Morning flight (visible migration) around Mount Diablo and Morgan Territory (long)
Inspired by reports of spring morning flight, also known as visible migration, elsewhere in the state, in which 10s, 100s, or in a few cases 1000s of birds can be seen flying by low to the ground in just a few hours after sunrise, I decided to try to find good local sites to observe this. Ridges seem to be the most common location for observing these flights in the state, so the challenge is finding publicly accessible ridges that don’t require a long hike to reach given that the flights typically last for only a few hours after sunrise. In addition to a ridge location, it seems that good sites often experience headwinds that force the birds to fly close to the ground as they clear the ridge.
The only sizable morning flights that I could find reported in the Mount Diablo area were from Mitchell Canyon/White Canyon in April 2020 (Logan Kahle, John Toldi, Eli Gross, Ted Robertson). I don't believe any large flights were seen here in spring 2021 despite extensive coverage as usual each spring (let me know if you did!), so perhaps it was an atypical weather pattern in 2020.
In reviewing Google Earth, wind patterns of nearby weather stations (see mesowest.utah.edu for many weather stations), and the regional trail map (see Save Mount Diablo website for this), I decided to explore the following locations (lat/long coordinates included). Note that I've only visited these sites once or twice so far and for only an hour or so at a time, so I'm not sure what these sites will be like as migration progresses and with different weather conditions.
Highland Ridge--gate saddle (Morgan Territory) (37.839896, -121.841630)
Morgan Territory interested me as it borders extensive grasslands to the south that wouldn't be suitable stopover habitat for many passerine migrants, so perhaps there would be a morning flight of migrants searching for habitat within Morgan Territory. This site is a slight saddle near a gate toward the northwest end of Highland Ridge at 1700 ft elevation. Spring winds show a mix of directions but often from the N/NW or S/SW.
On 4/7 7:40-8:40 am with a north wind, 131 birds passed northward over the ridge including 15 adult male Rufous Hummers, 29 hummer sp., 8 Western Kingbirds, 32 Yellow-rumped Warblers, 1 Black-throated Gray Warbler, 1 Phainopepla, 2 Lawrence's Goldfinches, and others. Highland Ridge is above 1700 ft for over 5 miles to the southeast of here, and it looked like some birds were being funneled along its western slopes as they looked for a low spot to cross. Birds were also flying up the Tassajara Creek tributary canyon from directly below the saddle to cross. There are oaks just below the ridge on its south face, and it was interesting to watch birds fly up from the canyon bottom until they encountered the north wind, drop down into these oaks, and wait for a pause in the wind to try to cross.
Park off the road at 37.851503, -121.847249 and don't block any of the gates. Hike up Morgan Ridge Road for just over a mile and 800 ft elevation gain to reach the site.
Highland Ridge--Black Hills saddle (37.840497, -121.848570)
This site is just west of the gate saddle and about 1500 ft elevation. The Black Hills Trail runs parallel to the site here but downslope. I have not yet had a chance to observe from this site, but while watching from the gate saddle, I noticed some birds deciding not to try crossing at the gate and heading west presumably to cross at this lower saddle. Access is the same as the above but go west upon reaching Highland Ridge instead of east.
Highland Ridge--Old Finley Road saddle (37.847259, -121.860733)
This saddle is also on Highland Ridge at 1500 ft elevation and further west from the above two sites, and I thought birds flying up Riggs Canyon may cross here instead of flying over Windy Point at 2100 ft. On 4/8 7:35-8:25 am with a southwest wind, 115 birds passed over this site including 62 Yellow-rumped Warblers, 11 Pine Siskins, 4 Lawrence's Goldfinches, and others. To my surprise many birds were flying south or southwest here into Riggs Canyon instead of flying out of the canyon. Not sure how weather dependent this is or whether flight directions are consistently mixed at this site. Park at the same spot as the above but hike for just over a mile on Morgan Creek Road and the Jeremiah Trail with about 600 ft elevation gain.
Mallory Creek canyon (Morgan Territory) (37.819473, -121.791187 and 37.818778, -121.780086)
On March 26 two locations were checked for birds flying up this canyon with the first spot at the top of the canyon and the second on the eastern slope to look down into the canyon. No birds were seen flying through, though this was probably due in part to the early date. Winds are often from the west here in spring. Park at the staging area and hike out on the Volvon and Whipsnake Trails.
