Bird of the Week

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    Photo courtesy Keith Bruno

    This week’s Bird of the Week, compliments of the Weminuche Audubon Society and Audubon Rockies, is the prairie falcon.

    Though many folks are perhaps more familiar with the storied plight (associated with pesticides and especially DDT) and recovery of the famed peregrine falcon (migratory here in southwest Colorado), the prairie falcon, a semi-year-round resident to Pagosa Country, is also an awe-inspiring hunter and aerialist. This species, believed to have diverged from ancestors of the peregrine lineage some 3 million to 5 million years ago, has evolved into a more arid lands-adapted falcon. These birds are very comparable in wingspan (40 inches), but typically maintain lesser weights (1-2 pounds) to their darker colored cousins (2-3 pounds), as their diet and lifestyle in the desert west often warrants more work for fewer calories. 

    As with most raptors, the females are larger on average and can boast a beak-to-tail length of 17-18 inches. As far as plumage goes, these birds are browner overall, especially when viewed from above. Under the wing, these birds have an alternate white and brown pattern with distinctly darker “wingpits.” Males and females alike don a definitive brown malar stripe or “mustache” and white eyeline above the brow. As birds mature, their breasts become less white (more darkly streaked with brown) and the skin at the base of their beak and on their legs becomes noticeably more yellow.

    During the summer, these birds will largely subsist on ground squirrels and supplement with lizards and insects in open country such as shrublands, grasslands and even alpine tundra (diet shift to pikas). Come winter, these birds shift to preying on rangeland birds such as horned larks and western meadowlarks.

    Hunting styles often mimic the lower elevation stalk-and-attack flight methods of their smaller cousins, merlins. Though fast like peregrines, these birds operate with more sustained cruising speeds (45 mph). They don’t tend to dive from high elevations in 200-plus mph efforts like peregrines do. In flight, prairie falcons can certainly appear almost torpedo-like in their pursuits. Their wing shape has the iconic narrow profile of all falcons, beats are typically stiff and resolute and the tail is noticeably longer proportionally compared to peregrines. An interesting adaptation, this species has cone-shaped projections in the center of their nostrils which slow down air flow at high speeds, protecting the lungs from damage.

    Recognized as more or less stable in population numbers, this species suffers when large-scale agriculture offsets good ground squirrel habitat with heavy irrigation. Nesting disturbance during the breeding season and recurrent wildfire offer challenges, as well. A group participating in the Christmas Bird Count recently was thrilled to witness the eccentricities of prairie falcon hunting on count day.

    For information on events, visit www.weminucheaudubon.org and www.facebook.com/weminucheaudubon/.