Riparian vegetation along the Sacramento RiverCalifornia's largest river-has been almost entirely lost, and several wildlife species have been extirpated or have declined as a result. Large-scale restoration efforts are focusing on revegetating the land with native plants. To evaluate restoration success, we conducted surveys of landbirds on revegetated and remnant riparian plots from 1993 to 2003. Our objectives were to estimate population trends of landbirds, compare abundance patterns over time between revegetated and remnant riparian forests, and evaluate abundance in relation to restoration age. Of the 20 species examined, 11 were increasing, 1 was decreasing (Lazuli Bunting [Passerina amoena]), and 8 showed no trend. The negative trend for Lazuli Bunting is consistent with information on poor reproductive success and with Breeding Bird Survey results. There was no apparent guild association common to species with increasing trends. Nine species were increasing on revegetated and remnant plots, four were increasing on revegetated plots only, three were increasing on remnant plots only, the Lazuli Bunting was decreasing on both, and three species were stable on both. Although many species were increasing at a faster rate on revegetated plots, their abundance did not reach that of the remnant plots. For revegetated plots, ''year since planting'' was a strong predictor of abundance trends for 13 species: positive for 12, negative for 1. Our study shows that restoration activities along the Sacramento River are successfully providing habitat for a diverse community of landbirds and that results from bird monitoring provide a meaningful way to evaluate restoration success.

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Ornithologists commonly estimate nest survival using the Mayfield method, which produces relatively unbiased estimates provided that key assumptions are met. However, this method cannot statistically model nest failure in relation to quantitative variables, nor can it consider the joint effects of two or more independent variables. We demonstrate the use of an alternative method, survival time analysis. Survival time analysis can incorporate nests that are found at different points in the nesting cycle and nests whose ultimate outcome is unknown. The method allows one to examine variation in nest mortality during the course of the nesting period. To demonstrate this method we analyze data on Loggerhead Shrike (Lanius ludovicianus) nests, collected as part of a 3-year monitoring program of shrubsteppe habitat in north-central Oregon. We evaluate nesting success with respect to laying date, nest height, and annual variation in failure rate. We demonstrate three types of analyses: Kaplan-Meier estimation (a nonparametric method), Cox proportional hazards model (a semiparametric method), and Weibull parametric regression. Using these maximum-likelihood methods one can carry out likelihood-ratio tests and Akaike's Information Criterion model selection. The best predictive model included the effects of date and year. Nest failure rate changed during the nesting cycle and was heterogeneous among nests, thus violating assumptions of the Mayfield method. We discuss drawbacks to the use of logistic regression (another Mayfield alternative) to analyze nest success. Estimates of the age of a nesting attempt upon discovery are required for survival time analysis; we encourage ornithologists to collect such information.Uso del Análisis de Tiempo de Sobreviviencia para Analizar el Éxito de Nidificación: Un Ejemplo Utilizando Lanius ludovicianusResumen. Los ornitólogos generalmente utilizan el método de Mayfield para estimar la sobrevivencia de los nidos, un método que produce estimaciones relativamente poco sesgadas siempre y cuando se cumplan sus suposiciones claves. Sin embargo, este método no es capaz de modelar estadísticamente los fracasos de nidificación en relación con variables cuantitativas, ni tampoco puede considerar el efecto conjunto de dos o más variables independientes. Aquí, demostramos el uso de un método alternativo, el análisis de tiempo de sobrevivencia, el cual puede incorporar nidos que son encontrados en diferentes tiempos durante el ciclo de nidificación y también nidos cuyo resultado final es desconocido. El método permite examinar la variación en la mortalidad de nidos durante el transcurso del período de nidificación. Con el fin de demostrar este método, analizamos datos de nidos de Lanius ludovicianus colectados como parte de un programa de monitoreo del hábitat de estepa arbustiva durante un período de 3 años en Oregon nor-central. Evaluamos el éxito de nidificación con respecto a la fecha de puesta, altura del nido y variación anual en la tasa de fracaso. Demostramos tres tipos de análisis: estimación de Kaplan-Meier (un método no paramétrico), modelos de riesgo proporcional de Cox (un método semi paramétrico) y regresión paramétrica de Weibull. Utilizando estos métodos de máxima verosimilitud uno puede seleccionar modelos realizando pruebas de cocientes de verosimilitudes y utilizando el criterio de información de Akaike. El modelo con mayor capacidad predicativa incluyó los efectos de la fecha y el año. La tasa de fracaso de nidos varió durante el ciclo de nidificación y fue heterogénea entre nidos violando así, las suposiciones del método de Mayfield. Discutimos las desventajas del uso de regresiones logísticas (otra alternativa al método de Mayfield) para el análisis del éxito de los nidos. Para el análisis de tiempo de sobreviviencia se requiere la estimación de la edad de un intento de nidificación en el momento de ser descubierto, por lo que sugerimos a los ornitólogos colectar dicha información.

Rapid growth in off‐highway vehicle (OHV) use in North America leads to concerns about potential impacts on wildlife populations. We studied the relationship between distance to active OHV trail and songbird nesting success and abundance in northeastern California, USA, from 2002 to 2004. We found evidence of greater nest desertion and abandonment and reduced predation on shrub nests <100 m from OHV trails than at nests >100 m from OHV trails. Two of 18 species studied were less abundant at sites on trails than at sites 250 m from trails, and no species were more abundant on trails. Management of OHV trail development should consider possible negative impacts on nesting success and abundance of breeding birds.