Electric-Utility Structures Associated with Raptor Electrocutions in Rural Areas

Although numerous studies have documented raptor electrocutions on distribution lines, few, if any, studies have examined the differential mortality of various structure types. We compiled and analyzed electric utility data from 1986 to 1996 on the occurrence of raptor electrocutions along electric...

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Bibliographic Details
Published in:Wildlife Society bulletin 2001-07, Vol.29 (2), p.612-623
Main Authors: Harness, Richard E., Wilson, Kenneth R.
Format: Article
Language:English
Subjects:
Animal Welfare
Aves
Birds
Birds of prey
Eagles
Electricity
Electricity distribution
Hawks
Mortality
Owls
Power lines
Seasons
Tangents
Transformers
Utility poles
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Summary:Although numerous studies have documented raptor electrocutions on distribution lines, few, if any, studies have examined the differential mortality of various structure types. We compiled and analyzed electric utility data from 1986 to 1996 on the occurrence of raptor electrocutions along electric distribution lines to determine which electric structures were correlated with raptor electrocutions. We gathered raptor-mortality records from 58 electric utilities that distribute power in rural areas of the western United States (U.S.). Of 1,428 electrocutions recorded, 96% were eagles, hawks, and owls. As in other studies, eagles, in particular golden eagles (Aguila chrysaetos), were electrocuted most often (748), with 66% of those aged represented by juvenile birds. Most eagle electrocutions were detected in late winter to early spring, whereas most hawk and owl electrocutions were detected in late summer. Eagle detection dates occurred when carcasses were discovered, thus carcasses may have gone undetected for many months, especially those covered by snow. Hawk and owl electrocutions dates were tied to outage records and represent a more accurate estimate of seasonal mortality. Of the 1,428 records, 421 eagle, hawk, and owl electrocutions were associated with specific utility structures. Transformers, especially banks of 3-phase transformers, were associated with a disproportionately large number of raptor electrocutions (53%), yet they commonly comprised few structure types (7-24% and 0-2.7% for 1- and 3-phase transformers, respectively). Certainly, there are potential biases associated with this type of observational data, but we argue that our results suggest that further research is warranted to quantify the relationships between raptor electrocutions and structure types. We conclude with recommendations to make transformers and other pole-mounted equipment safer for raptors, and we discuss the need for improved data collection, mitigation, and future research.
ISSN:0091-7648
1938-5463