Table 1.
Research questions, predictions from hypotheses, and statistical approaches to testing each.
Fig 1.
Classification of satellite images (top row) into suburban vegetation classes (bottom row) at original breeding site during year of occupancy (Territory A, Year 1), original breeding site during year it was abandoned (Territory A, Year 2), and new breeding site during year of occupancy (Territory B, Year 2).
In this example of a Pacific wren, the breeding male moved 647m from Territory A to Territory B in association with clearing of a portion of his former territory for construction of a new subdivision.
Fig 2.
Breeding dispersal by songbirds in an urbanizing environment.
The frequency of movements by distance category is separated by guild in this stacked bar figure (gray portion of bars is 47 distances moved by avoiders and black portion is 457 distances moved by adapters and exploiters).
Table 2.
Territory size, site fidelity, apparent death of partner, and mate fidelity of songbirds spot-mapped in forested landscapes surrounding Seattle, WA, USA, from 2003–2010.
Assessment of site fidelity was done within each landscape and summed here for an overall proportion because territory size varied among species and among landscapes (S1 Table). When a banded bird remated with a new partner and it’s mate from the prior year was not detected in the study area, we concluded the prior mate was apparently dead. Species abbreviated as follows, Bewick’s wren: BEWR; dark-eyed junco: DEJU; song sparrow: SOSP; spotted towhee: SPTO; Swainson’s thrush: SWTH; Pacific wren: PAWR.
Fig 3.
Average (+1SE) breeding dispersal distance by guilds in each of three landscapes.
Sample size above error bars.
Fig 4.
Breeding dispersal distance of adapters / exploiters (A) and avoiders (B) in response to vegetation changes associated with construction of new subdivisions.
The most influential vegetation variable for each guild is used as the x-axis. For adapters / exploiters this was the total amount of forest within 100m of the new territory center. For avoiders it was the difference in total forest within 100m of the new territory center minus the old territory center (positive values indicate increases in forest cover at the territory each bird dispersed to. Shading of points indicates mate fidelity (A) or annual productivity (B), which were found to be important to each guild. Least-squares regression line ± 95% CI are fitted to data.