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Hawkwatch Comes to Borrego Springs

By Hal Cohen ( 2003)

(Join Biologist Hal Cohen in Borrego Springs each spring as the annual hawkwatch gets under way. Check our website for updates.)

This article was originally published in The Sand Paper, the membership newsletter of the Anza-Borrego Desert Natural History Association

borrego springs hawk watch swainson's hawk

Thirty-six turkey vultures put down in the eucalyptus trees directly across from my home on February 28, 2003, at 5:30 p.m.  Little did I know that this day would be the beginning of hawkwatching in Borrego Springs, a desert community surrounded by mountains in Southern California, just 80 miles north of Mexico.

The rustling of wings flapping and branches bending was soothing. The vultures settled in for the night. I thought of my move to Borrego a year ago, leaving the Midwest where I counted hawks seriously for many years. I said goodbye to Concordia University on Lake Michigan near Milwaukee, a merlin mainline.  No longer would I watch clouds of broadwings at Erie Metro near Detroit or Bald Eagles on the Mississippi. Whitefish Point, Illinois Beach, and Indiana Dunes would be memories. I said goodbye to Mount Hoy just 30 miles west of Chicago, a place without leading lines to funnel hawks. Mt Hoy was my first hawkwatch. It's here that I honed my skills in hawkwatching. How I yearned for the hours of watching, digging in and looking at puffy clouds, hoping for a few hawks to stream by.


The next morning I followed the birds as they lifted, circled and streamed north then west to avoid the imposing height of Toro Peak at 8700 feet. Coyote Canyon provided an exit from Borrego Valley. The canyon cuts between the San Ysidro Mountains to the west and the Santa Rosa Range dominated by Toro Peak to the north. This access route allows the birds to continue their journey north.

During the first two weeks in March I concentrated my efforts on locating a site to watch the migration of vultures. At this point I was satisfied working with turkey vultures. On March 9th I counted an unknown raptor from a great distance. It looked buteo-like but was slimmer than a redtail. The bird did not register quite right. Later I realized that this was perhaps my first of many Swainson's hawks to move through the valley. 
swainson's hawk and moon borrego springs Ray Spence photo

Swainson's Hawk and Moon - photo by Ray Spence

I located the watch at the junction of Henderson Canyon and Borrego Springs Road.

I returned to the watch site March 2, temperature 83 degrees, 10% clouds, wind ESE 5 mph, humidity 21% visibility unlimited. At 8:11AM 25 Swainson's kettled up and flew directly overhead and across the ridge. At 8:14 a.m., 8 Swainson’s followed the same route. Birds continued to stream overhead until 8:50 a.m. the totals in less than an hour were 63 Swainson's and 2 turkey vultures.

On March 11, I left the watch at 9 a..m. and headed home. As I turned south on DiGiorgio Road I spied a kettle (a large group of hawks swirling around presenting the shape of a kettle) of what appeared to be ravens. I stopped my truck and swung my binocs up to reveal a kettle of 16 Swainson's hawks. They began to stream north and then west through Coyote Canyon.

Immediately I scanned back to the area where the first kettle formed. Another kettle began to rise from the same area. I counted 17 Swainson's in this second group. They followed the same path out of the valley. For the next week only 10 more Swainson's were observed. On March 18th I left for a week in Mexico, returning March 25th.

On April 5th I decided to relocate the watch to DiGiorgio Road to intercept birds directly in their feeding and roosting area. Many birds were on the ground and in the tamarisks. Kettles began to form at 8 a.m.  Totals in three hours of observation were 5 tv's and 105 Swainson's.  It was apparent that hawks most be coming into the valley in the evening so I returned to DiGiorgio Road at 5:30 p.m. and found 22 birds close to the ground but flying. As darkness approached, I slowly drove DiGiorgio Road home.

I noticed a huge kettle of birds to the southeast as I drove. Stopping next to the road, I quickly focused on what was the biggest kettle of Swainson's I had ever seen. “Tornado! by gosh a tornado of hawks!” I shouted with no one nearby to hear. The hawks ranged from ground level to heights of at least 1,000 feet. A car pulled up and two young watchers emerged. They had never seen a Swainson's Hawk in their life (lives?) and now we were witnessing hundreds. It was rapidly becoming dark as the birds began to descend.  I counted in tens then 50's as the birds streamed north. “Gads!” I shouted, "they are splitting up."  In fact, the majority of birds continued north and a splinter group flew west, directly over us. I followed the larger part of the group north as they began to descend toward Coyote Canyon. By 6:30 p.m. it was too dark to follow the birds. I estimated around 700 to1,000 were in the kettle.
On April 6 we counted only 210 Swainson's. The remainder had made it through. Coyote Canyon the prior evening. We were now convinced that the birds were coming into the valley in the evening, roosting and feeding on the caterpillars in the morning. The large group that came in April 5th split with the majority gliding into Coyote Canyon to feed further north.

On April 7 over 100 hawks were on the ground this morning, suggesting that again we missed a movement the prior evening. We were now determined to witness migration into the valley.

kettle of swainson's hawks borrego springs

First kettle of the day

A total of 185 Swainson's departed today. We returned in the evening and spotted 21 hawks descending into the area.  Another 30 were already on the ground or in the trees.   Migration continued daily with totals for the period April 8-19 of 267. The grand total for the season included 2031 Swainson's Hawks, 310 Turkey Vultures, 1 Osprey, 2 Northern Harriers, 1 Redtail, 1 Ferruginous Hawk, and 1 Golden Eagle. We spent 74 hours at the watch. Our average hourly total was 31.7 hawks.

Swainson's Hawks are endangered in California. They migrate from the pampas of Argentina to as far north as Alaska. The central valley of California still has a few nesting birds. The work we have begun on Swainson's Hawks may help determine if a viable population is increasing. Next spring we will try to retrieve feathers to be used in genetic studies, linking our sightings with nesting Swainson's further north.

2004 hopefully will bring the hawks back to the valley. Many questions still remain unanswered. We now know, however, that Southern California has a new hawkwatch.

Join Biologist Hal Cohen each Spring in Borrego Springs as the annual Swainson's Hawk Watch gets underway.

Check our website for up dates in late January or February.

© Anza-Borrego Desert Natural History Association, 2003, from “The Sand Paper” newsletter, Volume XXXII, Issue 2.