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.

Trends in the Breeding Population of Adélie Penguins in the Ross Sea, 1981–2012: A Coincidence of Climate and Resource Extraction Effects

Abstract: Measurements of the size of Adelie penguin (Pygoscelis adeliae) colonies of the southern Ross Sea are among the longest biologic time series in the Antarctic. We present an assessment of recent annual variation and trends in abundance and growth rates of these colonies, adding to the published record not updated for more than two decades. High angle oblique aerial photographic surveys of colonies were acquired and penguins counted for the breeding seasons 1981–2012. In the last four years the numbers of Adelie penguins in the Ross and Beaufort Island colonies (southern Ross Sea metapopulation) reached their highest levels since aerial counts began in 1981. Results indicated that 855,625 pairs of Adelie penguins established breeding territories in the western Ross Sea, with just over a quarter (28%) of those in the southern portion, constituting a semi-isolated metapopulation (three colonies on Ross Island, one on nearby Beaufort Island). The southern population had a negative per capita growth rate of −0.019 during 1981–2000, followed by a positive per capita growth rate of 0.067 for 2001–2012. Colony growth rates for this metapopulation showed striking synchrony through time, indicating that large-scale factors influenced their annual growth. In contrast to the increased colony sizes in the southern population, the patterns of change among colonies of the northern Ross Sea were difficult to characterize. Trends were similar to southern colonies until the mid-1990s, after which the signal was lost owing to significantly reduced frequency of surveys. Both climate factors and recovery of whale populations likely played roles in the trends among southern colonies until 2000, after which depletion of another trophic competitor, the Antarctic toothfish (Dissostichus mawsoni), may explain the sharp increasing trend evident since then.

Light-level geolocator analyses: A user's guide.

Abstract: Light‐level geolocator tags use ambient light recordings to estimate the whereabouts of an individual over the time it carried the device. Over the past decade, these tags have emerged as an important tool and have been used extensively for tracking animal migrations, most commonly small birds. Analysing geolocator data can be daunting to new and experienced scientists alike. Over the past decades, several methods with fundamental differences in the analytical approach have been developed to cope with the various caveats and the often complicated data. Here, we explain the concepts behind the analyses of geolocator data and provide a practical guide for the common steps encompassing most analyses – annotation of twilights, calibration, estimating and refining locations, and extraction of movement patterns – describing good practices and common pitfalls for each step. We discuss criteria for deciding whether or not geolocators can answer proposed research questions, provide guidance in choosing an appropriate analysis method and introduce key features of the newest open‐source analysis tools. We provide advice for how to interpret and report results, highlighting parameters that should be reported in publications and included in data archiving. Finally, we introduce a comprehensive supplementary online manual that applies the concepts to several datasets, demonstrates the use of open‐source analysis tools with step‐by‐step instructions and code and details our recommendations for interpreting, reporting and archiving.

Trophic structure in open waters of the marginal ice zone in the Scotia-Weddell confluence region during spring (1983)

Abstract: The structure of the food web was investigated in open waters adjacent to the marginal ice zone in the southern Scotia Sea in spring 1983 Diets were defined for dominant zooplankton, micronekton, and flying seabird species and then aggregated by cluster analysis into feeding groups Most zooplankton were omnivorous, feeding on phytoplankton, protozoans, and in some cases, small metazoans (copepods) Only two species were found to be exclusively herbivorous:Calanoides acutus andRhincalanus gigas Micronekton were carnivores with copepods being the dominant prey in all their diets The midwater fishElectrona antarctica was the dominant food item in seven of the nine seabird species examined Cephalopods, midwater decapod shrimps and carrion were also important in the diets of a few seabird species Comparison (cluster analysis) of diets in spring with other seasons (winter, fall) indicated that over half the species examined (18 of 31) had similar diets in all seasons tested The significant intraspecific shifts in diet that did occur were attributable to regional, seasonal, and interannual effects A scheme is presented that describes the major energetic pathways through the open water ecosystem from phytoplankton to apex predators At the base are phytoplankton and protozoans which are the principal food resource for the biomass copepods and krill Krill and the biomass copepods are the principal forage of the midwater fishElectrona antarctica which, in turn, is the central diet component of flying seabirds as well as important food for the Antarctic fur seal and cephalopods Krill are a major diet element for the fur seal and cephalopods, and the principal food of the minke whale