Date: 9/24/26 9:06 pm From: Marty Freeland via groups.io <martinf3...> Subject: [pen-bird] Recent notes: Red-eyed Vireo, Blackpoll, Redstart, etc.
Hi all,
I birded parts of the San Mateo coast yesterday (9/23) and Monday (9/21), as well as Santa Cruz Co. on 9/21 and 9/22. Highlights from San Mateo included Red-eyed Vireo, Blackpoll Warbler, American Redstart, and Willow Flycatcher, and from Santa Cruz included Blackburnian Warbler, 2 Tennessee Warblers, 2 Chestnut-sided Warblers, and Northern Waterthrush. (Santa Cruz notes might be relevant context for San Mateo birders and I can't get Google Groups to work to send them to the MBB listserv, so they are tacked onto the end of this email.)
On 9/23 I birded the north coast from Pillar Point to Mussel Rock Park until 1 pm. Morris was on the inner breakwater at Pillar Point at dawn. Patchy fog burned off almost everywhere by midday and winds were light and mostly from the west. Migrant numbers were reasonably good all day. At Princeton Willows a female-type American Redstart was in a small flock along the road to Mavericks and a large flock on the back side of the willow patch (near the new construction by the mobile home park) contained seven warbler species (1 MacGillivray's, 2 Yellow-rumps, 1 yellowthroat, 2 Orange-crowns, 2 Wilson's, 5–6 Townsend's, 6–8 Yellows). Another MacGillivray's was at the Farallone Willows in Montara. At lower San Pedro Ck the flock closest to the parking area had a Cassin's Vireo and a beautiful HY Red-eyed Vireo. I was surprised to find only one flock along the length of Calera Ck and even more surprised that it contained no Yellow Warblers. A Western Wood-Pewee was at Mori Pt and a Willow Flycatcher, quite scarce in San Mateo and especially so coastally, was in the interior willow basin at Mussel Rock Park. Mussel Rock is a great location for Willow Flycatcher and this has been a good year for them in the county, with this being the 8th individual. In some falls there are just 1–3! Driving out of Mussel Rock Park I heard a flock and pulled over to check it. I was happy to see a nice HY Blackpoll Warbler, my first in Pacifica and a species that has become much less regular in the county. Other locations I checked included Denniston Ck, Fitzgerald MR, San Vicente Ck at Etheldore, Sunshine Valley Rd riparian (both ends), and Pedro Pt.
On 9/21 I started at Ano Nuevo under a high overcast and light NW winds, where excellent numbers of common western migrants included more than 30 Yellow Warblers, 6–8 Western Flycatchers, and so on. A pulse of Yellow-rumped Warblers was also evident. An Acorn Woodpecker immediately south of Ano Nuevo was likely from this species' most coastal outpost in the county less than a quarter-mile to the northeast, but it was the first time I have seen one at the actual seashore in San Mateo. At least three Black-vented Shearwaters offshore were visible from the same spot. For the rest of the day I birded Santa Cruz, where migrant numbers were not that great (probably because all the migrants were in San Mateo!) and it got very windy by noon or so. A Tennessee Warbler was west of the highway in Davenport. Otherwise nearly all of the flocks I located contained 0–5 migrants in total until I got to the vicinity of Natural Bridges, where there were two Chestnut-sided Warblers (with different flocks) at Antonelli Pond and a dull Blackburnian Warbler with a large flock in a small willow patch northeast of Delaware x NB Dr. San Mateo has now had 3 Blackburnians so far this fall and 2 Blackpolls, while Santa Cruz has had 2 Blackburnians and 0 Blackpolls: it will be interesting to see how these ratios end up by the end of the season!
On 9/22 I birded southern Santa Cruz until 1 pm under a high overcast south of Aptos and with NW winds becoming quite strong by noon or so; migrant numbers were good except on the Pajaro River itself, which was very slow. Two Pectoral Sandpipers were together at College Lake and the eucs behind the church had at least 20 Yellow Warblers. There was a cooperative Northern Waterthrush on upper Struve Slough that spent some time in coast live oaks across the trail from the wetland. I think a waterthrush in coast live oak is a first for me! Stopping at willow patches along San Andreas Rd, a Townsend's Warbler with a pigment-deficient pinkish-yellow bill was at Crestview Dr and another Tennessee Warbler was at San Andreas Rd x Altivo Ave. A Cassin's Vireo was at Hidden Beach CP.
Many of the Orange-crowned Warblers I have seen in the Bay Area this season have been dusky dullish birds with smudging on the undertail coverts, often lacking the bright greenish tones typical of lutescens, and it sounds as though others have had similar experiences in San Francisco and elsewhere. However, few if any have been bona fide sordida. To be claimed as sordida it's not enough for a bird to be duller than the typical lutescens; it should really tick all the boxes. (These subspecies also differ in size, bill structure, call, etc., not just undertail covert pattern.) Range expansions by both lutescens and sordida in SoCal, where sordida breeds not just on the Channel Islands but also on the mainland in sympatry with lutescens, have probably increased the frequency of intergradation substantially in recent years, and that may be a plausible origin for all these dusky birds we are seeing, but it's hard to be certain. Likewise, there have been a few gray-headed Orange-crowns (orestera/celata) around, although I have not seen not nearly as many so far as I had in the past two falls by this date. Another cautionary note on identifying these subspecies is that Orange-crowned Warblers may be sexually dichromatic with respect to head color (with females showing grayer heads), though opinions vary on this. Anyway, good photos and detailed notes are helpful if trying to identify Orange-crowns to subspecies, and regardless the coarse Orange-crowned Warbler label sans subspecies is very often the best option.
