Swainson’s hawks are about the same size as red-tailed hawks. They are generally a bit lighter than the red-tailed hawks, but have larger wingspans. When they are soaring overhead, look for the narrower wings and banded tail.
Swainson’s Hawks in this ecosystem
In the winter, Swainson’s hawks from here to Canada gather in huge flocks (a group of migrating hawks is called a “kettle”) that can number into the tens of thousands. Other species, including turkey vultures, will join them at the beginning of their long migration. The vultures will drop out in Mexico as the Swainson’s hawks continue their two-month, 6,000-mile journey to Argentina for the winter.
Since they spend time in so many different ecosystems, their protection under the Migratory Bird Treaty Act is critical, as are cooperative efforts that span states, nations, and even continents. In the 1990s, there was a mass die-off of Swainson’s hawks in Argentina, with over 5,000 dead in just one summer. About 4,000 of those deaths were attributed to monocrotophos, an insecticide that was removed from in the U.S., but was still used heavily in Argentina. Distribution of monocrotophos was stopped in Argentina, and Swainson’s hawk population numbers stabilized. This is just one example of how actions in a different ecosystem on a different continent can affect our animals here in the greater Yellowstone ecosystem.
During nesting season, Swainson’s hawk diets consist of the classic “three R’s” of raptor food: rodents, rabbits, and reptiles. When migrating, they switch to a diet of almost exclusively insects, especially grasshoppers, which gives them their nickname of “grasshopper hawk.”
At the Sanctuary, we feed a variety of small animals, principally rodents.
BEHAVIOR & Lifespan
They sometimes hunt on the ground, running after their prey.
In the wild, Swainson’s hawks have a life expectancy of 16-19 years; in captivity they can live over 24 years.