sprawl and fragmentation: how much development deters native bird species? mary ann cunningham, jake...

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