Regarding the Dec. 7 article “Permits for wind farms that accidentally kill eagles extended”:
As wind farms expand across the country in lands occupied by eagles, bird mortality becomes of interest to citizens. The effects of bird mortality upon eagles by commercial wind farms have been investigated in the past and shed much light upon the subject.
Two major studies were conducted in the Altamont Pass, Tehachapi Pass, and the San Gorgonio Pass located in the wind resource areas of California. It was found that the entire habitat suitable for breeding was occupied by territorial eagle pairs. Suitable breeding areas will have sufficient food supplies to support breeding of families. For other sub-adults and adults without breeding territories, these eagles must wait for a vacancy of a territorial owner. These other sub- adults and adults occupy territory outside of the suitable breeding area.
A state of equilibrium develops between the breeding areas and the outlying areas. The tendency exists to replenish those lost by wind turbines in the breeding areas by adults in the outlying non-breeding areas. Thus, the non-breeding adults in the outlying areas replace the breeders that have died in the breeding areas where the wind turbines exist. For areas with large populations, equilibrium is established between the breeding and non-breeding areas. It is important to understand behavior of eagles and the environment upon which eagles live so as to understand that commercial interests are not always detrimental to the eagles population.
Gary C. Young
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