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California towhees (Pipilo crissalis) defend all-purpose, type-A territories throughout the year and are believed to remain on home ranges for successive breeding seasons. I present the first data regarding use of space by California towhees from a long-term study of a color-banded population. I examined individual site-fidelity to home ranges over 5 breeding seasons and combined this information with radiotelemetry data to assess sizes of home ranges and use of habitats. California towhees exhibited strong site-fidelity to breeding territories. All (n = 31) individuals located >10 times in a season were site-faithful across years for up to 4 years. Average size of home range was 0.83 ± 0.31 ha. Size of home range did not differ by sex, and paired birds occupied similar home ranges. All home ranges were composed of a variety of habitats, including open field, dense forest, and riparian areas. California towhees used habitat types differentially throughout the breeding season, and nested in a variety of plants. Prior to and following nesting, they were most often in open areas that provided good forage. While nesting, males and females were most often in dense vegetation. Because they defend type-A territories year-round, potentially for their entire lives, California towhees may benefit from settling on home ranges with high diversity of habitats that can meet fluctuating needs for resources. [ABSTRACT FROM AUTHOR]

We investigated factors at multiple scales that might influence nest predation risk for Spotted Towhees (Pipilo maculatus) along the Sacramento River, California, within the context of large-scale riparian habitat restoration. We used the logistic-exposure method and Akaike's information criterion (AIC) for model selection to compare predator search, predator abundance, restoration, and temporal effects hypotheses. Our candidate models represented restoration, temporal, nest activity, nest concealment, agriculture, and flood effects. Restoration sites did function as breeding habitat, with nest survival comparable to mature forest sites and some young being produced. The best-supported models contained the covariates cowbird young in host nest and calendar date. All supported models contained the covariate cowbird young, the only variable with a strong effect. In contrast to our prediction, nest survival increased with cowbird young in the nest, implicating adult cowbirds in nest predation events. Nest survival declined throughout the breeding season and increased marginally with nest concealment. We calculated the finite rate of population increase (λ), using a model that incorporated nest success estimates for parasitized and unparasitized nests, double brooding, the locally observed cowbird parasitism rate for Spotted Towhees, number of young fledged from successful parasitized and unparasitized nests, adult survival and a range of juvenile survival values, estimated as percentages of adult survival. Values of λ did not approach the replacement level of one, indicating that this population is not self-sustaining. We recommend extensive habitat restoration in the floodplain landscape, ideally in conjunction with cowbird control, to reduce nest predation and parasitism pressures. [ABSTRACT FROM AUTHOR]

Fire alters the structure and composition of shrublands and affects habitat quality for the associated avifauna. Because shrubland ecosystems have been greatly reduced from their original extent in western North America and fire is increasingly being used to manage these landscapes, a better understanding of how fire affects the associated vegetation and wildlife is imperative. We evaluated the response of Green-tailed Towhees (Pipilo chlorurus) to prescribed fire in the montane shrublands of Rocky Mountain National Park, Colorado during 2002 and 2003. Three to five years following prescribed burning, Green-tailed Towhee density and shrub cover were generally higher in unburned areas. Nests (n = 179) were located in unburned vegetation; within burned sites, all nests were in remnant patches. Green-tailed Towhee nest survival was 57% (95% Cl = 65%) across the two years of the study. More than half of the nests were in common juniper (Juniperus communis) shrubs, and nest survival was higher for nests in junipers than those in other shrub species. Daily nest survival rates were lower at the site with the highest density of towhees and declined over the breeding season. With regard to shrub cover, opposite trends were observed for nest-site selection and nest survival: nest plots had greater shrub cover than non-nest plots, but nest survival decreased with increasing shrub cover. Because shrub cover affects towhee density and nest survival in conflicting ways, fire management at Rocky Mountain National Park alters both habitat availability and suitability for Green-tailed Towhees. [ABSTRACT FROM AUTHOR]

Models of habitat selection commonly asume that higher-quality source habitats will be occupied at higher densities than sink habitats. We examined an apparent sink habitat for California Towhees (Pipilo crissalis) in which densities are greater than in nearby source habitats. We estimated territory density using spot-mapping and monitored nests of towhees in grazed and ungrazed oak-pine woodland habitat. Breeding density of California Towhees was higher in ungrazed oak-pine woodlands than in grazed areas, yet birds in the ungrazed site experienced lower reproductive success. Predation during the nestling period was primarily responsible for the lower nest success. Clutch size and the number of young fledged were also lower in the ungrazed site. Towhees selected nest sites with high foliage density and cover of live oaks (Quercus wislizenii) in the understory. Grazed sites had greater cover of live oak than ungrazed sites, and successful nests were more often built in live oak than in other plant species. This pattern could not be explained by dominant birds settling in grazed sites and excluding subdominant individuals because a large proportion of adults continued to settle in the ungrazed area. Towhees may have perceived the dense foliage of the ungrazed area as suitable due to abundant nest sites, cover, and food, resulting in an "ecological trap." The resulting high density of birds there may have contributed to density-dependent predation. Alternatively, towhees are not ideally adapted to their habitats because of their sedentary habits and site tenacity that is not affected by persistent nest loss. We stress the need to examine the reproductive success and productivity of individual species within specific habitat types. [ABSTRACT FROM AUTHOR]