Figure 1.
Study site locations in southwestern Wisconsin.
Squares and circles indicate sites used for tree row removals and controls, respectively. Shaded polygons depict developed areas, labeled by town name. Lines represent major highways.
Table 1.
Mean male density (males/ha) and standard errors (in parentheses) for obligate grassland birds in tree row edge and grassland interior habitats at the control and treatment sites.
Table 2.
Mean apparent nest density (number/ha) and standard errors (in parentheses) for obligate grassland birds in tree row edge and grassland interior habitats on the control and removal sites.
Figure 2.
Annual maps of nest dispersion.
Nests of the 3 focal species relative to the focal tree row, edge, and interior habitat at a tree row removal site in southwest Wisconsin. More nests occurred in the tree row edge area following the removal of woody vegetation. Dots refer to nest locations by species, with: blue for bobolink, yellow for Eastern meadowlark, and red for Henslow’s sparrow.
Table 3.
The probabilities (Daily Survival Rates) for nests fledging ≥1 young, listed by species pooled at the whole field level by treatment.
Figure 3.
Probability of fledging ≥1 young by species and treatment.
Because control and tree row removal sites were paired, the areas and time-periods are comparable. Due to the low number of nests near tree rows (egdes), data were pooled for the control sites and pre-treatment years.
Table 4.
AIC results for nest success on control and tree row removal sites.
Table 5.
Coefficients for the minimum AICc models for bobolink and Eastern meadowlark from Table 4.
Figure 4.
Nest depredation by predator group and year.
Proportions for the (A) control and (B) tree row removal sites.
Table 6.
Mean percent activity (± SE) for species recorded as common potential nest predators (occurrence/station/day x 100) in tree row edge and grassland interior habitats on the control and tree row removal sites.
Table 7.
Summary of the relative impacts on birds of tree row removal.