and nesting habitats for many species. Bird feeding is an activity enjoyed by millions of back-yard enthusiasts that generates a multi-million dollar annual investment (Shaw & Mangun 1984). Bird watching has captured the interest of a growing community of individuals who derive pleasure from observing and identifying birds in the field. While each of these factors alone could be significant, combined they place a premium on the study of urban bird populations.
The project reported on here was initiated by the Audubon Naturalist Society of Maryland as a way to promote the educational, recreational and scientific value of conducting a citywide survey of breeding bird species. Its objective was to survey the bird species occurring throughout Washington, D.C. during the 1993 breeding season. This was accomplished through a coordinated planning effort and partnership between the Audubon Naturalist Society, the National Park Service, and the National Biological Survey, engaging the participation of more than 100 highly skilled volunteers. A method for rapidly assessing the status of bird populations over a large area was developed and incorporated into a Geographic Information System (GIS) to allow a multidimensional analysis of species presence and abundance across a variety of urban land use areas. This approach produced a prototype monitoring program for urban bird populations that will be repeated in the future. The resultant information will be used to characterize the ability of urban and suburban areas to sustain different species or guilds of birds, and to promote the experiential and educational value of bird study.
The study area included all of metropolitan Washington, D.C. area, an area comprising about 64 mi2 (Figure 1). Sixteen land use classes, used by the District's Office of Planning (Anon 1992), were aggregated into seven from information that was digitized and entered into a GIS (Table 1).
Survey points were established by imposing a 500 meter grid created as a GIS layer over a base map derived from U.S. Census Bureau TIGER files and digital data from the U.S. Geological Survey (1:24000) that portrayed park boundaries, streams and trails (Figure 1). A total of 717 survey points fell within the boundaries of Washington, but those located in bodies of water were not surveyed, as well as a few others where safety or access issues prevented counts being taken. A few points were not sampled because of logistical or scheduling problems. Although data were collected for both 1993 and 1994, we only used 1994 information from 38 points that were not sampled in 1993, to augment total coverage of points. In all, a total of 617 points were actually sampled.
The census period began annually on May 23 and ended on June 30. Five minute point counts were used to sample bird populations (Ralph 1993). Ninety-five field maps were created using a PC
Figure 1. Map of Washington, D.C. showing the city's political boundaries with a superimposed 500 m sampling grid, as used in the citywide breeding bird survey conducted in 1993.
based GIS (Atlas*GIS, Strategic Mapping, Inc., 4030 Moorpark Avenue, Suite 250, San Jose, CA. 95117). Experienced observers were recruited locally and assigned between one and ten map areas. A total of 87 individuals participated in the 1993 counts and 53 in 1994. Surveys were conducted between sunrise and 9:30 a.m. on mornings when wind did not hinder observer's ability to hear birds and no steady rain was falling. Data taken at each point included the species heard or seen, the time, weather conditions and number of birds for each species observed. Although actual numbers of individuals of each species were recorded, the potential for high interobserver variability in such counts (Bart and Schoultz 1984) precluded analysis for this report.
Data for each sampling point were entered onto a PC database manager and converted into the file format compatible with the PC GIS. Species presence data was subsequently joined with coordinate information derived from the original 500 meter sampling grid. By associating coordinates with each record, we were able to compare the bird census data with geospatial information on land use and other attributes.
For each species, we calculated the proportion of points on which it occurred in each land use category. We then tested the null hypothesis that these proportions did not differ among the categories using 2 (Sauer and Williams 1989). Rejection of the null hypothesis indicates that the species is counted at a smaller proportion of points in at least some land use categories. If the species were not seen on any points for a land use category, that category was not used in the statistical comparison.
The observed number of species is a biased estimate of the actual number of species because species are often missed during the counts. To minimize the effects of this bias, we estimated species richness using methods derived from capture-recapture procedures (Pollock et al. 1990), using sightings of birds as an analogue for captures. To estimate species richness with these procedures, species are used rather than individuals as the items that are "captured", and count locations are treated as the capture occasions. Burnham and Overton (1979) developed an estimation procedure that allows for heterogeneity in capture probabilities among species and uses a jackknifing procedure to estimate total species richness. We used a computer program developed by J. D. Nichols and J. E. Hines (Patuxent Environmental Science Center, Laurel, M.D., unpublished) to implement this procedure. The program provides estimates of species richness and an estimated standard error from input data on number of points on which each species was counted.
