Burrowing Owls on the Farallones??!

Yes, it’s true! There are burrowing owls on Southeast Farallon Island (aka, SEFI), and no, they are not an introduced species. Many people will be surprised to learn that these petite (10 inches tall and 1/3 pound) owls are here, because they are terrestrial owls, typically associated with expanses of flat grassland, open fields or lots, and medium-sized fossorial (burrowing) mammals such as ground squirrels or prairie dogs. SEFI is mostly rocky, devoid of burrowing mammals other than the introduced Siberian house mouse, is surrounded by ocean and nearly 30 miles from any expanse of land - hardly typical habitat for the burrowing owl. And yet they are here! The U.S. Fish and Wildlife Service and PRBO Conservation Science biologists have been monitoring the burrowing owls on the island for the last few years, and this year, they have brought on a graduate student to continue the owl monitoring and conduct a more in-depth look into the ecology of the owl. This student is Sara Lee Chandler, who is currently pursuing her Master of Science degree at San Jose State University.

The burrowing owl that occurs on SEFI is the western burrowing owl (Athene cunicularia hypugaea), a subspecies that ranges from Canada, through the Midwestern States of the U.S. and into Mexico. In California, the burrowing owl is a Species of Special Concern, and it is an endangered species in Canada. The burrowing owl population has long been in decline throughout its range - including within California - and many burrowing owl advocates within California are pressing for a more comprehensive conservation strategy and effort to protect the species from further decline.

A small number of burrowing owls make a seasonal appearance, arriving on SEFI from somewhere on the mainland in late September and sometimes overwintering as late as May. The burrowing owl does not breed on the island, but returns to the mainland to breed. One of the goals of monitoring the owls is to keep track of how long they stay on the island and where they are roosting. Sara conducts daily roost surveys of the accessible portions of the island (the seal crew conducts some of these surveys when she’s on break), scanning the nooks and crannies of the granite cliffs and slopes for an owl perched at its roost entrance, and keeping a keen eye on the ground to find pellets that have been deposited in the night. Many of the owls have been previously banded at SEFI and wear leg bands that uniquely identify them, which helps to keep track of which owl is at a particular roost.

The majority of the owls seem to prefer to roost in the innumerable rock crevices and fissures worn into the face of the island. Many of these crevices are used by breeding seabirds - such as Pigeon guillemot and Cassin’s auklet - in the summer. Sometimes burrows dug by Cassin’s auklets provide suitable habitat for the burrowing owl on the marine terrace. Sara collects the owl pellets at the roosts, which are regurgitated leftovers from an owl’s meal, and will analyze their contents to compare the composition of the owls’ winter and spring season diets. In general, however, it is known that owls are an opportunistic eater, feasting on the introduced house mice, but also preying upon songbirds, small seabirds (such as the ashy storm-petrel), beetles, and other terrestrial invertebrates on the island.

The burrowing owls, while relatively few in number, are a unique part of the ecology on SEFI. It is our hope that ecological studies of the burrowing owl on SEFI will contribute toward the knowledgebase of this charismatic animal.

Welcome to the winter season

It has been just over a week since the seasonal switchover and the winter team is settling in. We were brought to the island by a couple of wonderful Farallon patrol volunteers - Warren Sanky and Alan Weaver - who made our voyage safe and comfortable in a 40 foot power boat. During the past week the new crew has been training, becoming acquainted with the elephant seals, and getting used to an overabundant diet due to an overflowing pantry. The transition has been mediated by Russ Bradley, who is here for two weeks to show us the ropes and to entertain us in the meanwhile with many stories and the history of PRBO research on Southeast Farallon Island. He will unfortunately be leaving us on the next boat, which will be bringing the third intern to join the team, Jamie Neill.

A few introductions to the team currently on SEFI are in order:

- Ryan Berger, Winter Biologist
This is Ryan's first season as the Farallon Winter Biologist. He has a background in animal behavior with a focus on marine mammals. Before joining PRBO, he worked with manatees for the Florida Fish and Wildlife Conservation Commission. He enjoys a healthy challenge, and attempts to tag and identify Rusty have not proven disappointing.

