Seabird Sizes / December 15, 2018 by Michael Johns

This figure depicts the relative sizes of seabirds that breed on the Farallon Islands. Larger circles mean more massive birds, smaller circles less massive. Species in the order Pelecaniformes, colored in shades of blue, are among the largest birds that breed on the island. The Ashy Storm-petrel in yellow, although a part of the order Procellariiformes which includes some of the largest seabirds like albatrosses, is small enough to fit inside the palm of your hand. The diverse order Charadriiformes in shades of red includes all of the gulls and auks, the latter of which contains all of the wing-propelled pursuit divers like puffins, murres, guillemots, and auklets. Mass information was gathered from the Sibley guide to birds. This plot was made almost entirely in R, with a few minor tweaks made in Photoshop. A full size image can be downloaded HERE.

Make It An Animation / November 18, 2018 by Michael Johns

Sometimes, an animated figure tells the story better than a static one. We have been tracking the non-breeding movement patterns of Cassin’s auklets from Southeast Farallon Island since 2015, in an effort to understand the environmental drivers of their winter dispersal. Part of the work I’m doing for my PhD is linking the movements of auklets to remotely sensed conditions relevant to their foraging ecology, in the case of this animation chlorophyll-a concentration (left) and sea surface temperature (right) from November 2017 through January 2018. Chlorophyll, the photosynthetically active molecule that gives plants, algae, and certain types of bacteria their green pigment, is used as a measure of the concentration of phytoplankton. Krill, which comprises much of the Cassin's auklet diet, graze on phytoplankton, so it’s reasonable to assume productive areas with high concentrations of chlorophyll-a likely contain greater densities of krill than areas of low chlorophyll-a. Similarly, lower sea surface temperatures are generally associated with nutrient rich cold water from depth, which help spark blooms of phytoplankton. One hypothesis, visualized with this animation, is that Cassin’s auklets are searching for colder regions of higher productivity during the winter months. The next step is to test this hypothesis with a series of competing models, to see which best explains the patterns observed in the data.

Visualizing Long-term Data / September 16, 2018 by Michael Johns

Point Blue Conservation Science has amassed an impressive long-term dataset on the breeding histories of known-age Cassin's auklets on Southeast Farallon Island. These data are visualized in the figure above. The dedication to maintaining and checking 400+ artificial nest boxes every 5-days for the past 34 years has allowed researchers to reveal some unique patterns in the life history of this small seabird. For example, Cassin's auklets are the only member of the taxonomic Alcid family to attempt two complete broods in a single breeding season, known as double brooding. In a recent study published in the journal Proceedings of the Royal Society B, my colleagues and I used these data to examine how double brooding impacts future reproductive potential and survival for birds that attempt such a behavior multiple times over the course of their lives. It turns out that so called "repeat double brooders" represent a subset of high quality individuals that can offset the short-term costs of increased reproductive effort, living well into old age and producing more offspring than birds that never double brood. Visit the publisher’s website by clicking HERE.

Winter Movements / September 2, 2018 by Michael Johns

After several years of geolocator tagging work (see image below), we finally have enough information to begin to paint a better picture of the non-breeding winter distribution of Cassin's auklets from Southeast Farallon Island. At the start of any research project, the most important first step in the analysis process is to visualize the data. The idea behind this visualization was to depict three key environmental characteristics of the auklet's winter habitat in a single plot; sea surface temperature (SST), depth, and distance from island. SST will be used as a proxy for productivity, as colder water in this region is generally associated with nutrient rich upwelling processes, depth to characterize the preferred ocean zone (shallow shelf, steep slope, or deep abyssal plain), and distance from island to explore the possible limits of their dispersal.

Glancing at this plot, you can see by October birds are fairly spread out between 45°N (dark purple colors - Northern California area) and roughly 33°N (orange colors - Southern California). They are also exposed to quite a range of SST, from 14°C up to nearly 22°C. By late January, all of the birds are relatively close to the island (small bubble size) and experiencing roughly the same SST, before spreading out again in late February, with most birds staying at around 35°N. The 2015-16 season was a particularly warm year for SST, which my explain why only birds in the northern reaches were finding water colder than 14°C. The next step in this exploratory process is to look at auklet movements during the 2016-17 and 2017-18 seasons, which were moderate to average years for SST in the eastern north Pacific. Ultimately, these and possibly additional environmental covariates will be used to model the winter habitat use of Cassin's auklets off the California Coast.

Note the geolocator tag on the left leg of this Cassin's auklet. Geolocators are devices which record ambient light levels that are later used to estimate latitude and longitude.

Tagging data courtesy of a partnership between Point Blue Conservation Science and the USFWS. Remotely sensed environmental data were downloaded from the NOAA repository https://coastwatch.pfeg.noaa.gov/erddap. This plot was created in R with the ggplot2 package.

Relative Size / May 7, 2018 by Michael Johns

Probably the most important question in the conservation work that we do, and the most popular question people have about the Farallones, is the population size of the various seabird species on the island. The answer, such as roughly 250,000 murres, 20,000 auklets, and 500 puffins, may not be fully appreciated when taken at face value. The figure above is an attempt to put these numbers into context by representing each population as a collection of boxes, where the area of each box is scaled in proportion to the other boxes. With this visualization, you can see just how abundant Common Murres are in relation to Pigeon Guillemots or Tufted Puffins. With continued monitoring and management, hopefully all of these boxes will continue to grow in size.

Data courtesy of a partnership between Point Blue Conservation Science and the USFWS. The plot is called a "Treemap", created in R with the ggplot2 and treemapify packages.