Increasing the Accuracy of Productivity and Survival Estimates in Assessing Landbird Population Status

Abstract

The conservation of species with declining populations requires information on population demography and identification of factors that limit population growth. For landbird species, an understanding of large-scale population declines often requires assessment of local population processes, including the production of offspring, the survival of those offspring, and adult survival. Population growth has been modeled for several species of landbirds to date, and these studies have provided important information on relationships between population status and population-limiting factors. Several recent studies have illuminated field methods and analytical techniques that can aid in increasing the accuracy of productivity and survival estimates for population models. We reviewed these methods and recommend their implementation, including quantification of the season-long productivity of individuals, collection of empirical data on juvenile survival during the postfledging and overwintering periods, and incorporation of adult breeding dispersal into annual adult survival estimates. Such methods will allow for more accurate assessment of population status and provide a better understanding of the factors on which to focus our conservation efforts.Resumen: La conservación de especies con poblaciones en declinación requiere de información sobre su demografía y la identificación de factores que limitan el crecimiento poblacional. Para especies de aves terrestres, el entendimiento de declinaciones poblacionales a gran escala a menudo requiere de la evaluación de procesos poblacionales locales, incluyendo la producción de descendencia, la supervivencia de esa progenie y la supervivencia de adultos. A la fecha, se ha modelado el crecimiento poblacional de varias especies de aves terrestres, y esos estudios han proporcionado información importante de las relaciones entre estatus de la población y factores que limitan a la población. Varios estudios recientes han clarificado métodos de campo y técnicas analíticas que pueden ayudar a incrementar la precisión de estimaciones de productividad y supervivencia en modelos poblacionales. Revisamos estos métodos y recomendamos su aplicación, incluyendo la cuantificación de la productividad estacional de individuos, la recolecta de datos empíricos de supervivencia de juveniles durante los períodos de postemplumaje e invierno y la incorporación de dispersión reproductiva de adultos en estimaciones de supervivencia anual de adultos. Tales métodos permitirán una evaluación más precisa del estatus de la población y proporcionarán un mejor entendimiento de los factores a enfocar en nuestros esfuerzos de conservación.Palabras Clave: ave terrestre, demografía, estimación de Mayfield,éxito de anidación, modelos poblacionales, productividad, supervivencia de adultos, supervivencia de juveniles

Seasonal productivity in a population of migratory songbirds: why nest data are not enough

“…Based on our results, and those of other recent studies (Anders and Marshall 2005), fledgling songbird survival is generally lower and more variable than the values included in population models. We agree with Anders and Marshall (2005) that in the absence of fledgling survival data, population models should include lower and more variable values for first-year survival than in previous modeling efforts. However, our results demonstrate that fledgling survival can be relatively high in years (and in areas) that nest productivity is relatively low, and that population growth can be more sensitive to fledgling survival than to nest productivity.…”

The demography of Yellow WagtailsMotacilla flavaon abandoned fields in northern European Russia

“…Demographic parameters responsible for changes in population size are fecundity, survival probability, and dispersal probability (Cilimburg et al 2002, Anders & Marshall 2005. Because breeding dispersal is difficult to document, permanent emigration and mortality are usually not distinguished in estimates of passerine survival (Cilimburg et al 2002, Gilroy et al 2012.…”

Conservation biology for suites of species: Demographic modeling for Pacific island kingfishers

“…To determine whether survival in juveniles, helpers, and dominants should be separated by class, sex, both, or neither in the matrix model, Cormack-Jolly-Seber estimation methods were applied to color band resight data (described above; Pollock et al, 1990;Lebreton et al, 1992). We estimated both apparent survival and the probability of resight because individuals may have been present on study areas but missed when resighting color-bands (Anders and Marshall, 2005). We constructed biologically reasonable survival models with covariates for sex and life-stage, and combined parameter estimates (Table 1).…”