Ryan and Rusty

-Colleen Siudzinski, Winter Intern
Colleen has been working with wildlife in the Northwestern Hawaiian Islands for the past three years. She has extensive experience working with the endangered Hawaiian monk seal. She is quite comfortable with being marooned on a small remote island, but is looking forward to an adventure in a new environment.

Colleen and MC Hammer

-Jane Khudyakov, Winter Intern
Jane studied developmental biology as a graduate student and is currently a postdoc working with microbial communities. She has been working with pinnipeds at The Marine Mammal Center during the past year. She has finally broken out of the lab for a unique field experience and is enjoying this introduction to macro-ecology.

Jane in the elephant seal blind

-Sara Chandler, Owl Biologist
Sara is a graduate student at San Jose State University who is studying the winter ecology of burrowing owls. She has long been a fan of the burrowing owl, and other raptors and songbirds too. Sara has a background in wildlife biology, environmental consulting, and vegetation monitoring. She feels very lucky to be on the island
studying one of her favorite birds.

Sara searches the cliffs for owls

The elephant seal season is underway, and the bulls are starting to show up and stake out some territory. We have identified several bulls that were here last year, including the cantankerous favorite and one of last year's alphas, Rusty, as well as others such as Bedlam Boy and MC Hammer. These bulls will soon be battling for the prime territories to gain access to their harem of females. We've been working on identifying the bulls by reading their flipper tags as well as looking out for the arrival of pregnant cows, which should start happening in the next few weeks. Once the cows settle in, they will be giving birth to pups and nursing them continuously for about 3 weeks without leaving their pup, even to feed. After the pup gains a tremendous amount of weight and is weaned, the alpha males will mate with all of the females in their territory.

Rusty

So far, we've had only three potential pregnant cows, and no sign of elephant seal pups yet. In order to be able to easily identify the potential breeders of the season, we have been working on stamping numbers on the arriving cows and bulls using hair dye. This has been a new experience for everyone on the winter team. "Crusty" Rusty especially has been quite suspicious of our attempts to read his tags and give his coat
a brand new stamp. We've been having some problems getting the "Born Blonde" hair dye to show up well on the brunette seals that we have already stamped, so we are going to try out a different dye setup which will hopefully make the numbers stand out so that we can identify the main role-players quickly from a distance.

Bedlam Boy moves up the terrace toward the house

Hind flipper tag

In between the elephant seal monitoring, our week has been consumed by extensive training for all aspects of our work on the island this season. We've practiced the routine for both the East and North boat landings, learned how to record weather conditions throughout the day, studied the names for different locations on the
island, and have been slowly becoming acquainted with the abundant bird life of the Farallones. We’re getting up to speed in terms of entering the abundant demographic data into the PRBO databases. We've also cleaned out the house and organized all of our food, fuel, and other supplies – out with the old, in with the new, for a new season.

Once we are fully settled and trained, a regular day for the elephant seal crew would go like this: a Western gull count at dawn, followed by breakfast and elephant seal monitoring. Twice a week we count all of the elephant seals present at accessible locations on the island. Once a week all of the pinnipeds are counted from the lighthouse. Twice a month, the California arboreal salamander population on SEFI is thoroughly monitored. After lunch, we go up to the elephant seal blind which hovers on a rock above Sand Flat and read elephant seal tags and note the new cow and bull arrivals. The day wraps up with a dusk gull count, data entry, and a consistently delicious dinner. After dinner, we record our findings for the day in the Farallon journal, which will eventually be bound and retained for permanent record. The workday of the burrowing owl biologist is quite different from that of the elephant seal crew, and deserves a blog post all of its own.

