Human-related causes of raptor mortality in western Montana: things are not always as they seem

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During the winters of 1997-98 and 1998-99, I investigated the causes, frequencies, and characteristics of human-related mortality of raptors in the Mission Valley, Montana, by systematically searching roadside corridors for dead birds. Surveys included primary and secondary roads, most of which were paralleled by power lines. I found a total of 126 dead raptors during the two winters, including 58 in 1997-98 and 68 in 1998-99. Nine different species were found, but most were rough-legged hawks (Buteo lagopus)(49%) and red-tailed hawks (Buteo jamaicensis)(29%). Of 88 birds collected and examined, 74 (84%) were shot, 8 (10%) were electrocuted, 4 (5%) died from unknown causes, 1 (1%) died by collision, and 1 (1%) died from predation. Those not examined were either too scavenged or too decomposed for necropsy, but they did not differ in location from those examined. Although 52% of dead birds were found directly beneath power poles or lines, and dead birds were found under a wide variety of pole configurations, very few were actually electrocuted. Furthermore, electrocuted birds were associated with only a few types of pole configurations, most of which included jumper wires and/or transformers. As for characteristics, shot birds more often had shattered bones and bruising and/or hematomas and were characterized by shearing of flight feathers, sprayed or spattered blood, and bullet fragments within entrance wounds. Electrocuted birds always showed some evidence of burns, but many (44%) required magnification optics to verify singeing of feathers. Curled, deformed, or incinerated talons also occurred with many electrocutions (33%). Consequently, although electrocutions and car collisions are well recognized as major causes of winter mortality of raptors, and continue to be major sources of raptor mortality around the world, in certain areas shooting may still be the leading cause of mortality.

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ELECTRONIC FILE - Zoology: Birds

Note that date of this publication is a bit confusing. On a title page, date is c2001, but at end of document, copyright date is 2002.

SWAP (2/19/2016) citation (but with editors added per CSE, and names and locations tweaked to fit CSE style):
Olson C. 2002. Human-related causes of raptor mortality in western Montana: things are not always as they seem. In: Carlton RG, editor. Avian interactions with utility and communication structures. Proceedings of a workshop; 1999 Dec 2–3; Charleston, SC. Palo Alto (CA): Electric Power Research Institute. p. 299–322. [accessed 2016 Feb 17]. http://www.epri.com/abstracts/Pages/ProductAbstract.aspx?ProductId=00000....