Farallon Islands
I’ve been back from the birds of Southeast Farallon Island for a little over a month now, and I’m just getting around to digging through some of the photos from this season. This was my 6th year on the island, and every year I seem to take a diminishing number of shots. Still, the following series sums up the season pretty well.
There are approximately 500 wooden boxes (shown with a rock on top in the photo) scattered around on Southeast Farallon Island that are used as nesting habitat by Cassin’s auklets, the small seabird I’m holding in the photo. These boxes have been checked every year since 1982, where pairs of auklets using each box can be identified by a uniquely numbered metal band placed on the right leg. Some of the auklets that recruit into these boxes were banded as chicks, allowing us to track age-specific patterns of behavior, reproduction, and mortality. The bird in my hand is the oldest known-age individual currently breeding in the followed nest boxes, a female based on bill depth measurements with the band # 131319997. She received this band as a fledgling when I was still in high school back in 2001, first started breeding at age 3, and has produced 16 offspring with 3 different mates so far in her long life. We discovered her incubating a fresh new egg this year in box 212 with a new mate. At age 19, she is nearing the end of her life, and time will tell whether she manages to survive this winter to breed again next year.
This figure shows all of the known-age birds breeding in the boxed population this year. Dark grey squares at the top show the hatch year of each bird (band #’s along the x-axis), gaps are years where they were not detected, and colors show the type of breeding attempt numbered by how many chicks were fledged each year. Cassin’s auklets lay a single egg per clutch (blue squares), will relay if the initial attempt fails (yellow), and occasionally double brood (lay another egg) after they fledge their first chick (pink). Auklets can recruit as early as age 3 and live to be up to 23 years old. Most birds don’t live into old age, but a few like 131319997 surpass all expectations. Click HERE for a full resolution image.
I’ve had the great opportunity to work with an incredibly detailed long-term dataset of known-age Cassin’s auklets from the Farallones, but I think it’s important to put into perspective how much effort is required to collect these types of data. Above is a reimagined figure depicting the tenure of the many devoted people involved in maintaining a continuous time series dataset from 1967 when the field station was first established until the present. Thanks to these committed folks, we now have a unique tool for tackling a range of demographic, evolutionary, ecological, and management questions for several seabird and marine mammal species. This summer will be my 6th season on the island, which is a small drop in the bucket compared to some current and past Farallon personnel. Apologies if your names are slightly misrepresented or some of the years are missing, I still need to finish my degree after all. Full resolution figure HERE.
Sometimes a net works best when catching fish. In this case, seabird interns on Southeast Farallon Island are extracting a rhinoceros auklet from a mist net, in order to identify and measure fish the bird is bringing back to its chick. Seabirds sample the marine environment for us, and provide insights into the types of fish available around the island and within the Gulf of the Farallones National Marine Sanctuary. This particular auklet was carrying a bill load of 2 northern anchovy, a common prey item for this location.
Every season on Southeast Farallon Island has its share of surprises. From the residency of a northern gannet in 2012, to the invasion of hundreds of fork-tailed storm-petrels in 2017. This year it’s a family group of ancient murrelets, a species of wing-propelled diving seabirds that breeds well north of the Farallones.
Seabirds generally seek out remote predator-free islands as a refuge to lay eggs and rear chicks. This strategy ties individuals to their respective breeding colonies, limiting the maximum distance parents can travel to search for provisions for their chicks. Possibly as a means to overcome this limitation, ancient murrelets have adopted a different strategy. Rather than bringing food back to their chicks, they bring their chicks out to the food. A mere 1-3 days after hatching, persistent calls from devoted parents compel their chicks (up to 2 in a clutch) to take a plunge into the cold North Pacific ocean and paddle out to sea. These chicks, nothing more than buoyant balls of down with legs, follow their parents into the productive waters of the Pacific, slowly growing off a diet of zooplankton until they are big enough to fly and forage on their own.
What makes this sighting of a family group unique and exciting for the Farallones, is the fact that ancient murrelets predominately breed hundreds of kilometers away on the Aleutian Islands and throughout Southeast Alaska. A sighting of a chick off the island, which was likely no more than 25 days old, means it must have hatched somewhere relatively nearby - a noteworthy observation considering Washington State is the furthest south they’ve ever been confirmed to breed.