Farallon Superstitions – Boat Days and the Sacrifice

Ever since I first started coming out in 2000, I have heard about how the best birds are always found on Boat Days. Why should it matter that good birds are found on Boat Days you may wonder? The reason is that it takes time to properly document a rare bird, and we all want to enjoy the arrival of something new and unusual without having to focus all of our attention on pulling off a smooth boat landing. But the Boat Days provide us food and other necessities, and therefore, take priority over the birds. There is a precedent for this Boat Day superstition. Birds like the Red-faced Warbler, Alder Flycatcher, Red-flanked Bluetail, and last year’s Yellow-breasted Bunting were all found on Boat Days. But there were also many great birds that were not found on boat days such as the Lanceolated Warbler and Olive-backed Pipit. As is the case for most superstitions, positive circumstantial evidence is strongly remembered, while negative evidence is forgotten or ignored.

And then there is the Sacrifice – this occurs when somebody who has been on the island for a long time leaves, and then a really good bird shows up. This has happened to me several times when I leave for my break in mid-October. But I have also seen many good birds while still on the island. So again, this is another example of a Farallon superstition that we all love to distort into reality.

When I returned to the island from my two-week break on 23-Oct, my friends Matt Brady and Oscar Johnson were headed home after lengthy stays on the island. The superstitious ones of us were all expecting that a mega-rarity would be found soon afterwards. With a major storm raging outside, though, most birds were leaving, and we found very few arrivals. The strong northwest winds that followed the storm continued to keep migrants away until the wind slackened on the 27th and 28th, just before the arrival of the next big storm. With light east winds, we found several new West Coast songbird migrants such as Fox Sparrow and Northern Mockingbird. A flock of five Great and two Snowy Egrets flew by the island; without a marsh, the Farallones do not provide ideal foraging habitat for herons and egrets, so these birds made a big lap around the island and headed back to the mainland. Palm Warblers are continuing to come out to the Farallones in good numbers; so far we have recorded 37 arrivals, 30 of which were banded. We found a gray-headed Orange-crowned Warbler that is either from the intermountain race called orestera or the northern taiga form called celata. The strong yellow color on the chest, light yellow on the throat, and strong eye arcs are marks that are more in favor of orestera, but the bill length was 1 mm too short for orestera and fit better for celata.

Late on the 28th, Elizabeth Ames found a young male Summer Tanager hunkered down in a chute on the north side of Lighthouse Hill. Summer Tanagers have averaged one per year on the Farallones, but somehow I had managed to miss them over the last several years. This one was a molting juvenile male, with mostly yellow plumage and few, scattered red feathers. Two days later Elizabeth found a female Summer Tanager at Corm Blind Hill. It’s funny how a bird can elude you for years and then suddenly you see two in three days.

On 1-Nov, the Giants won the World Series, and we had our high count of the year for Brown Pelicans at 95. This has been one of the worst years ever for Brown Pelicans. Usually, pelican numbers peak at around 2000. One theory for their decline is that their prey species has declined in the area and the birds are foraging elsewhere. This seems likely for the adults, but the ratio of adults to young is about 60 to 1. So what happened to the last breeding season? The lopsided ratio seems to suggest that there was nearly complete reproductive failure.

The following day, the fog rolled in shortly after dawn. Before the island vanished, though, a few birds were able to find it such as American Pipit, Lark Sparrow, and Eastern Phoebe. All these birds showed up at the lighthouse for brief appearances and then disappeared before anybody else could find them. Fortunately, another (or the same) Eastern Phoebe showed up two days later.

After a few days of dense fog, we experienced excellent weather for attracting migrants – light east wind, overcast skies, and visibility of just 7 miles. On 5-Nov, we found a Tennessee Warbler at the lighthouse whose diet consisted of at least one spider as shown in the photo below. Later in the day, Dan Maxwell found an Indigo Bunting in the Rixford Tree, a Monterey Cypress planted in honor of the first Farallon Patrol skipper.

