Curious Nature: Fight of the fast fliers
Vail, CO Colorado
When human populations are confronted with ecological problems, one common response is that these problems are too large to really be addressed or solved. Much of this sentiment is accepted because of the way problems are presented. Good reminders that human decisions can make a difference in ecology and biodiversity shouldn’t be overlooked. One of the best examples of this type of positive behavior is the situation of the peregrine falcon’s past plight here in the United States.
Peregrine falcons (Falco peregrinus) are one of the most resilient bird species we know about. This species can be found on every continent except Antarctica. They are superb survivors thanks to their savvy hunting skills and lack of predators. These two-pound birds with three-foot wingspans are incredibly apt hunters who catch their prey in mid-air. With brown backs and buffed, striped chests topped off with a striking striped face, these birds personify beauty and grace as they soar through the air. Normal flight speeds of the peregrine are 40-50 mph, but they have been clocked as fast as 200 mph in a stoop, or dive, as they chase down their prey. They then lock their talons around birds, or the occasional bat, they capture when hunting, carrying their quarry to a high perch to finish it off. Peregrines often hunt in pairs, where their hunting partner is often their life-partner, since peregrines are monogamous and mate for life. This ensemble of finely honed adaptations has contributed to the success of the peregrine falcon populations worldwide.
But things weren’t always so wonderful for our falcon friends. Even with all of these capabilities and adaptations, peregrines were being threatened and were on the brink of extinction in the 1970s. The culprit was an oft-used insecticide DDT, known to chemists as dichlorodiphenyltrichloroethane. It was an exceptionally effective man-made insecticide that was first discovered in the 1870s, but not used commercially as an insecticide until after World War II. DDT is a hydrophobic chemical, meaning that it doesn’t easily break down in water, but it breaks down easily in fats, oils or lipids, making it lipophilic. This lipophilicity meant that organisms lower in the food chain would absorb DDT, which would then accumulate in organisms higher up the food chain in a process known as bioaccumulation. Since peregrine falcons were atop their food chain, they were consuming concentrated amounts of the chemical. The effects of the DDT on the peregrine falcon weren’t clear at first, because they weren’t being killed directly by the DDT, but the side effects became obvious over time. DDT limited calcium production in many birds, including the peregrine, which would weaken the egg shell strength, causing eggs to break during incubation. By the 1970s, successful reproduction nearly came to an end. A study in 1975 showed only 324 mating pairs in the United States, about 90 percent lower than historical levels. Colorado was down to only five nesting pairs.
Once the problem of raptor reproduction (other raptors were impacted, including the bald eagle) and its source became apparent, DDT was banned from agricultural use in the U.S. in 1972. The detrimental effects of the chemical were decided to be too great, and this decision, which had gained public attention and outcry, saved several birds of prey from continued population decrease and possible extinction.
This environmental success story stands as a testament to the resiliency of species and to the power of human potential to enact positive change. While not every environmental issue has such a singular cause, attempts to more clearly understand environmental problems and their causes can make a vast difference in the world that we leave to future generations. The 50 to 100 pairs of peregrine falcons that now call Colorado home would probably agree with this.
Travis Long is a graduate fellow educator at Walking Mountains. While he is saddened by the rate of melt of the snowpack, he is excited for the quickly approaching spring and the birds that will come with it.