Dan Boone to VA-Bird: ridgeline migration and wind

Unlike in the west, the vast majority of birds likely to be killed at wind turbines in the east are neotropical migrants - which pass through our region mostly at night. Many of these species are already under severe pressure due to loss and fragmentation of breeding and wintering habitat.

To: va-bird

I've been following the exchanges about wind turbine impacts to wildlife and was puzzled about the participation of Mr. Tom Gray, who is the communications director and deputy executive director of the American Wind Energy Association - a "national trade association that represents wind power plant developers, wind turbine manufacturers, utilities, consultants, etc." Apparently Tom makes a habit of monitoring the list-servs of bird groups throughout the region (nationally?) in order to inject info or views favorable to the wind industry. I trust others are aware of Mr. Gray's role in this discussion, and hopefully note his bias when considering the information he selectively but generously provides.

His latest post to VA-Birds continues the long-standing efforts of avian consultants hired by developers of "industrial" windplants to dismiss or minimize concerns regarding wildlife impacts due to siting of very tall wind turbines along Appalachian ridges.

Unlike in the west, the vast majority of birds likely to be killed at wind turbines in the east are neotropical migrants - which pass through our region mostly at night. Many of these species are already under severe pressure due to loss and fragmentation of breeding and wintering habitat. Studies show that few of these kinds of birds are caught by cats or are hit by cars. Unfortunately, pro-wind advocates like to cite high bird mortality totals owing to other human structures while perhaps ignoring the overarching concern that cumulative impacts to these birds are additive, not relative.

While Mr. Gray is correct in his assertion that it is only a "theory" that birds might be channeled by prominent ridgelines such as found in VA, he fails to mention that this theory is actually supported by data - whereas the opinions of the wind industry's paid consultants have no data to support their self-serving claim that nocturnal bird migration is not influenced by mountainous terrain.

Dr. Paul Kerlinger is the principal avian migration consultant hired by wind energy developers here in the east. In numerous "Avian Risk Assessment" reports assessing wildlife impacts of proposed windplants in MD, PA and WV, Dr. Kerlinger routinely has dismissed concerns about harm to nocturnal migrants due to siting of extremely tall wind turbines atop prominent ridgelines (claiming ?night migrants are not known to follow ridges at night?). However, he has never studied the phenomenon of nocturnal avian migration in this region, and was not aware of (or failed to disclose the knowledge of) research that indicated ridges can indeed channel the movements of songbirds during night-time flights.

The fact that nocturnal migrant songbirds fly along and over ridge crests has been documented in the Central Appalachians for over 20 years, as the following excerpt from published research involving the region's first radar monitoring demonstrates:

"The patterns of migration detected in a mountainous area suggest that nocturnal migrants may well be influenced by topography. For the two nights we observed [Oct. 4 and 14, 1980] it appears that birds on the upwind side of the ridge were moving along the ridge, birds at the crest were moving along and over the ridge and few birds were found at low altitude on the downwind side of the ridge." Source: Seilman, M. S., L. A. Sheriff, and T. C. Williams. 1981. Nocturnal migration at Hawk Mountain, Pennsylvania. American Birds 35:906-909.

Furthermore, mountain ridges have been found to orient and concentrate night-migrating birds in Europe and elsewhere in the Appalachian Mountains of the United States. This following paper was published:

Williams, T.C., J.M. Williams, P.G. Williams, and P. Stokstad. 2001. Bird migration through a mountain pass studied with high resolution radar, ceilometers, and census. Auk 118:389-403;

and it concluded -

"Our observations and those of Bruderer and his coworkers [involving the Alps] indicate that broadfront migration should not be assumed for the passage of avian migrants over mountainous areas. That is important for evaluation of structures such as wind-powered electrical generators or communication towers on ridge lines. Although our studies were not designed to observe concentrations of migrants at topographical features, reaction of migrants to topography that we did observe suggested such concentrations during favorable and unfavorable conditions. Concentrations could result either as birds moved along a corridor, such as a pass or ridge line, or they could result from birds moving up and over a ridge meeting migrants already at that altitude and thus producing large numbers of birds a few tens of meters above the ridge summit. Our ceilometer observations of large numbers of birds near crests of ridges are particularly relevant in that regard."

