Date of this Version
High voltage powerlines form a spider-web pattern across North Dakota as they radiate outward from electric generating sources at Garrison Dam and nearby lignite-fired power plants. In 1976 there were approximately 1100 miles of high voltage powerline in the state, which required approximately 4500 large steel or aluminum towers for support (G. R. Anderson, personal communication). Moreover, officials of power cooperatives and privately-owned utilities anticipate the construction of over 900 additional miles of high voltage lines by 1981. As North Dakota coal resources are developed the powerline network will probably continue to grow.
Our interest in powerlines was stimulated several years ago when we learned that raptors were nesting on towers supporting high-voltage lines maintained by the US Bureau of Reclamation (USBR). To learn more about the use of towers by raptors we requested in 1973 that USBR personnel report all raptors and nests they observed on these structures during routine aerial inspections. In the spring of 1976 we were able to monitor closely a number of raptor nests built on powerline towers throughout North Dakota. Our objectives were to: (1) identify the raptor species using tower sites for nesting, (2) estimate the frequency of nest occurrence along selected powerlines, (3) report the success and productivity of these nests during the 1976 season, and (4) compare the productivity of nests constructed on towers to nests in non-tower sites.