Resources & Research : Animal & Plant of the Month

Art Elser

Animal of the Month
Swainson Hawk

The Swainson's hawk, Buteo swainsoni , is a large raptor about the size of the red-tailed hawk. It is 21 inches long and has a wing span of 52 inches. These hawks are warm-weather visitors to PCC, with the first migrants appearing in early spring and leaving in mid fall.

Perhaps I should have capitalized migrants because these amazing creatures make round trips to Argentina on their annual migrations, over 6,000 miles. The pampas of Argentina are similar to the plains of North America, so these hawks feel at home here. They migrate in flocks of hundreds, sometimes thousands, using thermals to gain altitude, followed by long glides.

Swainson's and red-tailed hawks compete for food and nest sites here at PCC. This April, while near lone tree, we watched pairs of both species vying for the existing nest in that tree. Perhaps the competition was too much for both pairs since neither seems to have claimed the nest.

During breeding season the Swainson's diet consists of mice, voles, ground squirrels, rabbits, birds, and reptiles. During the rest of the year, this hawk feeds on insects like grasshoppers, locusts, and beetles, thus one of its common names is grasshopper hawk. Its normal diet of insects leads to its long migration away from our winter to a place where insects are plentiful.

Because Swainson's hawks often hunt from low perches or from the ground, look for them low, on fence posts or gates. They will, however soar like red-tails, so don't exclude looking up for them. The dark trailing edge of the wings of a Swainson's easily distinguish it from the red-tail. The Swainson's wings are also more pointed than the red-tail's. And when perched, the rusty-colored bib identifies the hawk is a Swainson's.

Plant of the Month

willow along Tollgate Creek, winter 2008 JPMoyer

Plant of the month, May 2008
Bluestem Willow
Salix irrorata

Look for:

•  A shrub up to 12 feet in height growing along steams

•  Dark straight stems covered with a bluish coating

•  Catkins, or flowers, that push out in early spring

•  Catkins that are hairy or smooth (depending on whether they are male or female) about ¾ inch in length

Ecology and Human Uses:

•  The catkins often are found before the leaves open, early in the spring

•  Very common on the eastern slope of Colorado , our best native pussy willow

•  Willows are dioecious, male and female flowers or catkins on different plants

•  The male flowers are without corolla or calyx but merely a bunch of stamens (see image)

•  Almost all willows take root readily from cuttings or where broken branches lie on the ground

•  Willows are used as food plants by the larvae of some Lepidoptera species (moths and butterfiles)

•  Native Americans relied on the willow as a staple treatment for a wide variety of ailments because it contains salicylic acid, the precursor to aspirin

•  Other uses include wood for brooms, cradle boards, dolls and toys, sweat lodges and basket weaving

•  These large native plants provide good slope stabilization and thus soil erosion control

•  The willow is mentioned in literature by Hans Christian Andersen ( Under the Willow Tree ) and more recently by JK Rowling in her Harry Potter series (the ancient tree on the school grounds of Hogwarts called the Whomping Willow)