Fig 1.
Overview of experimental design.
The map identifies the location of the eight studied Cactus Wren territories within Orange County. The flow chart indicates the different data sources and sample sizes and how they are integrated in analyses. Details on each data stream and analyses procedures are provided in Methods text.
Table 1.
Outcome of Coastal Cactus Wren nesting efforts across territories monitored in 2012.
Productivity was tracked among territories in terms of the date that the first egg was laid, the total number of nesting attempts, eggs laid, fledgling success, and the timing and causes of nesting failure.
Fig 2.
Arthropod orders and suborders in (a) Coastal Cactus Wren diet samples and (b) nesting territories. Arthropod taxa are ranked by the frequency of occurrence among diet samples. The total estimated biomass is given at the territory-scale for canopy and ground arthropods. Symbols show the variation in estimated biomass among territories (color) and site (shape). Grey bars show the mean biomass (+ SE) across all territories (n = 8). Biomass estimates are drawn on a log scale.
Fig 3.
Territory- and habitat-element-specific estimates of arthropod density among habitat elements from canopy sampling (top row) and ground pitfall traps (bottom row).
Grey bars show the biomass of non-native arthropods, Isopoda and Hymenoptera. White bars show the biomass of arthropod orders included in diet samples. Points are shown for each bird nesting territory, with shape referencing the study site and each territory a different color. Arthropods were sampled from native plant species; Artemisia californica (ARCA), Erioginum. fasciculatum (ERFA), O. littoralis (OPLI), Rhus integrifolia (RHIN), Sambucus nigra (SANI), and grasses (NAGR).; non-native Brassica nigra (BRSP) and grasses (EXGR); and bare ground (BARE). Bare ground was sampled by both pitfall sampling and vacuum collecting any arthropod observed within 0.5 m of the pitfall trap, referred to as canopy sampling above for consistency with plant sampling.
Fig 4.
Mean biomass (mg ±SE) of prey orders from field-sampled arthropods across focal habitat elements in the canopy (top row) and on the ground (bottom row).
Arthropods were sampled from native plant species; Artemisia californica (ARCA), Eriogonum fasciculatum (ERFA), O. littoralis (OPLI), Rhus integrifolia (RHIN), Sambucus nigra (SANI), and grasses (NAGR).; non-native Brassica nigra (BRSP) and grasses (EXGR); and bare ground (BARE). Bare ground was sampled by both pitfall sampling and vacuum collecting any arthropod observed within 0.5 m of the pitfall trap, referred to as canopy sampling above for consistency with plant sampling.
Fig 5.
Relationships between the first egg date and territory-level estimates of prey (mg) (left column), first egg date and Hymenoptera biomass (mg) (middle column) and territory-level estimates of prey (mg) and Hymenoptera biomass (mg) (right column).
Results presented for plant canopies (top row) and on the ground (bottom row).
Fig 6.
Territory-level relationships between arthropod prey composition and first egg date in plant canopies and on the ground.
PC loadings are provided in the first row for PC axes representing variation in arthropod prey composition. Variation in composition is considered separately for canopy (columns 1 & 2) and ground (columns 3 & 4) arthropods. Trend lines indicate significant (P < = 0.05) correlation between axes. PC1 and PC2 for canopy composition explain 50% and 29% of variation and for ground composition explain 58% and 29% of variation (see S4 Fig in S1 Appendix).