Aside from the Yellow-browed Warbler in Moss Beach, highlights from a fair amount of coverage over the past ten days or so in San Mateo included Hooded, Blackburnian, Black-and-white, Palm, and Tennessee (3x) warblers, a White-winged Dove, a Yellow-headed Blackbird, a somewhat early Slate-colored Junco, a handful of Nashvilles and FOS White-throated Sparrows and things, a very surprising unseasonable pulse of Swainson's Thrushes, and (presumed) last-of-season Western Flycatcher, Wilson's Warbler, and so on. Red-breasted Nuthatches have died down somewhat and are about half or two-thirds as numerous as they were three weeks ago. Red Crossbill numbers have really picked up, however, and they are nearly everywhere. So far, all the crossbills I have heard have sounded fine for Type 2 to me, which seems to be the dominant type locally in this year's irruption.
On Tuesday 10/13, I started at Mori Pt, where phenomenal numbers of sparrows at dawn included the first White-throated Sparrow I have noted in the county this fall. (I also had one the previous day in Santa Cruz.) I left San Mateo Co. briefly to go see the Sulphur-bellied Flycatcher in S.F., which was a walk-up bird, and then birded the rest of the north coast from Thornton SB to Montara. A Warbling Vireo and two Yellow Warblers were along upper Calera Ck. Entering the willows at lower Calera Ck, I heard a Northern Waterthrush chipping and while trying to pish it in for views, I heard a different sharp thin chip note and eventually got good views of a bright Tennessee Warbler. Shortly afterward I learned that the waterthrush had been found four days previously by Cédric Duhalde. Meeting up with Cédric, we birded the Farallone Willows in Montara, where Cédric spotted a Nashville Warbler. Two were together here on 10/5. Singles of Western Flycatcher on lower Sunshine Valley Rd and Wilson's Warbler along Pilarcitos Ck behind the lowest pumpkin patch were the only other Neotropical migrants I had all day.
On Thursday 10/15, I found few passerine migrants in a full day of coverage of the central coast from Pescadero to Half Moon Bay under clear skies all day, with a light NW breeze in the morning picking up substantially by midafternoon. A group of about 25 Greater White-fronted Goose flew out of Pescadero Marsh at dawn. A single Yellow Warbler and a Nashville Warbler were behind the gas station in Pescadero, where two Nashvilles were on 10/7. A Palm Warbler, my second this fall in the county, was along Butano Ck Cutoff near the high school. The sole Neotropical migrant on all of Tunitas Ck was a getting-late Swainson's Thrush near the mouth; a Black-crowned Night Heron at the same spot was notable locally. At the Johnston House I had my second White-throated Sparrow of the fall in the county, and a Warbling Vireo was behind Mariners Church in Half Moon Bay. Yet another Nashville Warbler was along Pilarcitos Ck at Oak Ave Pk. I saw relatively few (c. 5) Red-breasted Nuthatches all day.
On Friday 10/16, I birded north Half Moon Bay from Pillar Point to Miramar in the morning. The conditions were bizarre with a fairly strong gusty east wind and very high temperatures, 74 şF in Half Moon Bay before sunrise (!). Morris the Northern Gannet was present on the inner breakwater. At Princeton Willows, a striking female Hooded Warbler popped out near the western end of the patch and right off the road to Mavericks in response to pishing. This was a long-awaited self-find in the county! At eight more stops in northern Half Moon Bay I had zero additional Neotropical migrants.
On Saturday 10/17, I birded the south coast from Weed Farms to Pescadero in the morning. Weed Farms was below its usual standard, being dry with low sparrow numbers. However, the fields north of Cascade Ck have been burned again; while they had few open-country birds on this day, after the last burn a couple years back these fields were extremely productive, and they should be checked through the next couple months for longspurs, Horned Lark, and similar. Excellent sparrow numbers at Pie Ranch included a junco showing characteristics of the Slate-colored group. (I think of the Slate-colored group as encompassing both Boreal Slate-colored, hyemalis/carolinensis, and Cassiar Slate-colored, cismontanus; for female-types like this bird I generally prefer not to say anything more specific than Slate-colored group in the broad sense, absent excellent photos etc.) This is a rather early date and indeed I do not know of many documented records for the county before October 20, though I am sure there are some older ones of which I am not aware. I was surprised to learn that ridgewatchers in Marin, Santa Cruz, and elsewhere have reported Slate-colored Juncos this year starting on September 30. No doubt these are side effects of increased coverage aimed at irruptive montane birds, but it is still interesting. I average 1–2 Slate-colored Juncos per year on the San Mateo coast, usually in Nov–Dec. Also at Pie Ranch was a Warbling Vireo, and a Black-throated Gray Warbler was along Whitehouse Ck at Costanoa. Along lower Gazos Ck, birded from the gas station parking lot, a very dull Blackburnian Warbler was with a small flock. I think that puts the tally at 6–6 Blackburnian–Blackpoll this year in the county. Still a little while left for one of them to pull ahead and break the tie!