We estimated species richness both overall (for all points) and for points in each land use category for several groups of species. To compare species richness among groups, we again used a 2 test (Sauer and Williams 1989). Species richness estimates may be inefficient when only small numbers of species are present (Magurran 1988), and we did not use them to adjust the counts in the analysis of data from individual count locations or for groups with small numbers of species. For all tests we set an alpha level of 0.10, because we wanted to examine inclusive groups of species for each analysis procedure. We recognized that there were many other chances for false inclusions to occur and that the few false inclusions introduced by the higher alpha level would be offset by the more inclusive search desired in this pilot study.
Although total species richness is of interest, many land managers are particularly concerned about subsets of species. For example, birds that migrate from neotropical areas are currently experiencing population declines (Robbins et al. 1989), making their conservation of particular import to many, including urban planners. Because North American birds have well-known habitat affinities (Ehrlich et al. 1988), they can be grouped into breeding habitat associations, or guilds. We recognized five of these, following Peterjohn and Sauer (1993), including (1) Wetland & Open Water, (2) Successional-Scrub, (3) Woodland, (4) Urban, and (5) a Neotropical Migrant group, composed of species that winter primarily in the Neotropics (Table 2).
A total of 91 species were observed at 617 sample points (Table 3). The average number of species at a given point was 6.9 (SD=3.8, range= 0-20). The observed number of species and total numbers of birds varied greatly among the land use classes (Table 3), as was easily discernable by mapping the species through the GIS. For example, the mapped distribution of Wood Thrush clearly shows that this species has a strong affinity for larger park land areas (Figure 2). Species distributions can be summed and averaged using GIS 'smoothing' algorithms to more broadly characterize how birds are distributed throughout the urban landscape (Figure 3).
Sixty-two of the 91 species (68%) either were associated only with or exhibited a strong affinity for a single land use category (Table 4). Eleven species reached their maximum frequency of occurrence in low density residential areas, three in residential areas dominated by row and multi-family dwellings, and one in the high density (apartment complex) residential areas. Thirty-six species reached maximum frequency of occurrence on park lands, seven on the industrial-airport land use category, and four on public and institutional lands. No species reached a maximum frequency of occurrence in points
Figure 2. Distribution of the Wood Thrush throughout Washington D.C. during the survey period of 1993.
Figure 3. Total species richness for Washington, D.C. during the 1993 survey period.
falling within commercial land use areas. Twenty-nine species did not show any significant association with a particular land use area. However, even the majority of these species were not found in some land use categories, and only four species (Eastern Kingbird, Blue Jay, Fish Crow, and Common Grackle) were actually found across all land use classes.
First, four species, Great Black-backed Gulls, Mourning Warbler, Blackpoll Warbler, and Purple Finch do not breed in the district, and represent incidental or accidental occurrences. //Other species do not breed, e.g. gb heron. Need complete list of nonbreeders and appropriate wording to describe these four -- incidental? Twenty-three species were seen only at a single point, and only 12 species were seen at >100 points. Of the 37 Neotropical migrant species seen in the study, 26 were either only found, or reached their maximum frequency of occurrence in parks. Many of the Neotropical migrants are also woodland habitat species, and 23 of the 29 woodland nesting species also reached their maximum frequency of occurrence in parks. Some species (e.g. woodcock) are known to occur in DC but were not recorded....
Total estimated species richness for Washington, D.C. was 115 (SE + 8). Species richness differed significantly (P < 0.01) among land use categories, being highest in park lands and lowest on commercial lands (Table 4). Species richness among guilds followed predictable patterns (Table 5), with generally similar numbers of urban guild members in all land use categories, but woodland, scrub, and wetland species showing distinct differences in their affinity for different land use categories. Woodland and scrub nesting species had highest richness in park land and low density residential categories. The commercial land use category had the lowest species richness for all guilds of birds.
Although urban bird populations have been fairly well studied, citywide surveys appear to be rare, with Guth's (1979) systematic sampling within metropolitan Chicago and a citywide breeding bird atlas for London (Montier 1977, Cousins 1983) the only examples we were able to locate of efforts akin to that reported here. Studies of urban bird communities and their habitat affinities clearly demonstrate a complex relationship between species richness, abundance (number of birds) and habitat structure (Emlen 1974, Vale and Vale 1976, Campbell and Dagg 1976, Lancaster and Rees 1979, Jones 1981, DeGraaf et al. 1991). Urban areas appear to produce highly heterogenous habitat opportunities for avian species, representing a challenge for researchers interested in elucidating the relationship between species diversity and increasing urbanization (Bratten 1972; Walcott 1974) as well as the effects of habitat fragmentation and isolation on species presence and richness (Goldstein et al. 1981, Soule et al. 1988).
Washington D.C. appears to provide both diverse and good quality habitat for birds, a finding that we attribute largely to the fact that low and moderate density residential areas and parks make up more than 70% of the metropolitan area. The 115 species estimated in our overall diversity estimate agrees closely with totals known from the recent past (Hampe & Kolb 1947, McAtee 1951, Hodge 1976), and is almost as high as in the surrounding counties, even with their larger size. Far from being conservation wastelands, urban areas may play an important role in addressing regional and even national concerns for conserving biological diversity.
This study employed a Geographic Information System to (1) create a sampling design, (2) produce field maps identifying sampling locations, (3) collate and store collected information, (4) analyze data and (5) to share information. The resultant mapping of species richness is unbiased since all areas under consideration are sampled within a uniform grid system. We believe that such procedures will allow city planners and conservation groups to quickly visualize and identify those areas of the city where avian species richness is greatest. This technique may be most effectively applied in conservation planning in the suburban and outlying (exurban) zones where development and land use decisions still impact relatively large areas. In assessing development potential, as well as impacts, maps of avian diversity could provide hard planning assessment data much the same way that water and air quality assessments and school districting currently do. Without such a tool, planners would be left only with demographic studies of citizen's needs for wildlife and recreation areas, which tend to view parks as merely greenspace divorced from the land's inherent conservation values.
This project and similar programs provide a relatively inexpensive means of documenting the pattern of avian biodiversity within an urban landscape. Although not designed with this intent, this project effectively was a test and verification of the effectiveness of partnerships through which federal and private sector involvement led to a the coordination of complex activities to aid in conservation efforts. With periodic repetitions programs such as this can provide a mechanism to assess regional changes in the distribution and abundance of bird species. Such projects need not be limited to urban areas, but could be implemented across suburban and rural landscapes at county and perhaps even state levels. Through thematic data integrated into GIS systems, conservation groups and planners could identify and protect areas of greatest avian biodiversity, as well as those that support rare, endangered or sensitive species of special conservation interest.
Regardless of the role of urban and suburban environments may play in conserving avian species diversity, the educational and experiential value of projects such as that described here are important, and are likely to become increasingly significant as the process of urbanization continues to influence our evolving landscape.
More than 100 volunteers, far too many to list individually, participated in the bird survey. We acknowledge their effort by stating simply that none of this would have been possible without them. Funding and support for this project were provided by the Audubon Naturalist Society and the Washington Biologist's Field Club. For their ideas and encouragement we would like to thank Tony White, Eugene Morton, John Bjerke, Bob Ford, Dave Johnston and members of the New Columbia Audubon Society. We thank Stephanie Shepherd for her tireless contribution to the production of field maps. Access to many of the areas sampled would not have been possible unless permitted, and we thank the many individuals who arranged for this, including B. Rankin, B. Sullivan, M. Baldy, Dr. G.R. Zannia, D. Moran, L. Manley, M. Washington, R. Buckingham, Dr. P. Vogt, N. Churkis, J.W. Hawkins, L. Dobbs, W. Sterling, K. Momberger, L. Horn, L. McKenzie, K. Roberts, D. Roddy, S. Syphax, and D. Crookston.
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Table 1. Land use classes employed in a citywide bird survey, Washington, D.C., 1993.
Low density housing (single family detached & semi-detached)
Moderate density housing (row houses and duplexes)
Multiple-unit housing (mid and high-rise apartments)
Low-high density shopping and service areas
Public and Institutional
Land and facilities occupied by the Federal and District government and institutions such as universities
District and Federal parks, recreation centers, and open space
Industrial land, warehousing and wholesaling areas; includes National Airport (291 ha.)
Table 2. Guild assignments, following Peterjohn and Sauer (1993) for 91 species observed at the start of the breeding season in Washington, D.C. Species that are not confirmed as breeding in the metropolitan area are italicized; Neotropical Migrants that do not appear in other guilds are indicated in bold.
American Black Duck, Wood Duck, Great Blue Heron, Green Heron, Canada Goose, Great Egret, Snowy Egret, Red-winged Blackbird, Black-crowned Night-heron, Mallard, Bald Eagle, Ring-billed Gull, Belted Kingfisher, Osprey, Double-crested Cormorant.
Mourning Warbler, House Wren, Gray Catbird, Northern Cardinal, Carolina Wren, Yellow Warbler, Prairie Warbler, Blue Grosbeak, Rufous-sided Towhee, Field Sparrow, American Goldfinch, Song Sparrow, Brown Thrasher, Common Yellowthroat, Indigo Bunting.
Black-billed Cuckoo, Carolina Chickadee, Blackpoll Warbler, Purple Finch, Yellow-billed cuckoo, Red-bellied Woodpecker, Downy Woodpecker, Pileated Woodpecker, Eastern Wood-pewee, Acadian Flycatcher, Tufted Titmouse, Blue-gray Gnatcatcher, Veery, Wood thrush, Warbling Vireo, Red-eyed Vireo, Northern Parula, Yellow-throated Warbler, Pine Warbler, Black & White Warbler, American Redstart, Louisiana Waterthrush, Kentucky Warbler, Ruby-throated Hummingbird, Hairy Woodpecker, Great crested Flycatcher, White-breasted Nuthatch, Ovenbird, Scarlet Tanager.
American Robin, Mourning Dove, Purple Martin, House Finch, Chimney Swift, European Starling, House Sparrow, Rock Dove, Northern Mockingbird, Blue Jay, Common Grackle, Chipping Sparrow.
Black-billed Cuckoo, Purple Martin, House Wren, Gray Catbird, Mourning Warbler, Chimney Swift, Blackpoll Warbler, Yellow-billed Cuckoo, Eastern Wood-pewee, Acadian Flycatcher, Barn Swallow, Blue-gray Gnatcatcher, Veery, Wood Thrush, Warbling Vireo, Red-eyed Vireo, Northern parula, Yellow Warbler, Yellow-throated Warbler, Black & White Warbler, American Redstart, Louisiana Waterthrush, Kentucky Warbler, Blue Grosbeak, Common Nighthawk, Ruby-throated Hummingbird, Great Crested Flycatcher, Eastern Kingbird, Northern Rough-winged Swallow, Ovenbird, Common Yellowthroat, Scarlet Tanager, Indigo Bunting, Chipping Sparrow, Orchard Oriole, Baltimore Oriole.
Killdeer, Red-breasted Merganser, Great black-backed Gull, Yellow-shafted Flicker, American crow, Eastern Bluebird, Fish Crow, Eastern Phoebe, Eastern Meadowlark, Cedar Waxwing, Tree Swallow.
Table 3. Numbers of species and individuals birds found within each land use class, as defined in Table 1.
Total # Points
Total # species
Total # birds
Residential-low density (REL)
Residential-high density (REH)
Park Land (PAR)
Table 4. Species information from a citywide breeding bird census, Washington, D.C., 1993. For each species we present the number of count locations (points) on which the species was recorded, the proportion of points in each land use type on which the species was recorded, and the Chi-square test, degrees of freedom, and P value for the test of the null hypothesis that the species occurred with equal frequency in each land use type. Land use classifications are defined in Table 1. The superscript a indicates a P value of < 0.005.
Species Points REL REM REH COM FED PAR IND Chi-sq DF P
House Finch 308 0.66 0.55 0.38 0.59 0.48 0.32 0.43 44.50 6 a
American Robin 270 0.61 0.48 0.14 0.25 0.48 0.30 0.38 52.89 6 a
Northern Cardinal 201 0.49 0.25 0.19 0.03 0.22 0.39 0.16 100.11 6 a
Mourning Dove 182 0.43 0.24 0.29 0.13 0.34 0.22 0.32 25.37 6 a
Gray Catbird 162 0.43 0.18 0.14 0.09 0.18 0.26 0.32 35.70 6 a
House Wren 84 0.38 0.04 0.05 . 0.09 0.09 0.08 58.35 5 a
Carolina Chickadee 78 0.20 0.04 0.05 . 0.10 0.20 0.03 38.94 5 a
Great Black-backed Gull 3 0.02 . . . . . .
Black-billed Cuckoo 1 0.01 . . . . . .
Purple Martin 1 0.01 . . . . . .
Mourning Warbler 1 0.01 . . . . . .
