Posted by: barn owl | February 29, 2008

Whooping Cranes and Wind Farms

Wind farms, which currently generate about one percent of the energy in the US, would seem to be an excellent sustainable fuel supply. I often see trucks carrying the huge blades, turbines, and towers to new wind farms in West Texas and Southern Colorado, where the strong winds that once were just an accursed nuisance now provide a much-needed boost to the rural economy. However, wind turbines, and the associated power transmission towers, may pose a threat to migratory birds, including the endangered Whooping Crane (Grus americana).

migrate

Migration corridor for the Wood Buffalo-Aransas Whooping Crane population
Source: Texas Parks and Wildlife Department

Conservation efforts, both publicly and privately funded, have increased the Whooping Crane population from a mere 15 birds in 1941, to the current total of 266 individuals. The most robust group is the Wood Buffalo-Aransas population, which migrates each year between breeding grounds in Canada, and the winter haven at Aransas Pass National Wildlife Refuge near Rockport, on the Texas coast. Whooping Cranes, which numbered between 800 and 1300 individuals in 1869 (Cannon, 1996), were decimated by habitat loss and hunting. These large birds require marsh and wet prairie habitat, in which to forage for fish, insects, small tetrapod vertebrates, crustaceans, berries, and grain. The Migratory Bird Treaty of 1916 banned hunting of the birds for a period of ten years, but the crucial conservation measure came in the 1930s, with the purchase of the winter feeding grounds on the Blackjack Peninsula in Aransas Bay (Cannon, 1996).

cranes

Whooping Cranes, Grus americana
Photo: © Texas Parks and Wildlife Department

Both the wind turbines and the power transmission lines can be deadly for many species of birds, but migrating cranes (both Sandhill (Grus canadensis) and Whooping Cranes) and waterfowl seem to be especially vulnerable. Since collision with power transmission lines is the most common cause of death for both the introduced, or foster, Rocky Mountain and the Wood Buffalo-Aransas populations of Whooping Cranes, Brown and Drewien (1995) monitored the effects of two types of power line markers (yellow spiral vibration dampers or yellow fiberglass swinging plates) on reducing wild bird mortality from collisions, in the San Luis Valley of Colorado. These researchers found that such markers were effective in increasing visibility of power lines under a variety of conditions and seasons, and numerous species of birds adjusted their flight patterns accordingly, to avoid collisions. Wind turbines pose a different challenge for increasing visibility, but the power transmission lines from wind farms should certainly be marked to reduce their impact on migratory bird populations.

References:

Brown, W.M., and Drewien, R.C. (1995). Evaluation of two power line markers to reduce crane and waterfowl collision mortality. Wildlife Society Bulletin 23(2), 217-227.

Cannon, J.R. (1996). Whooping Crane recovery: a case study in public and private cooperation in the conservation of endangered species. Conservation Biology 10(3), 813-821.

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