Migrant Activity on Mount Diablo

Ethan Monk <z.querula@...>

Hi All,

Yesterday on Mount Diablo, I hiked from the Summit Trailhead (Upper Bridge Loop)->Green Valley Regional Trail->Macedo Ranch Staging Area->Pine Canyon->Castle Rock Park. Overall a hike of about 7 miles. I had some notable migrant sightings along the way including 4 Cassin's Vireos (3 singing) on Summit Trail (1), Pine Canyon (2), and Castle Rock (1). As well, I tallied 17 Blue-gray Gnatcatcher, with 10 of these all within one mile of chaparral on the Green Valley Regional Trail, and 6 Pacific-slope Flycatchers, all of which have arrived within the past week or so. A Wilson's Warbler was flitting around at Macedo Ranch, and my first of season (overdue) Warbling Vireo was singing and 6 Orange-crowned Warblers hung around with it in the riparian willow corridor in Pine Canyon. Two weeks ago I counted 15 Orange-crowned Warblers here--13 in one spot: It seems as though these numbers have declined a fair bit since then. In a stand of Eucalyptus off Green Valley Road, I counted 7 selasphorus hummingbirds, presumably mostly Rufous considering the time and location. I also had 2 singing Townsend's Warblers, both probable migrants on Mount Diablo: They rarely winter on the mountain. As well, the Harris's Sparrow did not continue at Castle Rock Park. It's good to know that Spring is back!

Also of note, in my yard (Alamo), on the 2nd, I photographed a probable Hammond's Flycatcher, this would be the second Spring arrival of the year in NorCal. From what I can work out, this is the third earliest Spring record of this species in Contra Costa and also the East Bay (I assume the Hammond's Flycatcher at Garin Regional Park between 2010-12 was one bird returning for consecutive winters but the lack of winter reports were generally due to a lack of coverage and/or the bird being more reclusive during the colder times of year? Correct me if I am wrong...) The only earlier records I can find are on the 31st of March in Mitchell Canyon per Steve Glover in 1995, and the 12th of February, 2017, at Hayward Regional Shoreline per Bob Richmond. While my bird could presumably be a Dusky, it seems rather early and this bird did not strike me as a Dusky/Least Flycatcher in the field. Then again, I haven't seen too many of either of those species. For now this is tentatively IDed as a Hammond's considering the date and my general proximity to Mount Diablo. Feedback welcome.
Photos here: https://ebird.org/view/checklist/S54479337

Good birding,
Ethan Monk

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