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Here’s another in a series of images of youngsters. Today’s subject is a nestling Swainson’s Hawk. I found this youngster one morning a couple of weeks ago peering out from its parents’ nest in a mesquite tree along a rural road. Look closely at the lower right side of the image and you’ll see a bit of the downy shape of at least one other nestling bird.
Swainson’s Hawks are closely related to Red-tailed Hawks. In southern Arizona their breeding cycle is considerably later than that of the Red Tails and that may have something to do with these birds’ migration pattern. Some Red Tails migrate but many are year-round residents. Those that do migrate tend to make relatively short journeys each autumn and winter. The Red Tails feed mainly on a diet of rodents such as ground squirrels, and these animals are active in our area most of the year, providing a steady and relatively reliable diet for the Red Tails. Because they will have rodents available as food, Red-tailed Hawks breed early in the season — sometimes as early as late February or early March — and their offspring are fledged by late April. They have all summer to learn how to hunt their rodent prey.
By contrast, Swainson’s Hawks make extremely long migrations. Each autumn they migrate from their summer homes all the way to Argentina, a one-way journey of thousands of miles. They make the return trip each spring. In order to be able to make the trip these hawks need an abundant supply of high energy food. In the summer months they’ll eat rodents even as Red-tailed Hawks do. But, in late summer and early autumn Swainson’s Hawks fatten up by eating grasshoppers. It’s not unusual in mid-September to see hundreds of these hawks foraging on the ground in a large field, gobbling grasshoppers as fast as they can seize them. These hawks time their breeding season so that the youngsters are fledged and able to fly long distances in late summer. That’s about the time of year when grasshoppers are at their peak numbers. The youngsters join the adults in fattening up on grasshoppers. The nestling in this photograph will be fully fledged by now, and will spend the next six weeks or so, learning how to forage. By early September, if it learns its lessons well, it will be ready to make the annual migration.
Image made with a Canon 5Div, 400mm f4 DO II lens+1.4x telextender, M setting (auto ISO), ISO 1000, f5.6 @ !/2000, exposure compensation +1/3.
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