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Linking foraging decisions to residential yard bird composition

Publication date: 2016-11-30

Author(s):

  • Susannah Lerman, USDA Forest Service Northern Research Station

Abstract:

Urban bird communities have higher densities but lower diversity compared with wildlands. However, recent studies show that residential urban yards with native plantings have higher native bird diversity compared with yards with exotic vegetation. Here we tested whether landscape designs also affect bird foraging behavior. We measured the amount of resources remaining, or giving-up densities (GUD) for final foragers on artificial food patches in residential yards in Phoenix, AZ, USA. We assessed how two yard designs (mesic: lush, exotic vegetation; xeric: drought-tolerant and native vegetation) differed in foraging costs. Further, we developed a statistical model to calculate GUDs for every species visiting the patch. Birds foraging in mesic yards depleted patches to a lower level (i.e. had lower GUDs) than birds foraging in xeric yards. After accounting for bird densities, the lower GUDs in mesic yards appeared largely driven by invasive and synanthropic species. Furthermore, yard design affected individual species behavioral responses. Species visiting trays in both yard designs had lower GUDs in mesic yards. Differences in the missed opportunity (alternative resources more abundant in xeric yards) and the digestive cost (moist conditions in mesic yards) both contributed to our results while predation costs did not. Enhancing the GUD method with our statistical model provided insights into how individual species and bird densities influenced the GUD. If the described differences we found in foraging behavior are indicative of differences in habitat quality, then this would lend additional support for native landscapes to help reverse the loss of urban bird diversity.

Keywords:


Temporal Coverage:

2010-02-13 to 2010-05-03

Geographic Coverage:

Geographic Description: CAP LTER study area
Bounding Coordinates:
Longitude:-113.34 to -111.59
Latitude:34.01 to 32.91

Contact:

Data Manager, Julie Ann Wrigley Global Institute of Sustainability, Arizona State University, 
PO Box 875402,Tempe
 caplter.data@asu.edu

Methods used in producing this dataset: Show


Data Files (2) :

Tabular: 639_species_density_c8396bf588fb003f7a20fba1a145731b.csv

Description: study site (residential yards) details, and bird foraging patterns of study seed-trays

Column Description Type Units
Location Name of homeowner where experiment took place
string
Yard Type Landscape design of yard: Mesic = turf and exotic plants, Xeric = crushed gravel and drought tolerant vegetation
string
Enumeration:
  • Mesic: yard characterized by turf and exotic plants
  • Xeric: yard characterized by crushed gravel and drought tolerant vegetation
Treatment Placement of the seed tray: Bush = next to plants, Open = 3 meters away from plants
string
Enumeration:
  • Bush: seed tray positioned next to plants
  • Open: seed tray positioned 3 meters away from plants
Species AOU bird code
string
SpDensity Total number of individuals for the species observed foraging on seed tray
float number
GUD (g) GUD = Giving-up densities, the amount of seed remaining after foraging experiment ends in the seed tray
float gram
ExpModel_GUDlog_0=20 Predicted GUD based on an exponential model of the GUD data
float gram
SeedConsumed Total number of seeds consumed per tray
float number
total Pecks Total number of pecks for the species
float number
Peck % Percent of pecks by the species for the seed tray
float dimensionless
GUD pecks Total number of pecks for the seed tray when the species stopped pecking on seed tray
float number
Order Order the species stopped pecking on seed tray
float number
Total Tray Pecks Total number of pecks for the seed tray (all species, all visits)
float number
Minimum Individuals Total number of individual birds observed foraging on seed tray
float number
Total Species Total number of species observed foraging on seed tray
float number

Tabular: 639_predation_3fc65738044a7753a56425db96214a09.csv

Description: study site (residential yards) details, and bird predation patterns

Column Description Type Units
Location Name of homeowner where experiment took place
string
TYPE Landscape design of yard: Mesic = turf and exotic plants, Xeric = crushed gravel and drought tolerant vegetation
string
Enumeration:
  • Mesic: yard characterized by turf and exotic plants
  • Xeric: yard characterized by crushed gravel and drought tolerant vegetation
S - Date Start date
date Format: YYYY-MM-DD
E - Date End date
date Format: YYYY-MM-DD
S - Time Start time
date Format: HH:MM:SS
E - Time End time
date Format: HH:MM:SS
Experiment Placement of the seed tray: Bush = next to plants, Open = 3 meters away from plants
string
Enumeration:
  • Bush: seed tray positioned next to plants
  • Open: seed tray positioned 3 meters away from plants
T-min Minimum temperature
float celsius
T-max Maximum temperature
float celsius
GUD GUD = Giving-up densities, the amount of seed remaining after foraging experiment ends in the seed tray
float gram
Notes? Notes for the experiment
string
Last Species Last species observed foraging on the seed tray
string
2nd Last Species Second to last species observed foraging on the seed tray
string
3rd Last Species Third to last species observed foraging on the seed tray
string
4th Last Species Fourth to last species observed foraging on the seed tray
string
5th Last Species Fifth to last species observed foraging on the seed tray
string
6th Last Species Sixth to last species observed foraging on the seed tray
string
Total Species Total number of species observed foraging on seed tray
float number
Minimum Individuals Total number of individual birds observed foraging on seed tray
float number
Species configuration Total number of individuals for each species observed foraging on seed tray
string

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