Bird of the Month: Swainson’s Hawk (Buteo swainsoni)

Swainson’s Hawk is one of those birds that can catch your attention when hundreds fill the sky overhead, mixed with migrating Redtail Hawks and an occasional Golden Eagle

April and October are the two months of the year when bird migration can be a spectacle for those that notice the movements of birds. Swainson’s Hawk is one of those birds that can catch your attention when hundreds fill the sky overhead, mixed with migrating Redtail Hawks and an occasional Golden Eagle. My favorite places to catch the migration of these hawks is in the agricultural areas west of Phoenix, and in the fall, the agriculture areas in southeastern Arizona and southwestern New Mexico. Swainson’s Hawks will be standing on the ground or following the tractors hunting for grasshoppers and small rodents. The irrigation center pivot booms are perfect perches for a hunting vantage point.  I have seen over a dozen birds perched on one boom as it slowly moves in a circle around the field. 

 A smaller and slimmer hawk than the more common Redtail Hawk, both of which are in the buteo group of hawks, the Swainson’s Hawk is a bird of the American west. When soaring the wings are held above the horizontal and the wings look pointed. I find the reason for the look of a pointed wing to be a cool fact. Unlike other buteo hawks, the Swainson’s has a longer third primary feather. I think the lighter color phase is a most elegant bird, with a dark head and chest, whitish body and a two-toned underwing with a striking dark trailing edge. The dark phase is trickier to identify and can be confused with a juvenile Redtail Hawk. The best field marks for the darker birds is the pointed  shape and the dihedral set of the wings and an almost teetering flight like a Northern Harrier. 

Buteos are specialists in hunting small mammals, and the Swainson’s Hawk is no exception. What does make them different is the number of insects in the diet. Grasshoppers, dragonflies, and crickets are the primary food when not feeding chicks. They can catch insects on the wing and even hover like a kite. 

Swainson’s Hawks are primarily a bird of the western grasslands, often in association with sagebrush and pinyon/juniper. The majority nest in the Central Great Plains and the Great Basin. Nests are built in available trees often in adjacent riparian areas or in junipers. A portion of the population finds breeding sites in the southwestern grasslands of Arizona, New Mexico, and west Texas. My best observation of a breeding pair was last year on my Breeding Bird Survey route near Seligman, Arizona. I spotted a bird in a juniper tree by the road, When I stopped I realized it was two birds, and they were quite occupied “doing it” (copulating). I was very safe in recording them as “breeding” birds on my survey! 

The Swainson’s Hawk migration through Central America is an amazing spectacle, a true “River of Raptors”. Tens of thousands of birds funnel through Panama and southern Mexico heading north to their breeding grounds in the western United Stets and Canada and again in the fall heading to the wintering grounds in the Pampas grasslands of Argentina. Audubon Migration Explorer shows this amazing migration in time lapse. 

A good number of Swainson’s Hawks have been tagged with telemetry transmitters, giving avian scientists added insights to the migration journey. Audubon has featured the journey of Diego. He was captured and tagged in 2018 at Salt Lake City airport during his spring migration. He nested in Idaho and then headed south in August, joining other Swainson’s Hawks feeding on grasshoppers in the Texas grasslands and was part of the Vera Cruz, Mexico River of Raptors spectacle in October. Columbia was an important stop over, where Diego rested before continuing to Argentina, arriving in mid-November. He returned to Idaho the following spring, as a seasoned traveler! 

I visited the Buckeye, Arizona area in early April and was treated to a half dozen Swainson’s Hawks soaring over a farm field. So, keep your eyes open and look toward the sky for this very handsome hawk!

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