On 6-Nov, Dan Maxwell’s final day was upon us. Dan arrived on 11-Sep and was on the island for eight weeks. Noah Strycker predicted that Dan would see either zero or two new island birds on his last day. While the rest of us were cleaning the house and getting ready for the landing and Dan’s departure, Noah called down on his radio that he had found a Scarlet Tanager on Lighthouse Hill. This is a very rare bird on the Farallones and anywhere else in California. The rest of us all climbed the hill and got great looks at it. This was Dan’s first new island bird. Shortly after seeing the bird, the sailboat arrived and the landing began. While watching the boat pull up to the East Landing ball, a pair of adult Ancient Murrelets swam between us and the boat. Noah was right, this was Dan’s second new island bird, and just moments before he would get on the sailboat. Since the entire boat crew wanted to tour the island, I put Dan on the boat with Elizabeth, while Erika Taketa and I ran the landing.

At one point, Erika pointed out a bird flying overhead. I got a quick glimpse of it and heard it give a distinctive rattle call. I told her that it was a longspur, probably Lapland, and that she should go look for it on the Marine Terrace, a flat area with dead, matted-down vegetation. She took a quick look, but could not relocate it. After the sailboat left, I saw Noah and suggested that he should look for the longspur because it could be a Smith’s Longspur. This is a very rare species in California, and I didn’t really believe that it was one, but instead I was trying to encourage Noah to look for it and consider the possibility. A half-hour later, Noah came back into the house and showed me some photos that he had taken of the longspur. We tried to convince each other that it was just a drab Lapland Longspur, “the bill seems too big for Smith’s” and “the spacing of the primaries isn’t right.” But the drab greater coverts and buff-colored belly were not right for Lapland Longspur either. Eventually I decided that I needed to see this bird to be on the safe side. I brought my camera along, and Noah and I got many really good photos of it that show it to be a Smith’s. This was the first time this species had been seen on the island, and just the 8th time it had been seen in California! Ironically, I had included Smith’s Longspur just two weeks previously on my top 10 list of new species for the Farallones. This bird has now been here for three days! So, do good birds show up on Boat Days? Was Dan the Sacrificial Lamb? Or, are these just silly superstitions?

Written by Jim Tietz

PRBO Farallon Fall Biologist

Birds And Sharks (And More Birds)

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As fall rolls toward winter, we’re socked in fog and sideways rain. Bleak weather on this isolated rock! Check out the Cal Academy webcam (link at upper left) – maybe later; right now it just shows a wall of gray.

We can’t complain, since the last week brought good vagrant weather and a nice wave of birds. While fall biologist Jim Tietz took a couple weeks off-island (replaced temporarily by Pete Warzybok, the spring/summer biologist), our crew worked hard to keep up with a steady flow of transient landbirds. October 18th was a particularly awesome day: 107 new arrivals were banded between breakfast and dinner. (A matter of expression; we didn’t even have time to eat.)

And we’ve seen some bloody spectacular shark attacks. The local Great Whites are now collectively chomping almost a seal a day. During the fall season, we take rotating 2-hour shifts at the lighthouse with a spotting scope to record and observe shark attacks, and those shark watches are getting interesting. Last week we were able to position and focus the webcam on a full-scale attack in progress off Sugarloaf. Matt Brady, fresh off the island after spending a couple months here, somehow picked that moment to check the website from the mainland, and watched the action from afar (!). A sighting of seven Orcas yesterday, however, has the shark enthusiasts worried: in past years, all the Great Whites have cleared out after close encounters with killer whales. In at least one well-publicized instance, Orcas caught and ate a large shark here. So we’ll see what happens.

Some bird highlights since the last update (*=banded): Clark’s Grebe, Black-legged Kittiwake, Least Flycatcher*, Mountain Bluebird, Townsend’s Solitaire*, Gray Catbird*, Sage Thrasher*, Magnolia Warbler*, 4 Black-throated Blue Warblers*, Hermit X Townsend’s Warbler, Blackpoll Warbler*, 10+ Palm Warblers*, Brewer’s Sparrow*, Clay-colored Sparrow*, Grasshopper Sparrow*, Slate-colored Junco, Chestnut-collared and Lapland Longspurs, Tricolored Blackbird*, and Hooded Oriole*.

It's too hard to choose, so we'll just throw down a whole bunch of recent photos (click to view full size). Enjoy!