On Sunday 10/18, Chris Henry and I started at Ano Nuevo, where we had single Yellow and Black-throated Gray warblers, as well as several flocks of Red Crossbills, including on the outer part of the peninsula. I believe most or all were Type 2, as most of the invaders have been this fall. We then birded Santa Cruz Co. for ten hours and had nothing better than a single Palm Warbler because Santa Cruz is not as good a county as San Mateo is. To prove the point, while we were off seeing no birds in Santa Cruz, Ryan Mense found a beautiful male Black-throated Blue Warbler at the previous day's Blackburnian spot :)
On Monday 10/19, I birded pumpkin patches and odds and ends for sparrows and weedfield birds around Half Moon Bay for most of the day. Numbers of Golden-crowned and Lincoln's sparrows were very low, especially with far fewer Lincoln's (8–12 all morning) than expected by this date. Among the very numerous White-crowned Sparrows were several Gambel's, including three together at Andreotti Family Farms. One each of Nashville and Yellow warblers were at the Farallone Willows in Montara. A couple scattered Red Crossbills were all Type 2, I think. An access point to Pilarcitos Ck that I rarely check, along the north side by Hwy 92 x Hwy 1, had a large flock that included a nice-looking female Black-and-white Warbler.
On Tuesday 10/20, I started in San Francisco and spent far longer there than expected because Caitlin Chock and I had a Yellow-green Vireo and a Blackburnian Warbler in the arboretum. Rushing to get through a couple spots on the northern San Mateo coast on the way back, a Yellow Warbler was at Thornton SB and the Northern Waterthrush discovered on 10/9 by Cédric Duhalde was still at Calera Ck.
On Wednesday 10/21, I birded the central coast from Pigeon Pt to Half Moon Bay under high overcast and light shifting winds for the most of the day, strengthening with a couple light rain showers in the late afternoon. At the residences on eastern Pigeon Pt Rd, a White-winged Dove was with Eurasian Collared-Doves on the wires and a calling Northern Mockingbird was down near the small pond. Northern Mockingbird is rare on most of the San Mateo coast, but one was at this same location last December. At Pescadero Marsh, a Blue-gray Gnatcatcher was with a small flock in the riparian and I was surprised to hear a Swainson's Thrush calling. I was still more surprised to hear another Swainson's Thrush along Butano Ck and then others on San Gregorio Ck, at the Verde Rd Pond, and two (!) along Miramontes Ck. I had a late on 10/15 and otherwise none since 10/6 in the county, so having a minimum of six individuals today was truly astonishing. To make sure I had not developed a recurrent Swainson's Thrush auditory hallucination, I worked hard to obtain views of the calling bird at Miramontes Ck and only in doing so did I realize two individuals were present. A late pulse of Swainson's Thrush like this one is very interesting and quite noteworthy. Possibly related were single birds reported the following day (10/22) on Corona Hill, SF, and on Southeast Farallon Island. Reaching Pescadero, two Tennessee Warblers were together (more or less; each seemed to staking out one bush) in bottlebrushes near the end of Water Ln and an adult male Black-throated Gray Warbler was at the Stage Rd bridge over Pescadero Ck with a large flock. A Nashville Warbler was along Tunitas Ck just above the dip. Red Crossbills were noted at Water Ln, Goulson St, San Gregorio Ck, and Mariners Church. The blackbird roost along Verde Rd had more than five times its usual number of blackbirds, even when I stopped at 2:20 p.m., well before the usual peak time. Scanning through these I noted a high proportion of Tricolored Blackbirds with at least 1,500 individual trikes in 2,000–2,500 total blackbirds. The remainder were mostly Red-wings, with a couple dozen Brewer's and a single Yellow-headed Blackbird. The Yellow-headed was a bright HY bird and only the second I have seen on the San Mateo coast.
On Thursday 10/22, there was a heavy low overcast with rain showers over the central coast, so I started in neighborhoods in El Granada. I rarely visit these neighborhood patches before November. Passerine numbers were a little lower than usual in these locations, but that may be a result of the early date. At Princeton Willows, I relocated the female Hooded Warbler from last week, deeper in the willows, and others also relocated it the following day (10/23). With a weeklong stay at this late date, there is a chance this bird may attempt to winter. Checking neighborhoods in Pillar Pt Bluff southwest of Fitzgerald, a Palm Warbler was at the corner of Park Way and Orval Ave. Then I checked upper San Vicente Ck at Ember Ridge and lightning struck with a beautiful Yellow-browed Warbler. Details on the Yellow-browed Warbler are on eBird and elsewhere and will be submitted to the CBRC.
On Friday 10/23, I spent much of the day seeing the Yellow-browed Warbler with others, but also birded other locations on the central coast between Pillar Pt and Hwy 92. A group from San Luis Obispo including Kilian Hampl, Reef Comer, Ann Stockert, and perhaps others found an immature Yellow-crowned Night Heron at Pillar Pt; this is the fifth county record and the first away from Coyote Pt and Ano Nuevo, which have two records each. Morris was present as well. A Black-throated Gray Warbler continuing from the previous day at the Yellow-browed Warbler spot was the only Neotropical migrant all day.
