Sprawl and Fragmentation:
How Much Development Deters Native Bird Species? Mary Ann Cunningham, Jake Hoffman
Vassar College
1940 1970 2004Built Tax Parcels
Dutchess CountyNY
Questions:
1. Are native, woodland bird species inhibited by urbanization on the urban fringe?
2. Which gradients of urbanization are most important in predicting these species?(road density, tree cover, built density, proximate conditions)
3. Can easily-calculated measures, e.g. focal statistics, support multiple-scale investigations? (as alternative to digitizing/interpreting landcover data)
Study area approx 14 x 6 km (85 km2)
Study Area
Poughkeepsie, NY
Representative of the peri-urban region
Methods:Point counts (5 min, 100 m radius)Distributed at 500 m intervals on E-W transects
Explanatory variables:Proximate habitat: % cover (grass, shrub, trees, pavement); feeder (p/a), tree hights Calculated %road area (moving window/focal statistics over study area)
Euclidean distance to nearest road (distance function)
Average built parcel size ( built density)
Interpolated surface from tax parcel centroids using parcel size as value (natural neighbor interpolation)
Digitized Tree cover %trees at 4 scales
Digitized Tree cover %trees at 4 scales
300 m 600 m 900 m 1200 m
Results:
Bird counts:84 observations34 species, using P/A measures, most < 10 occurrences
Results:
Bird counts:84 observations34 species, using P/A measures, most < 10 occurrences
ANOVA:
indicates difference in variable value between presence and absence observations
Significant Results (small sample sizes make results provisional!)
(using Chi2 or backwards anova)
Species N Temp Feeder Grass Trees Shrubs Pavemt PctRoads (300 m)
PctRoads (600 m)
PctRoads (900 m)
Distance to roads
Parcel size
American Crow 56 .021+ .008- .038- .015+ .0006+ .0016+
Black-capped Chickadee 44
White-breasted Nuthatch 20 .016- .003+
European Starling 14 .07 <.0001+
Tufted Titmouse 14 .086- .048-
Northern Cardinal 13 .005+ .013+ .102+ .105+ .033-
Blue Jay 12 .022+
Dark-eyed Junco 12 .038- .010+ .005+ .011+ .072- .041-
Downy Woodpecker 12 .012+ .015-
Mourning Dove 10 .003+ .020+ .105+ .086- .098-
White-throated Sparrow 9 .031+ .086+
Herring Gull 8 .002- .038- .003+
Red-tailed Hawk 8 .080- .086- .086-
House sparrow 6
Rock Dove (Pigeon) 6 .023- .053+ <.0001+ <.0001+ .0002+ .055-
American Goldfinch 5
Northern Mockingbird 4
Pileated Woodpecker 4 .022+ .078+
Red-bellied Woodpecker 4 .092+
Significant Results (small sample sizes make results provisional!)
(using Chi2 or backwards anova)
Species N PctTrees (300 m)
PctTrees (600 m)
PctTrees (900 m)
PctTrees(1200m)
American Crow 56 <.0001 - <.0001 - <.0001 -<.0001 -
Black-capped Chickadee 44
White-breasted Nuthatch 20
European Starling 14 .103 - .-17 - .015 - .092 -
Tufted Titmouse 14 .044+ .067+ .072+ .092+
Northern Cardinal 13
Blue Jay 12
Dark-eyed Junco 12 .041 - .037 - .076 - .053 -
Downy Woodpecker 12
Mourning Dove 10 .049 - .053 - .168 - .189 -
White-throated Sparrow 9 .090 - .189 -
Herring Gull 8 .010 - .025 - .004 - .004 -
Red-tailed Hawk 8
House sparrow 6 .052 - .039 - .022 - .009 -
Rock Dove (Pigeon) 6 .001 - .001 - .001 - .001 -
American Goldfinch 5
Northern Mockingbird 4
Pileated Woodpecker 4 .048 + .074 +
Red-bellied Woodpecker 4
Species Temp Feeder Grass Trees Shrubs Pavement PctRoads (300 m)
PctRoads (600 m)
PctRoads (900 m)
Distance to roads
Parcel size
Urban .0001- .002 - .0001+ .0003+ .0001+ .0001+ .055- .017-Suburban .069-
Species PctTrees (300 m)
PctTrees (600 m)
PctTrees (900 m)
PctTrees(1200m)
Urban <.0001 - <.0001 - <.0001 - <.0001 -Suburban
Urban vs. Suburban groups
Scale patterns
Species N PctTrees (300 m)
PctTrees (600 m)
PctTrees (900 m)
PctTrees(1200m)
American Crow 56 <.0001 - <.0001 - <.0001 -<.0001 -
Black-capped Chickadee 44
White-breasted Nuthatch 20
European Starling 14 .103 - .017 - .015 - .092 -
Tufted Titmouse 14 .044+ .067+ .072+ .092+
Northern Cardinal 13
Blue Jay 12
Dark-eyed Junco 12 .041 - .037 - .076 - .053 -
Downy Woodpecker 12
Mourning Dove 10 .049 - .053 - .168 - .189 -
White-throated Sparrow 9
Herring Gull 8 .010 - .025 - .004 - .004 -
Red-tailed Hawk 8
House sparrow 6 .052 - .039 - .022 - .009 -
Rock Dove (Pigeon) 6 .001 - .001 - .001 - .001 -
American Goldfinch 5
Northern Mockingbird 4
Pileated Woodpecker 4 .048 + .074 +
Red-bellied Woodpecker 4
Ubiquitous species
Feeder species
Woodland species
Urban species
Christmas Bird Count results
Number in 2004
Conclusions:
1. Native species, woodland species show relatively little effect on the range of urbanization gradients in the study area
Urban species, including invasives, show relatively large effects
-----------2. Percentage road area = easy to calculate, useful factor Distance = not useful in suburban contexts (gradients too small) Parcel size = easy to calculate but less useful than road area
All of these are easier to assess accurately than LULC or digitized tree cover.BUT tree cover is still generally more influential
-----------3. Despite small samples, trends were consistent over scales
Focal statistics is a useful, easy approach to multiple-scale studies