Stuck Between a Rock and a Blue (or Gray) Place
September 27, 2016
There’s no denying it; those of us living on Southeast Farallon Island (SEFI) are stuck on a big rock in the Pacific Ocean. There are no mountains, no valleys, no forests, no wetlands. The sky is above us and the sea is virtually everywhere else. When both are calm, it can be hard to tell where one ends and the other begins, instilling the sense of being lost in a void of blue or gray. But comfort is found by remembering that we’re not the only one out here.
The void between the California coast and the Farallones is filled with life, particularly as we enter our fifth week of the fall season, when it is made up largely of transient species. Butterflies, dragonflies, birds and bats travel above the oceans surface, while cetaceans and sharks travel below. Many are exactly where evolution dictates they should be, while others have drifted off course, or may be misinformed by anomalous genetics. However, whether or not they reach SEFI is dependent on the nature of the void.
We tend to get the most arrivals when the winds are calm and visibility is good enough to see several miles, but still obscures the mainland. Favorable conditions for bird arrivals also tend to occur when there is a low cloud ceiling and a light southerly wind. Most landbirds and bats migrate at night, often at elevations above one thousand feet. So when they descend through the clouds in the morning and find themselves over open water, SEFI may be their only option as a stopover site. When the mainland is visible, it presents itself as a more appealing option (provided the animal has enough energy to make it there).
Nearly the entire second half of August was calm and gray, and sure enough several bird waves flocked to our rock, making it a slightly more productive August than average. Good numbers of early migrants such as Townsend’s and Black-throated Gray Warblers were in evidence, along with 98 other avian species from across North America. This monthly total includes several eastern species, such as Blackburnian, Tennessee and Mourning Warblers, Least Flycatcher, and Red-eyed Vireo. Species such as these are decidedly rare throughout western North America, but can be expected on SEFI, where migrants can become concentrated on this small island and are easily found in the limited vegetation. On the other hand, some species that are common on the mainland are significant rarities here. Cinnamon Teal, Band-tailed Pigeon, and only the island’s 10th Bald Eagle are some the highlights this fall from this group.
Among this diverse suite of arrivals, though, were a few species that were lacking in abundance. Though we’ve seen a nice diversity of flycatchers so far this fall, Willow and Pacific-Slope Flycatchers, as well as Western Wood-Pewees have been less numerous than usual. Because the presence of landbirds on SEFI is dependent on weather, it’s impossible to say whether a single season’s low numbers mean that these species’ populations had poor breeding success this year, or if it is just due to local weather patterns. Nonetheless, population trends can be detected over many years and examining long-term trends in data can be invaluable for inferring how oceanographic and climate change may be affecting them.
September has seen only a single week of calm gray weather, but it was a glorious week! So far this month, our crew has found an additional 38 species of migrants, with the beginning of a shift from warblers to sparrows. Our first slew of Clay-colored, Vesper, Fox, White-crowned and Golden-crowned Sparrows all graced the island with their presence. Though most of these birds ended up in and around the Monterey Cypresses near the houses, the lighthouse at the top of the hill seems to be where many make first landfall. It can be a spectacular treat to encounter a lighthouse flock as habitat and geography become obsolete. Chestnut-sided Warblers forage alongside Lazuli Buntings, while an Olive-sided Flycatcher perches below you at eye-level on a slab of granite. All the while Violet-green Swallows buzz around, and Merlins make occasional passes at feathered morsels.
But when the wind blows, the scene changes entirely. Strong winds make it difficult for passerines to reach the Farallones. Northwest winds are favorable for southbound migration, but pin birds to the coast or inland, and often encourage stopovers to depart. Meanwhile, strong southerlies provide a headwind, typically shutting down migration altogether. Not only are these conditions poor for bringing migrants to the island, but they also make it impossible to mistnet for the few present, and can cancel our daily vigils for shark attacks. But as many birders are aware, bad weather can occasionally mean good birds. In years past, rarities such as White Wagtail, Nelson’s Sparrow, and California’s first record of Olive-backed Pipit have all shown up during strong northwest winds, and this is more than enough to keep us on our toes during these bright yet dreary days.
And we can always look to the ocean for novelty. Though the Farallones are 30 miles from the Golden Gate, they’re still a good five miles from the continental shelf where upwellings create highly productive areas for marine life. Thus most of the seabirds we regularly encounter are inshore species like Sooty and Pink-footed Shearwaters and Parasitic Jaegers. When strong northwest winds churn up the seas, they also plant dreams in (at least some of) our heads of spotting the highly pelagic seabirds that are usually just barely out of view. Dreams rarely become reality, but the evening of September 21st was a major exception. While scanning Fisherman’s Bay that evening for gulls, I was distracted by three tubenoses not far beyond Tower Point. Two were clearly Pink-footed Shearwaters, but the other was flying much faster, making many tight zig-zags over the water but still traveling at about the same pace as the shearwaters. It was also clearly smaller. I couldn’t believe my eyes as they told me I was looking at a bird with clean white underparts, a dark cowl that contrasted with a dark brownish-gray mantle, and darker upperwing-coverts creating a weak ‘M’-shaped pattern: a Hawaiian Petrel! I was able to watch it for at least a minute as it bounced in and out of the wave troughs, and snapped some poor but useful photos in direct comparison to a Pink-footed Shearwater before they disappeared behind Sugarloaf. It seems this species is being detected more regularly off the west coast, so hopefully more sightings like this will continue to become reality.
Though the blue/gray weather dichotomy is real, it is far from absolute. Every once in a while we’ll have a perfectly calm day with blue skies, where the ocean is like a mirror and marine haze obscures the mainland from view. September 14th was like this. There were not a lot landbirds around, and arrivals were clearly lacking on our morning area search. The bird community was quiet, the weather was quiet, and the day felt particularly relaxing. A small handful of migrants seemed to pop out of nowhere—a pleasant surprise. Among them were some quality migrant birds like a stunning male Prairie Warbler from eastern shrubland, a Lark Bunting from the western Great Plains, and most unexpected of all, a Philadelphia Vireo. This latter species is particularly rare in California, so it almost seemed too easy to find one sitting in our mistnet! The blue theme of the day was further emphasized by the presence of at least four Blue Whales, lunge-feeding with Humpbacks out towards the continental shelf. It’s days like these that make one quite content with being stuck on this particular rock.
With all this having happened, the Farallon crew initiates its 25th Farallonathon on September 25th. At the end, we will provide a summary of this week-long bioblitz. If you wish to contribute, please click on the following link: http://birdathon.kintera.org/faf/search/searchTeamPart.asp?ievent=1164352&lis=1&kntae1164352=EF92FC43CF1D4F468F2053B6B284666B&team=6865041