Date: 9/8/26 1:23 pm From: Dominik Mosur via groups.io <dominikmosur...> Subject: Re: [EBB-Sightings] San Ramon area migrant notes and Pleasanton Kite Roost - Labor Day Weekend (9/6 and 9/7 2026)
A quick addendum to the Kite report. If you do come out to observe please
be respectful of the residents in the neighborhood. Don't block
driveways/sidewalks, point big lenses into people's homes etc.
DM
SF
On Tue, Sep 8, 2026 at 1:22 PM Dominik Mosur via groups.io <dominikmosur=
<gmail.com...> wrote:
>
> I spent Sunday 9/6 birding around San Ramon (Contra Costa County) to see
> what signs of migration could be detected in the suburbs and yesterday
> reprised a 7/20 hiking loop of Las Trampas Regional Wilderness along Rocky
> Ridgewith the same goal.
>
> Overall numbers of migrants were lower than I had anticipated/hoped for
> but there were still a few things that I found notable enough to share with
> the list. One thing I found interesting was that while my weather app
> indicated a 2-5 mph Northeast wind in San Ramon, Rocky Ridge (elevation
> ~2000') was blown out at a steady 15-20 mph with gusts so strong that I had
> to hold on to my scope to keep it from getting knocked over.
>
> Vaux's Swift - a loner flew over the Las Trampas main staging area with 3
> unidentified Swallows early in the morning. I was hoping the Northeast
> winds would bring more but that was it in ~5hrs. It was the first one I've
> seen this fall
>
> Say's Phoebe - singles were on the Iron Horse Trail and at Old Ranch Park
> in San Ramon. Early September is when Say's start to arrive for the
> fall/winter season but in recent years I've noted them breeding just a few
> miles east of here so these may be locals
>
> Violet-green Swallows - 3 flew over Rocky Ridge/Las Trampas ,the first
> ones I've seen this fall
>
> Red-breasted Nuthatch - the region wide irruption was in full evidence
> with several calling from the oak/bay stands along the Las Trampas
> Elderberry Trail. (2) flew past me on Rocky Ridge from the Watershed lands
> heading down into the canyon
>
> House Sparrow - a flock of (~20) along the Iron Horse Trail next to
> Montevideo Elementary were notable to me because it's the first time in
> dozens of efforts going back to 2021 that I have encountered this species
> within San Ramon City Limits. MINDBLOWING!
>
> White-crowned Sparrow (Pugetensis) - a somewhat early migrant HY
> White-crown was along the Iron Horse Trail at Pine Valley Rd.
>
> Rufous-crowned Sparrows - 4 pairs noted along the Rocky Ridge/Elderberry
> Trails in Las Trampas were all in spots where I seem to encounter this
> species on every visit. It appears that similarly to California Towhees,
> Rufous-crowned Sparrows maintain a territory and pair bond year round
>
> Tricolored Blackbirds - a few of these could be heard giving their
> distinctive "what's wrong with that cat" vocalizations mixed in a flock of
> (~200) Red-winged Blackbirds on the natural turf axillary ball fields of
> California High School next to the Iron Horse trail. Another data point
> emphasizing the danger of the artificial turf conversion trend that seems
> to be so prevalent in these days
>
> MacGillivray's Warbler - a hy female in coyote brush surrounded by
> parched grassland was an obvious migrant, as engaged in a conversation with
> one of the Rufous-crowned Sparrow pairs along the Elderberry Trail in Las
> Trampas. It was my first encounter with this species ever in Contra Costa
> County since I refuse to bird Mitchell Canyon or the Berkeley Hills on
> general principle.
>
> I also wanted to pass on a report of an amazing spectacle taking place in
> Alameda County in Pleasanton in the past two weeks. Starting 8/28, fellow
> EBBirder Isabelle Reddy has been noting a massive White-tailed Kite roost
> gathering in the vicinity of Ken Mercer Sportspark and Woodthrush Park.
> Isabelle noted 20 kites the first evening 8/28, 78 on 9/1,133 9/3, 175
> 9/4, 224(!!) 9/5, 142 9/6 and 112 9/7. Per Isabelle the roost appears to
> have shifted as of last night but the kites keep coming each evening
> starting about an hour before sunset and quickly departing around first
> light the following morning. Isabelle will be out of town for a while but I
> would encourage other birders/citizen scientists to come by and continue
> the effort of counting these birds and tracking where the roost shifts to.
>
> Per eBird data this is the largest roost of White-tailed Kites in the
> United States of AMERICA!
>
> Happy Fall Birding everyone,
>
> Dominik Mosur
> San Francisco
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