Date: 9/8/26 7:41 pm From: <aiantony...> Subject: [cobirds] Spectacular record-breaking migration of Swainson's Hawk today at the Mount Zion Hawk Watch
This morning we had a spectacular migration of 57 Swainson's Hawk in 25 minutes between 9:33 a.m. and 9:58 a.m. DST at the Mount Zion Hawk Watch!
For details look at my report for the day from Mount Zion on COBirds or Hawkcount.org.
To put things in perspective, last fall when Liza and I conducted an exploratory count at Dinosaur Ridge Hawk Watch we were thrilled to see a total of 68 SW for the entire season, with 14 SW on August 19, 2025 on our first day of counting, compared to the 36 SW we saw for the abbreviated season at this site in fall 2024.
Since there are no other fall hawk watches in Colorado, I compared it with spring numbers of SW at Dinosaur Ridge on hawkcount.org.
In the 15 years before Emma Riley became the official hawk watcher, counting by volunteers yielded between 2 and 17 SW a season, while for the 5 years between 2022 and 2026 in spring during the ‘Emma era’ the counts of SW were 54, 77, 48, 46, and 57 respectively for the entire spring seasons, with 14 being the maximum counted in a single day in 2023.
When we started this fall season at Mount Zion on August 1, we started counting at 10:00 a.m. DST as that was the time Dinosaur Ridge started in spring. My intuition told me that hawks may be migrating earlier so we switched to 9:00 a.m.. If we had started at 10:00 a.m. today we would have missed the entire SW migration today!
I guess we were lucky, but skill, diligence, and dedication all played a part
I told Zak Hepler at the watch last week, we had a truism in New York that the more times you come to a hawk watch, the greater are your chances of seeing a rarity or a spectacular event, such as today.
This is the right time of the year for the fall SW migration along the Front Range, the next week could be the peak migration period.
Since SW is primarily a plains breeder in Colorado, Wyoming and Montana, these SW migrate South in fall, and North in Spring along a broad front using thermals, not needing thermals.
On April 23, 2019 Dinosaur Ridge counted 7 SW all day, while on the same day Liza had gone on a DFO trip with David Suddjian to Weld County and in one field had 72 SW!
If you look at the range map of SW on the Merlin app or elsewhere, it also breeds all the way North from Alaska, Western Canadian provinces of the Yukon, Northern Territories, Alberta and British Columbia, South to the US. These SW migrate along the Rocky Mountains.
Many of the hawk watches in the West along the Rocky Mountain Flyway seem to be along the eastern edge of the Rockies or just within the foothills. (You can look up hawkcount.org for that, clicking on Find a Hawk Watch in the left sidebar, clicking on individual states along the Rocky Mountains). There are good reasons for that. Thermals are more consistent along the eastern edge, also providing ridge/orographic lift, as well as providing food along the grasslands compared to lack of visible prey over the heavily treed high peaks of the Rockies. The high Rockies can be treacherous for migrating raptors because of severe turbulence with wind shear and downdrafts that can dash a raptor to its death, and the freezing air over the high peaks prevents the formation of strong consistent thermals. Also the Front Range is a stark unmistakable visual landmark for migrating raptors, keeping the Rockies to their right/west they have an infallible geographic landmark to migrate along.
Liza and I together with Zak Hepler are leading a DFO/ Audubon field trip to the Mount Zion Hawk Watch on Saturday September 12th, which has openings. If you're interested, and you don't have to be a member of DFO to go on the trip, go to DFObirds.org to sign up for it. The scenery from the watch is spectacular.
Ajit I. Antony
Central Park, Denver, Colorado
Former volunteer counter at Mount Peter, Hook Mountain, I-84 Overlook Hawk Watches in New York from c.1995 until we moved to Denver in 2022.
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