On some cool early morning in the coming weeks, the chestnut-colored bibbed raptor you see here in my photo will lift off its north metro perch and begin a two-month, 3,000-mile voyage to its wintering grounds in the fertile low grasslands of Argentina and Uruguay. Along the way it will stop for foraging, resting, and waiting out harsh weather conditions. It'll also meet up with anywhere from 300,000 to a half million or more of its cousins who are doing the same resettling.
Swainson's Hawks, who's eponymous common name should be changed to reflect their grasslands habitat, that is, Pampas Hawks, are buteos of open spaces and each year they migrate to and from the plains of North America to the plains of Argentina. That's 12,000 miles and four months of flying for each year they're alive. And during those epic migrations they subsist primarily on eating grasshoppers, crickets, and such that they catch on the ground and in the air. Insects are also their primary food base during their stays at their winter destinations. Based on analysis of their cast-off pellets, each Pampas Hawk consumes around 100 grasshoppers a day. Multiply that by the total number of these long-distance migrators and the aggregate number of grasshoppers, etc., consumed by all of them during their annual migrations and wintering is…just astounding.
During their breeding season in our mid-western and western grasslands, though, they're not running down little grasshoppers and other insects on the ground or in the air to bring to their babies. Of efficiency and nutritional demands, they modify their foraging to include warm-blooded mammals and cold-blooded reptiles to meet the dietary needs of the females and their voracious and rapidly growing young.
Overall, these buteos are about the same size as Red-tailed Hawks, which are large hawks, but they do have a bit longer wingspan than the red tails.
Hope everyone gets a chance to observe a Pampas Hawk or two before they leave!
Cheers, and good birding to all!
Walter "Ski" Szymanski
