Raptor Electrocution in Tucson--Tucson Audubon Society

Tucson Audubon Society
Raptor Electrocution in Tucson
James F. Dwyer
(Article first appeared in the April 2004 Vermilion Flycatcher newsletter)

The issue of raptor electrocution in Tucson mirrors the national and global scenario. Across the U.S. and the world, raptors are dying of electrocution at appalling rates. Here in Tucson, this issue was first brought to our attention during a study by Jim Dawson and Bill Mannan looking at the natural history of Harris’ Hawks. Their work indicated that electrocution might be a major cause of mortality for raptors in the Tucson area. Tucson Electric Power Company (TEP) shares the concern of the Tucson Audubon Society and others in our community about this issue, and supported an investigative study. Some of the results of that effort are discussed here.

Harris Hawks on power pole in Tucson
(Photo courtesy of Tucson Electric Power)

Harris’ Hawks have some unique behavioral traits which put them at particular risk of electrocution. They are North America’s only social raptor. These birds can live in groups of 2-4 adults and 1-3 young, making up cooperative groups of up to 7 individuals who live and hunt together year round. Within these groups, individuals often perch together and demonstrate their social status by perch heights—dominant individuals perch higher than subordinates. Historically these demonstrations took place on the multiple arms of a mature saguaro or the branches of a dead tree. Today they often take place on power poles. This odd behavior dramatically increases the risk that at least one individual will wind up in a dangerous situation.

To further complicate the issue, in other parts of the American West we know that the most dangerous poles tend to be situated in high places overlooking open areas—poles on ridgelines, for example, or poles in agricultural areas. But TEP has a largely urban service area where that model doesn’t work well. If TEP is going to proactively protect the raptors in their service area from electrocution they need a better model. That’s where this study, focusing on the area within 300 meters of active Harris’ Hawk nests, comes in.

I located about 70 active Harris’ Hawk nests and moni-ored about 35 of those. My weekly monitoring visits consisted of examining power poles around nests for any evidence that a raptor had used that pole in the past week. I also monitored poles retrofitted in response to electrocution incidents to see if any more raptors were killed on those poles.

It is important to understand that the electrocution of raptors is not just a Tucson problem, but a problem on statewide, nationwide, and global levels. The data I present below were collected exclusively within TEP’s service area and they indicate a problem, but TEP has supported this project despite the risks of doing so and is responding positively to the results.

From February 1st through December 1st of last year, I detected a total of 73 raptor mortalities. Of those, 65% were confirmed electrocutions. Another 15% were suspected electrocutions. It is probably safe to group these together and say that roughly 80% of the raptor mortalities that I discovered during this period occurred as a result of contact with electric current. A breakdown by age and sex of the 43 confirmed Harris’ Hawks electrocutions that I detected illustrate two important points. The first is that roughly 70% of incidents involved young birds. The second is that about 15% of the electrocuted Harris’ Hawks I found were adult females, responsible for producing the eggs and raising and caring for young. These are experienced animals that under natural conditions are expected to have relatively low rates of mortality. We know from population modeling studies that if this portion of the population is reduced, the population overall usually declines. This fact especially is cause for concern.

To report raptor nests, or injured or dead raptors in the Tucson area, call:

Elissa Ostergaard, Ariz. Game and Fish Dept. (520) 628-5376 x4446
Tucson Electric Power Company (520) 623-7711 (most of the Tucson metro area)
Trico Electric Cooperative (520) 744-2944—ask for "Dispatch" (most areas surrounding the Tucson metro area)

Around the 35 nests I monitored, I found that roughly 25% of the poles that I identified beforehand as potentially dangerous did eventually kill a Harris’ Hawk. Overall, I detected 1.3 electrocution incidents per monitored nest. That means that on average, every single Harris’ Hawk nest that I monitored lost at least one individual to electrocution last year.

I detected a total of 43 confirmed Harris’ Hawk electrocutions and electric injuries last season. Another 20 were suspected, and an additional 13 raptors of other species were also found to have been electrocuted during this period. That adds up to a total of 76 detected incidents, and reflects a rate of 1 incident detected every four days for 10 months.

I also considered whether poles closer to nests are more dangerous than those farther away, and the answer is “yes,” at least for young hawks. Though for adults the answer is not as clear and I am continuing to investigate this relationship.

And finally, I am exploring whether “bird guarding” is effective. That is, I am asking the question, “When a pole is retrofitted to be safe for raptors, is that retrofitting effective?” Again, the answer turns out to be “yes.” Bird guarding works! But it only works if it’s applied thoroughly, both on individual poles, and on all poles in a territory. If the job is not done completely, the animals will just survive their contacts with the previously dangerous points which are now protected, and then be electrocuted at some other dangerous point on the same pole, or on the next pole down the line. Thoroughness in applying bird guards is something I’m working on with TEP.

I also wish to take this opportunity to ask you for your help. TEP has committed to protecting raptors in Tucson. But to do so they need to know what you know. Please, if you know of or suspect an electrocution incident, do call TEP’s customer service line at (520) 623-7711 or Elissa Ostergaard at the Arizona Game and Fish Department at (520) 628-5376 x4446. And, please, call immediately to report the incident. If you don’t tell them about it, they’ll never know, and nothing will be done. The other thing you can do is report raptor nests. If you’re aware of a nest, tell us about it! Doing so allows TEP to proactively protect the poles around those nests before an electrocution occurs, and that’s what we really want—to prevent these incidents from occurring in the future. Thank you for taking the time to read this, and thank you in advance for your help in resolving this issue.