European Starling 543 0.87 0.96 0.90 0.91 0.93 0.68 0.89 52.46 6 a
House Sparrow 450 0.86 0.93 0.81 0.88 0.72 0.46 0.51 135.85 6 a
Chimney Swift 364 0.58 0.76 0.71 0.69 0.58 0.40 0.51 51.40 6 a
Species Points REL REM REH COM FED PAR IND Chi-sq DF P
Rock Dove 314 0.37 0.66 0.86 0.81 0.48 0.34 0.59 88.52 6 a
Northern Mockingbird 297 0.64 0.48 0.33 0.28 0.66 0.33 0.27 62.55 6 a
Brown-headed Cowbird 36 0.07 0.01 . . 0.09 0.09 0.05 22.34 4 a
Blackpoll Warbler 1 . . . . 0.01 . .
Purple Finch 1 . . . . 0.01 . .
American Crow 389 0.67 0.52 0.24 0.25 0.66 0.73 0.51 57.90 6 a
Carolina Wren 95 0.14 0.07 . . 0.10 0.32 0.05 40.91 4 a
Tufted Titmouse 86 0.21 0.03 0.05 . 0.09 0.26 . 53.07 4 a
Red-bellied Woodpecker 55 0.12 0.02 0.05 . 0.03 0.19 . 38.36 4 a
Yellow-shafted Flicker 47 0.11 0.02 . . 0.03 0.13 0.11 20.49 4 a
Downy Woodpecker 42 0.10 . . . 0.02 0.15 . 19.39 2 a
American Goldfinch 40 0.04 0.02 0.10 0.06 0.08 0.11 0.03 12.28 6 0.06
Red-eyed Vireo 39 0.03 . . . 0.01 0.20 . 33.38 2 a
Barn Swallow 38 0.01 . . 0.06 0.09 0.12 0.05 25.76 4 a
Wood Thrush 31 0.02 . . . . 0.16 0.03 20.25 2 a
Rufous-sided Towhee 28 . 0.02 0.05 . 0.01 0.13 . 18.02 3 a
Red-winged Blackbird 22 . 0.01 0.05 . . 0.08 0.08 13.46 3 a
Eastern Wood-pewee 22 0.03 . . . 0.02 0.09 . 7.60 2 0.02
Acadian Flycatcher 20 0.01 . . . . 0.11 . 12.59 1 a
Blue-gray Gnatcatcher 17 . . . . 0.01 0.09 . 10.92 1 a
Pileated Woodpecker 14 0.02 . . . . 0.06 . 2.84 1 0.09
Species Points REL REM REH COM FED PAR IND Chi-sq DF P
Park Land (cont.)
Veery 10 0.01 . . . 0.01 0.05 . 5.04 2 0.08
Yellow-billed Cuckoo 6 . . . . . 0.04 .
Northern Parula 4 . . . . . 0.02 .
Wood Duck 3 . . . . . 0.02 .
Kentucky Warbler 3 . . . . . 0.02 .
Yellow Warbler 2 . . . . . 0.01 .
Yellow-throated Warbler 2 . . . . . 0.01 .
American Redstart 2 . . . . . 0.01 .
Great Egret 1 . . . . . 0.01 .
Snowy Egret 1 . . . . . 0.01 .
American Black Duck 1 . . . . . 0.01 .
Red-tailed Hawk 1 . . . . . 0.01 .
Eastern Bluebird 1 . . . . . 0.01 .
Warbling Vireo 1 . . . . . 0.01 .
Pine Warbler 1 . . . . . 0.01 .
Prairie Warbler 1 . . . . . 0.01 .
Black-&-white Warbler 1 . . . . . 0.01 .
Louisiana Waterthrush 1 . . . . . 0.01 .
Blue Grosbeak 1 . . . . . 0.01 .
Field Sparrow 1 . . . . . 0.01 .
