data viz

Visualizing Long-term Data 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 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. 

Listers by Michael Johns

The Farallon Islands are uniquely situated for people interested in the hobby of finding and identifying birds, otherwise known as "birding". The cluster of jagged rocks are located just far enough offshore to provide a stable platform for spotting rare pelagic species like the Cook's petrel, and close enough to the mainland to catch vagrant song birds and other terrestrial species lost in the fog at sea. Over the course of 50 years of research out on the Farallones, some biologists and staff have been keeping a detailed list of all of the different bird species they've encountered while out on the island, a record known as "The Faralist". This figure is a graphical interpretation of that list, modified from R code for a similar graphic depicting the number of days spent on island by various people over the years. Collectively, a total of 429 different species have been seen from the Farallones; not bad for a small collection of guano-covered rocks with only 3 trees.

Download a high resolution file of this figure HERE.  

Landscape of a Year by Michael Johns

Animals tend to be fairly predictable in their reproductive timing and migration patterns. The figure above depicts a series of density curves, with peaks and troughs corresponding to the average timing of key biological events for a select number of marine species that are monitored on or from Southeast Farallon Island.

Pinnipeds, a taxonomic group that includes seals and sea lions, are found hauled out on the island year round, with peak pupping events occurring in the summer. Northern fur seals, which have made an astounding recovery on the Farallones following the days of the Russian Fur Trade, remain at sea for several months of the year and are only seen in force from summer to late fall. Whales are also visible from the island year round. Gray whale numbers peak in January as they migrate south to their breeding grounds off Baja California Mexico, and again in March during a northward migration back to their feeding grounds in Alaska. Humpback and blue whales are most abundant in the productive summer months, where they are seen gorging themselves on krill and schooling fish. For seabirds, breeding occurs only in the summer months, with the exception of the ashy storm-petrel which extends chick rearing well into October. Three distinct peaks represent the timing of egg laying, hatching, and chick fledging. 

The study of seasonal life-history patterns is called phenology, and it can tell us a lot about the stability of a system. As I mentioned, animals tend to be fairly predictable in their phenology. Individuals cue in on environment and biological signals, so shifts in the timing of reproduction or migration can indicate changes in environmental condition, food availability, or the health of a population. For species found on the Farallones, the major cause for concern in the face of a warming ocean is the availability of key prey items, namely krill, which sustain the rich biodiversity in this region. A mismatch between the timing of krill and the timing of reproduction for seabirds can lead to major declines in breeding success, and subsequent declines in population numbers. 

Data courtesy of a partnership between Point Blue Conservation Science and the USFWS. The plot was created in R with the ggplot2 and ggridges packages. 

Relative Size 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. 

50 Years of Bands by Michael Johns

It's been 50 years since scientists from Point Blue Conservation Science (then Point Reyes Birds Observatory) began a continuous monitoring effort on SE Farallon Island. Some of this work includes banding certain species of seabirds to learn more about their movement patterns, survival and mortality rates, population status, and individual breeding behavior and success; all important information guiding management decisions and tracking the potential effects of climate change. Point Blue has amassed an impressive sample of banded birds since work first started in 1967, totaling nearly 125,000 individuals as of 2016. The graphic below illustrates the total bands put out by year and cumulatively since 1967 for 8 target species.