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Sprawl and Fragmentation: How Much Development Deters Native Bird Species? Mary Ann Cunningham, Jake Hoffman Vassar C PowerPoint Presentation
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Sprawl and Fragmentation: How Much Development Deters Native Bird Species? Mary Ann Cunningham, Jake Hoffman Vassar College Built Tax Parcels Dutchess County NY 1940 1970 2004 Questions: 1. Are native, woodland bird species inhibited by urbanization on the urban fringe?

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Sprawl and Fragmentation: How Much Development Deters Native Bird Species?Mary Ann Cunningham, Jake Hoffman Vassar College

Built Tax Parcels

Dutchess County

NY

1940 1970 2004

slide2

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)

slide3

Study Area

Poughkeepsie, NY

Study area approx 14 x 6 km

(85 km2)

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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)

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Average built parcel size ( built density)

Interpolated surface from tax parcel centroids using parcel size as value

(natural neighbor interpolation)

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Results:

Bird counts:

84 observations

34 species,

using P/A measures, most < 10 occurrences

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Results:

Bird counts:

84 observations

34 species,

using P/A measures,

most < 10 occurrences

ANOVA:

indicates difference in

variable value between

presence and absence

observations

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Significant Results

(small sample sizes make results provisional!)

(using Chi2 or backwards anova)

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Significant Results

(small sample sizes make results provisional!)

(using Chi2 or backwards anova)

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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

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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

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3. Despite small samples, trends were consistent over scales

Focal statistics is a useful, easy approach to multiple-scale studies