Species Points REL REM REH COM FED PAR IND Chi-sq DF P
Song Sparrow 191 0.46 0.20 0.19 0.16 0.30 0.23 0.49 36.39 6 a
Mallard 40 . . . 0.03 0.02 0.13 0.14 15.14 3 a
Great Blue Heron 35 0.01 0.01 0.05 . 0.02 0.11 0.16 24.66 5 a
Ring-billed Gull 35 . 0.02 . . 0.04 0.06 0.14 9.05 3 0.03
Black-crowned Night-heron 16 0.01 . 0.05 . 0.01 0.05 0.08 7.80 4 0.10
Killdeer 15 . 0.01 . . 0.01 0.05 0.08 8.05 3 0.05
Bald Eagle 1 . . . . . . 0.03
Species with no land class preference
Common Grackle 93 0.11 0.12 0.10 0.09 0.16 0.19 0.14 5.57 6 0.47
Blue Jay 65 0.12 0.11 0.05 0.06 0.12 0.10 0.05 4.34 6 0.63
Eastern Kingbird 29 0.03 0.02 0.05 0.06 0.02 0.07 0.05 7.43 6 0.28
Fish Crow 27 0.07 0.02 0.10 0.06 0.03 0.02 0.05 5.35 6 0.50
White-breasted Nuthatch 19 0.04 . . . 0.02 0.07 . 3.68 2 0.16
Canada Goose 17 . 0.02 . 0.06 . 0.05 0.05 3.86 3 0.28
Double-crested Cormorant 16 . . 0.05 0.03 0.01 0.03 . 1.61 3 0.66
Indigo Bunting 13 0.01 0.01 0.05 . 0.01 0.05 . 7.00 4 0.14
Osprey 10 . . . . 0.02 0.03 . 0.11 1 0.74
Eastern Phoebe 10 0.01 0.01 . . . 0.04 0.03 3.15 3 0.37
Great Crested Flycatcher 10 0.02 . . . . 0.04 . 0.96 1 0.33
Common Yellowthroat 9 0.01 0.02 . . 0.02 0.02 . 1.25 3 0.74
American Kestrel 8 . 0.02 . . 0.03 0.02 . 0.72 2 0.70
Hairy Woodpecker 8 0.01 0.01 . . . 0.04 . 3.39 2 0.18
North. Rough-winged Swallow 8 . . . . 0.02 0.03 . 0.11 1 0.74
Species Points REL REM REH COM FED PAR IND Chi-sq DF P
Species with no land class preference (cont.)
Tree Swallow 7 . . . 0.03 0.02 0.01 . 0.67 2 0.72
Scarlet Tanager 7 0.01 . . 0.03 . 0.02 0.03 2.07 3 0.56
Baltimore Oriole 7 0.03 . . . . 0.01 . 1.10 1 0.29
Brown Thrasher 6 . 0.01 0.05 . 0.01 0.02 . 1.21 3 0.75
Orchard Oriole 5 . 0.01 . . . 0.02 . 0.61 1 0.44 Belted Kingfisher 5 . . . . . 0.01 0.05 1.64 1 0.20
Ovenbird 5 0.01 . . . . 0.02 . 1.40 1 0.24
Cedar Waxwing 4 0.01 . . . . 0.01 . 0.05 1 0.83
Chipping Sparrow 3 . . . . 0.02 0.01 . 0.98 1 0.32
Green Heron 3 . . . . . 0.01 0.03 0.30 1 0.58
Ruby-thr. Hummingbird 3 0.01 0.01 . . . . . 0.29 1 0.59
Red-breasted Merganser 2 0.01 . . . . 0.01 . 0.02 1 0.88
Common Nighthawk 2 . . . . 0.01 0.01 . 0.18 1 0.67
Eastern Meadowlark 2 . . . . 0.01 0.01 . 0.18 1 0.67
Table 5. Estimated species richness for all species of birds and for species grouped by breeding habitat affinities. Estimates and standard errors are presented for the 7 land use categories and overall. A * indicates that the richness estimate is the observed number of species.
Species Land Use Category
Group REL REM REH COM FED PAR IND ALL
Wetland 10 + 6 6 + 2 20 + 9 5 + 2 8 + 2 18 + 3 11 + 2 39 + 11
Scrub 21 + 8 12 + 2 12 + 3 5 + 1 13 + 3 17 + 3 7 + 1 19 + 3
Woodland 22 + 3 7 + 2 15 + 8 1 * 16 + 3 29 + 3 15 + 8 36 + 4
Urban 12 + 1 10* 11 * 10 * 11 * 12 + 1 10 * 13 + 1
Neotropical 31 + 6 11 + 3 18 + 7 6 + 1 21 + 3 39 + 4 9 + 2 46 + 4
All 62 + 5 48 + 5 41 + 5 28 + 3 45 + 4 100 + 6 43 + 4 115 + 8
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