Tucson’s Birds: Why Scale Matters Rachel McCaffrey

In developed areas, factors controlled by humans are important to determining whether native bird species persist Vegetation –Volume –Composition –Diversity Land-use –Types –Arrangement –Intensity Bird Occurrence Abundance Diversity Composition

Volunteer-based bird survey program Abundances and distribution Annual, citywide count ~ 1,000 sites, 1/km 2 Quarterly, “Park” count ~ 200 sites at 30 locations

Annual Survey Sites

Park Monitoring Sites

Research Focus Birds and habitat features in residential developments: an issue of scale

What we know: Urban areas have less diverse groups of birds ↑ in non-native species Some types of development support more native birds

Scale is important! urban areas = heterogeneity and disturbance (Hostetler 1999)

Local vs. landscape features Individual yardsSurrounding area Species Dependent!

Why is this important? which which scale = species and scale-specific management guidelines homeowners neighborhoods planners

Study Design Randomly selected 300 sites

Bird surveys 5-minute point count, 40 m radius Each site surveyed 4 times, March 15 – June species

Habitat features - Local 0.5-ha circular plot (40 m radius) –Represents typical residential lot –On-site measurements Features measured based on known habitat requirements of species

Habitat features - Local Number of: –cholla cacti (> 1m) –saguaro cacti (> 2m) –mesquite and palo verde trees (> 3m) –native thorn trees (> 2m) –large “roost” trees (> 5m) –palm trees (> 5m) –homes Presence of: –desert mistletoe –wash Percent of vegetation that is native

Habitat features - Landscape 50-ha circular plot (399 m radius) –Represents typical neighborhood/development –Used digitalized aerial photographs & GIS Features measured based on habitat requirements and management potential

number of washes percent of area in open space percent of area covered by lawn presence of natural area > 5 ha Habitat features - Landscape

Regression analyses: Which features are most important for each species at each scale? Variance decomposition: Was a species most influenced by features at the local or landscape scale? Data Analysis

Results Average of 5.5 species/site 21.6% of sites 87.8% of sites

Results – Local Scale number of thorn trees number of cholla number of mesquite and palo verde trees overall percent native vegetation number of homes

Results – Landscape Scale number of washes (4) percent of area in open space (6) percent of area covered by lawn (3)

Results - Scale Species most influenced by local scale features: Cactus wren Curve-billed thrasher Phainopepla

Cactus wren Number of cholla Percent of sites with cactus wrens

Results - Scale Species most influenced by landscape scale features : Ash-throated flycatcher Lesser goldfinch

Ash-throated flycatcher Number of washes Percent of sites with Ash-throated Flycatchers

Results - Scale Species most influenced by shared associations: Gambel’s quail Gila woodpecker Northern cardinal Pyrrhuloxia Verdin

Pyrrhuloxia Influenced most by shared associations across scales…… Local: % native vegetation Landscape: % open, % lawn (-) E.J. Peiker

The Influence of Scale Importance of habitat features varied by species and scale Cross-scale interactions Need scale-specific management strategies!

Local scale implications Individual homeowners can have an impact! plant thorn trees, cholla, native trees

Landscape scale implications Neighborhood groups and developers of master-planned communities can take broader actions: ban/limit lawns promote native landscaping incorporate open space restore riparian areas

A multi-scale approach Homeowner plants thorn trees Development incorporates open space Regional planning efforts to maintain riparian networks

In Conclusion….. The persistence of many native birds in urban areas will depend on: Identifying key habitat features Understanding the relevant scales Targeting management efforts