Bald Eagles (Haliaeetus leucocephalus) have been known to nest rarely on human-made structures (Postupalsky 1978 in S.A. Temple [Ed.], Endangered birds: management techniques for preserving threatened species, Univ. of Wisconsin Press, Madison, WI U.S.A.; Grubb 1983, Raptor Res. 17:114–121). In the spring of 2005 a pair of Bald Eagles nested successfully on a 1.4 × 1.4 m nest platform atop a 27 m utility pole constructed in 2001. It was one of two extraordinarily tall poles erected on Reliant Resources electrical power station along the Delaware River at Portland, Pennsylvania. This was a mitigation measure designed to benefit nesting Ospreys (Pandion haliaetus). The power company planned to build several gas turbines in close proximity to a well-established nest pole occupied since 1986. The 440 ha coal-fired power station was chosen in 1982 as a secure Osprey hacking study area. Subsequently, the region around the power plant became home to one of the first hacked Osprey populations, and more than 120 young were fledged there from 1986–2005 (Rymon 1989, in R.D. Chancellor [Ed.], Raptors in the modern world, World Working Group on Birds of Prey and Owls, Berlin, Germany).
The purpose for erecting such tall poles was to exceed the height of the surrounding tree canopy and the previously constructed 15 m nest poles located near the disturbance area. A pair of Ospreys occupied one 27 m nest platform during 2002–04, and fledged an average of two young/yr. During the winters of 2003–04 and 2004–05, a pair of Bald Eagles was observed perching on the same high nest platform. They also utilized it as a night roost during periods when they were foraging locally. Stick carrying, courtship behavior, and nest reconstruction were noted in February of 2005. Incubation began in early March. We observed two eaglets approximately 2 wk old on the nest on 21 April 2005. During the period leading up to fledging, eaglet activity leveled the small nest and by 17 June just a few original sticks, nailed there to attract Osprey, remained (Fig. 1). The nestlings fledged between 17 and 19 June and returned to the platform for a 2 wk period, during which they were provisioned by the adults. They remained on or near the platform until 16 July when they and the adults began to forage along the Delaware River. Very little territorial aggression between resident Ospreys and Bald Eagles was observed. The Ospreys merely relocated to a nest platform on one of the 15 m nest poles.
The adult Bald Eagles were not banded, but might have been the same pair that nested 2.5 km downstream from the tall nest pole during the 2004 breeding season. That nest was built on an abandoned raptor nest approximately 23 m aboveground in a tulip poplar (Liriodendron tulipifera) on a forested slope above the Delaware River, and was unoccupied in 2005. The next-nearest Bald Eagle nest was approximately 20 km away.
Ospreys have habituated well to human activity near the power station, as evidenced by their nesting on the very tall pole only 200 m from a coal delivery train track and parallel highway. Bald Eagles nesting in such a location was considered to be an unlikely event. However, the number of wintering and breeding Bald Eagles have increased in Pennsylvania, as elsewhere. Since 1968, when only one or two wintering eagles were recorded along the Delaware River (Rymon unpubl. data), the population there has increased to over 200 wintering birds, many of which are also year-round residents (Pennsylvania Game Commission unpubl. data; Nye 1989, in B.G. Pendleton [Ed.], Proceedings of the northeast raptor management symposium and workshop, Natl. Wildl. Fed., Washington, DC U.S.A.). More research is needed to determine if this population will show further signs of nesting adaptation on human-made structures.
We thank Brian Hardiman, Meesing Nature Center, and Tiffany Hardiman, for their field observations, Bradley Kreider, Wildlife Conservation Officer, Pennsylvania Game Commission, Dave Yosh and Bill Baker, Reliant Resources, Local Boy Scout Troop 37, and Keith Frerichs, Photographer.
Addendum: During winter 2005–06 and spring 2006, a pair of Bald Eagles, presumably the same birds, perched frequently on the nest platform and then occupied an abandoned raptor nest in a 20 m white pine (Pinus strobus) on power station property less than 1 km from the tall nest pole, where they fledged two young.