Re: Swainson's Group 6
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Migration counting at Bear Divide started on Thursday morning and the totals are visible in eBird. Nobody saw Swainson's hawk there this morning or yesterday morning. Note that those counts often end by 11 am, so if the big pulse of hawks seen in Altadena at 4 pm passed through Bear Divide yesterday, there weren't any birders there to observe them (I checked eBird: there weren't any reports in late afternoon).
I received a couple of private emails from observers in Monrovia that dedicated watches there this morning did not turn up any Swainson's hawks, so apparently the lack of large flocks over Altadena was not a fluke. It really looks like the birds either moved over the mountains between Glendora and Monrovia, far enough south that observers in Monrovia, Eaton Canyon, and Altadena were not able to see them, or perhaps to high elevations where they would be very difficult to spot.
Part of our interest in extending a picket line to the north was to understand the extent to which the hawks move through the San Gabriel Mountains. On March 27, 2018 David Coates reported a flock of about 100 above the Chilao campgrounds. This year, most of the roads are still closed due to snow and rockslides so we weren't able to place any observers up there. Perhaps next year.
Weather could also play a role: today conditions have been very different from yesterday, when there was a low overcast for most of the day over the foothills. Swainson's hawks often fly below the clouds and that can make them easier to see. On a day like today, there weren't any low clouds in the morning so perhaps the birds were flying higher.
On the general topic of weather, Luke and Kimball gently reminded me to ask everyone who reports Swainson's hawks to note weather conditions in their eBird lists: wind direction, speed if you can (say, using the Beaufort Scale or mph), temperature, rain/drizzle, percentage of cloud cover, and if clouds are present, the elevation of the cloud bottoms. Yesterday, for example the clouds above Altadena were down to about 3000-3200 feet around 4 pm, which I calibrated against areas I could see where I've been hiking.
Thank you, and keep looking up!
From: "Mike Peralez"
To: "Lance Benner"
Sent: Friday March 17 2023 1:56:33PM
Subject: Re: [LACoBirds] Swainson's Group 6
Y. Lee saw hawks moving heading north from Easton canyon area....??
This morning's Glendora hawks all moved W or WNW. None appeared to go north up the San Gabriel Canyon.
Perhaps Bear Divide might prove interesting.
On Fri, Mar 17, 2023, 11:42 AM Lance Benner <lbenner@...> wrote: