Point Blue Conservation Science

About: Point Blue Conservation Science is a nonprofit organization based out in Petaluma, California, United States. It is known for research contribution in the topics: Population & Foraging. The organization has 151 authors who have published 330 publications receiving 11929 citations. The organization is also known as: Point Reyes Bird Observatory.

Intra-tropical migration and wintering areas of Fork-tailed Flycatchers (Tyrannus savana) breeding in São Paulo, Brazil

Abstract: Fork-tailed Flycatchers ( Tyrannus s. savana ) breed from central to southern South America from September to January, migrating to northern South America to spend the non-breeding season. However, little is known of the migratory routes, rate, and timing of migration of those that breed in Brazil. In 2013, we attached light-level geolocators to breeding Fork-tailed Flycatchers breeding in Sao Paulo State. Data for six male flycatchers recaptured in 2014 indicates that they exhibited two fall migration strategies. Some individuals migrated northwest to the wintering grounds (primarily Colombia, Venezuela and northern Brazil), while others first spent several weeks in southwestern Brazil before going to the wintering grounds. Mean fall migration rate was 69 km/day (±13.7) during 59 (±13.2) days. Some flycatchers moved during winter, using more than one winter area. Flycatchers initiated spring migration in July and migrated southeast to the breeding grounds at a mean rate of 129 km/day (±19.0) during 27 (±2.8) days. A detailed understanding of the annual cycle of South America's migratory birds is essential to evaluating theoretical questions, such as the evolution of their life history strategies, in addition to applied questions, such as explanations for changes in population size, or their role as disease vectors.

Invasive plants decrease microbial capacity to nitrify and denitrify compared to native California grassland communities

Abstract: Exotic plant invasions are a major driver of global environmental change that can significantly alter the availability of limiting nutrients such as nitrogen (N). Beginning with European colonization of California, native grasslands were replaced almost entirely by annual exotic grasses, many of which are now so ubiquitous that they are considered part of the regional flora (“naturalized”). A new wave of invasive plants, such as Aegilops triuncialis (Barb goatgrass) and Elymus caput-medusae (Medusahead), continue to spread throughout the state today. To determine whether these new-wave invasive plants alter soil N dynamics, we measured inorganic N pools, nitrification and denitrification potentials, and possible mediating factors such as microbial biomass and soil pH in experimental grasslands comprised of A. triuncialis and E. caput-medusae. We compared these measurements with those from experimental grasslands containing: (1) native annuals and perennials and (2) naturalized exotic annuals. We found that A. triuncialis and E. caput-medusae significantly reduced ion-exchange resin estimates of nitrate (NO3 −) availability as well as nitrification and denitrification potentials compared to native communities. Active microbial biomass was also lower in invaded soils. In contrast, potential measurements of nitrification and denitrification were similar between invaded and naturalized communities. These results suggest that invasion by A. triuncialis and E. caput-medusae may significantly alter the capacity for soil microbial communities to nitrify or denitrify, and by extension alter soil N availability and rates of N transformations during invasion of remnant native-dominated sites.

A Quantitative Evaluation of the Conservation Umbrella of Spotted Owl Management Areas in the Sierra Nevada

Abstract: Whether by design or default, single species management often serves as an umbrella for species with similar habitat requirements. In recent decades the focus of National Forest management in the Sierra Nevada of California has shifted towards increasing closed canopy mature forest conditions through the protection of areas occupied by the California Spotted Owl (Strix occidentalis occidentalis). To evaluate the implications of these habitat changes and the potential umbrella resulting from a system of owl reserves on the broader avian community, we estimated occupancy of birds inside and outside of Spotted Owl Home Range Core Areas in northeastern California. We used point count data in a multi-species hierarchical Bayesian model incorporating the detection history of 81 species over a two-year time period (2005-2006). A small set of vegetation cover and topography covariates were included in the model to account for broad differences in habitat conditions, as well as a term identifying whether or not a site was within a Core Area. Seventeen species had a negative Core Area effect, seven had a positive effect, and the rest were not significant. Estimated species richness was significantly different with 23.1 species per 100 m radius circle outside Core Areas and 21.7 inside Core Areas. The majority of the species negatively associated with Core Areas are tied to early successional and other disturbance-dependent habitats. Conservation and climate vulnerability rankings were mixed. On average we found higher scores (greater risk) for the species positively associated with Core Areas, but a larger number of species with the highest scores were negatively associated with Core Areas. We discuss the implications for managing the Sierra Nevada ecosystem and illustrate the role of monitoring broader suites of species in guiding management of large complex ecosystems.