Consequently, Dr. Kerlinger?s notion that nocturnal migrant songbirds do not follow or fly along Appalachian ridges at night is not corroborated by either of the two investigations of this phenomenon published to date. Furthermore, the observations by Williams et al. clearly show potential for concentrations of nocturnal migrants at altitudes and locations where wind turbines are being planned or erected. And the large bird kill at the WV windplant is indeed evidence that wind turbines do pose a collision hazard for nocturnal migrants.

Readers interested in seeing the distribution of communication towers in VA (or other states) should check the following website: and click on the state's outline on the map of the US. Few communication towers are identified in Highland County whereas proposals exist for many hundreds of 400-foot tall wind turbines to be erected in this locale.

Mr. Gray wishes to discount the importance of the 30 birds killed in one foggy night in late May 2003 at the WV windplant (all warblers and other neotropical migrants) - which comprised the largest wildlife mortality event ever recorded for a windplant anywhere in the world (until over 130 migratory bats were killed during a few days in August at the same industrial facility). However, it's very important to recognize that the number of birds and bats found at the WV windplant reflect only the carcasses found during once-a-week inspections of 44 wind turbines located in very rocky terrain that is difficult to search, particularly when looking for small birds or bats. In addition, the detection of the large songbird kill at the the WV windplant was due to turbine maintenance workers who observed a bobcat feeding on the bird carcasses and reported this to the graduate students hired to document the avian mortality of this facility.

So the number of bird carcasses found for the May mortality incident, and for this entire facility in 2003, would likely be only a small fraction of those that were actually killed. Other bird mortality studies have documented that up to 80% of carcasses disappear within 24 hours of hitting the ground. If scavengers are removing carcasses rapidly, the ratio of number carcasses found to number actually killed could be 1:10 or possibly 1:100.

Even if only 10-20 birds are killed on average at each turbine per year, this would add up to a major cumulative impact should the goal become reality that 20% of our region's electricity were generated by wind turbines. For VA alone, the 20% goal would require over 4,000 turbines to supply current demand - but that high number could double before 2025 to maintain this percentage since VA's demand for electricity is increasing at an annual rate of 3.1%.

The real problem for wind energy advocates is to show how this alternative energy source can reduce future adverse impacts due to coal mining and combustion given that our society's profiligate demand for electricity will likely far outpace the production capability that wind energy could supply from the entire eastern half of the US.

For bats, the situation appears far worse than for birds in terms of collision risk with wind turbines sited along Appalachian ridges. The level of bat mortality from the 44 turbines at the WV facility is on par with the annual bird kill recorded from all 5,000+ turbines at Altamont. Although 475 bat carcasses were found, the number likely killed was in the thousands to adequately reflect removals by scavenger and detection difficulties. The per turbine rate of mortality for bats at the WV windplant is 100s of times greater than at Altamont, and a similar high rate of bat mortality was found at the only other windplant in the southeast (in the Cumberland Mountains of eastern TN).

Contrary to Mr. Gray's claim, there is NO research currently ongoing to determine why bats collide with turbines - let alone research that examines how to prevent collisions. Realistically it could take many years (if ever) to find an effective deterrent that prevents bats from colliding with wind turbines. Yet the wind industry is pushing for siting of turbines with the promise of fixing the "problem" with bats in the future.

Sadly, the avian mortality research at the WV windplant failed to follow established protocols, and although the results have not been officially released yet - they may greatly underestimate the actual mortality attributable to collision with wind turbines. This research was funded by the wind energy developer, and overseen by the same consultant hired by the developer that predicted no significant impacts would result to avian wildlife. Lets hope that future wildlife studies at wind energy facilities are performed by researchers that are objective and independent of financial ties to the developer.

Dan Boone
DEC 31 2003
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