Prospector’s Gap (Mount Diablo) (37.887314, -121.908712)
This is the saddle between the main summit and north peak and seemed like a logical location for birds to fly through (2900 ft elevation) if they're trying to clear the mountain while avoiding flying over the two peaks (3800 and 3500 ft elevation). Winds are often from the north or northwest here in spring, so presumably birds would be more inclined to fly low to the ground given this headwind but also because they may still have to climb elevation to clear the gap. On 4/10 with a strong >20 mph northwest wind, there were 2 hummer sp. and 2 passerine sp. that flew over here. Perhaps winds were too strong for birds to bother flying all the way up here? Park at 37.879717, -121.914010 and hike east around the main summit and down to the gap. The north gate park entrance is often open at 7 am.
Perkins Canyon (Mount Diablo) (37.897104, -121.880313)
This spot is on the northeastern flank of north peak and seemed like a possible location to concentrate birds trying to get around the mountain that don't want to fly up and over Prospector's Gap or the two peaks. This area also often experiences north or northwest winds in spring. Birds could also get around the mountain via its west side, but winds here in spring are often from the southwest or south and therefore more of a tailwind that might not push birds down close to the ground. I did not check out any sites on the west side of Mount Diablo to test this. Unfortunately no birds were seen flying by this site on 4/6 with a north wind. Park at 37.903940, -121.874308 and walk south along the trail that follows the road then west up the mountain for about 500 ft elevation gain in just under a mile.
Three Springs staging area (Mount Diablo) (37.911478, -121.884171)
I had the same idea as with Perkins Canyon to see if birds would fly around Mount Diablo past this site, but no movement was observed this morning 4/12 with a north wind. Park off the road at 37.912500, -121.885464 and don't block the driveway.
Morning flights typically continue through at least the middle of May elsewhere in the state, so I'd be interested in hearing your experience if you go to the above sites or anywhere else in the Bay Area to witness this spectacle.
Thanks, Michael, this is great stuff!! I applaud you for doing this,
and being so systematic about it.
Over the past couple of years I have made a (much less concerted)
effort to find flight spots in Contra Costa's interior coast range and
have not been very successful.
I am most intrigued by your first location--"Highland ridge--gate
saddle" for a couple of reasons, one is that you seemed to have a
fairly noticeable flight here of birds moving exclusively north, and
secondly is that it shares similar topography to a site that I have
been eyeballing for a while now but have never actually checked myself
at the intersection of Sycamore Creek Rd. and Meridian Ridge Rd.
(37.848424, -121.914870). Both places are lower saddles in the higher
elevation, southern sort of ridgeline that marks the southern end of
Contra Costa's bit of the Diablo Range. I would have checked the spot
I shared above in previous years if it weren't about 3 miles from the
closest public parking that is accessible pre-dawn. Unless, of course,
you know someone that lives behind the gates in Blackhawk (I don't) in
which case it is only about a mile's hike to this site.
I have also had minor flights along Blackhawk Ridge accessed from
Finley Road, but this is a grueling hike and doesn't seem
exceptionally productive. I have also had some movement by where Green
Ranch Rd. meets Summit Rd. well within the park. The only downside to
this site is that it is difficult to get to pre-sunrise, because the
park gates open only around 7am or up to an hour later, and it is a
half an hour drive from the park gates to that spot. So I have never
pursued that further. I also remember one morning standing around at
Morgan Territory in that big meadow where the Volvon Trail starts and
having some birds pass north very high overhead. This has led me to
wonder whether on the south end of the park, east of Morgan Territory
Rd. there might be some spots where those birds pass relatively low to
the ground as they gain elevation.
And that is all that I have to say. Good luck, Michael, and please
keep us updated on what you discover during this process!! This is
On Tue, Apr 12, 2022 at 9:50 AM M via groups.io
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Thanks Ethan! That’s interesting to hear about the flyovers around the Volvon Trail at Morgan Territory. I want to get back out there, but who knows how far of a hike would be needed to get to a better spot. It certainly seems really tricky to find sites that have good topography, wind, and accessibility. I’ll post whatever I’m able to find!
On Apr 13, 2022, at 6:21 PM, Ethan Monk <z.querula@...> wrote:
And for those interested in seeing the migration patterns in their county the night before you go birdwatching, check out BirdCast: