Just as we were about to leave, news came over the radio from Kristie Nelson that a sapsucker was on Lighthouse Hill. Three of the four species of sapsuckers had already been seen on the island: these were the Red-breasted, Yellow-bellied, and Red-naped Sapsuckers, each with several records on the island, but still quite rare. As we tried to figure out over the radio which species it was, Cameron, who had been having radio problems, finally got through that it was a male Williamson's Sapsucker, a first island record for this species. Whereas the other three species of sapsuckers have breeding ranges that extend well to the north and annually undertake long-distance southward migrations during the fall, Williamson's is a montane species that mostly migrates downslope for the winter, and interestingly, there are no coastal records north of the San Francisco Bay Area. Needless to say, we quickly postponed our trip to West End Island so we could enjoy this new island bird and help document the abundance and diversity of these newly arrived migrants. Unfortunately, the sapsucker flew to the west soon after we shot a few documentary photos and was not relocated afterwards.
For the next hour, we searched for the sapsucker along the cliffs on the western side of the island, and looked through the flocks of sparrows, thrushes, and kinglets to increase our species list. It quickly became apparent that this bird wave was almost entirely composed of western species, especially Golden-crowned, White-crowned, Fox, and Savannah Sparrows, Hermit Thrushes, Audubon's Warblers, and Ruby-crowned Kinglets. Normally, large bird waves on the Farallones are associated with a few to several stray eastern vagrants, but despite much searching, the only "eastern" birds we could find were singles of White-throated Sparrow and Yellow-shafted Flicker. Although both of these species winter more commonly in the East and are thus considered "eastern", their breeding ranges extend quite far west in Canada and a decent number winter in California as well.
The person conducting the island-wide area search this morning had a much busier day than the few days previously when we were only seeing a few individuals of a few species. On this day, Luke Musher recorded dozens of individuals of 34 species. To help us determine numbers of arrivals and to track individuals over time, we also banded as many birds as we could safely capture in our mistnets. By the end of the day, we had banded 146 birds of 21 species. As with the area search, Golden-crowned, White-crowned, Fox, and Savannah Sparrows, Hermit Thrushes, and Ruby-crowned Kinglets were the most abundant. Hammond's Flycatchers are an uncommon species on the Farallones, so we were quite surprised to capture three of these birds. Probably the most interesting thing we discovered through banding on this day was the preponderance of adult birds to juveniles. Along coastlines, juveniles typically outnumber adults by a large margin, so whatever caused this massive misdirection by adults must have been pretty unusual.
This bird wave also produced a few subspecies that have rarely been seen before on the island. The most interesting were within the Fox Sparrow complex. There are at least 17 subspecies that have been recognized in this species, and they have been lumped into four groups based on geographical proximity and morphological and genetic similarity. Although Thick-billed is the only group with a widespread breeding distribution within California, this is the only one that we failed to see. Sooty Fox Sparrow is the most common winter visitor to California. It breeds from southwestern British Columbia north through southern Alaska, and we determined there were at least 80 of these on the island. We also found three Slate-colored Fox Sparrows, which breed in the Rocky Mountains and Great Basin. Although they winter in California from the Central Valley south to Southern California, they are scarce along the Northern California coast, and there are few records for the Farallones. The individual photographed here appears to be of the Alberta subspecies, altivagans. This subspecies is morphologically intermediate between Slate-colored and Red, but genetically it falls solidly within the Slate-colored group.
Red Fox Sparrows breed in northern Canada and northern Alaska, and they winter in the eastern United States. This is a casual vagrant to California, so we were excited to find one in a mistnet and another that Dan later captured with his camera! This individual appears to be of the zaboria subspecies, which occupies the western half of the Red Fox Sparrow range during the breeding season. Note how much more red there is in the crown, face, and back of the Red below compared to the Slate-colored above.
Another interesting bird seen this day was a Song Sparrow that wandered about the intertidal. The subspecies of this bird is thought most likely to be fisherella, which breeds in drier habitats from northeastern California to British Columbia, but could possibly be the montana subspecies of the Great Basin- either way it would be a first for the island.
We also had a continuing Burrowing Owl, Peale's Peregrine Falcon, Sandhill Crane, and Blue-footed Booby. The latter was either the continuing third bird (see our previous blog post about Blue-footed Boobies) or our fourth for the fall season.
In addition to birds, we also added a point for a rather rare butterfly to the Farallones called a Common Buckeye.
At the end of a lengthy evening journal, we determined that we had observed a total of 826 landbird individuals of 51 species - including waterbirds, we saw 75 species. After adding up all the points we got for birds, pinnipeds, whales, butterflies, dragonflies, and bonus points for first island records and California Bird Record Committee review species, we found that we were doing quite well for our first day with 110 Farallonathon points. If you would like to contribute to our research on the Farallon Islands, please visit our donation page at the following link: