Noise studies: Studies find noise affects sage grouse
Cheyenne – A Jan. 9 meeting of the Sage Grouse Implementation Team focused on educating the group on new studies and information available related to sage grouse.
“Numerous studies have shown that there can be impacts of noise on vertebrate species,” said Gail Patricelli of the Department of Evolution and Ecology at the University of California Davis. “Studies are necessary to flush out the impact of noise on greater sage grouse.”
In looking at potential impacts from noise on sage grouse, Patricelli noted that their research team developed several recommendations to improve sage grouse habitats further.
“Noise is any background sound in the environment,” explained Patricelli. “For the purpose of our study, we looked at human-introduced noise.”
Particularly, Patricelli’s research team analyzed impacts from energy development on sage grouse habitats.
“Noise impacts might occur from the individual level to the population level,” she continued.
Individual noise impacts could come in the form of temporary or permanent hearing damage, increased predation risk, elevated stress levels and altered behaviors.
Additionally, it might lead to avoidance of otherwise suitable habitat, a masking of communication and reproductive stress, which could, in turn, impact population levels.
“Animals may not be able to be heard, and noise might mask important communication for mating or between hens and chicks,” Patricelli explained. “All of these things may scale up to the population level as habitat loss, reduced survival and productivity and, ultimately, population declines.”
Oil and gas development
“We have been interested in potential impacts of noise from energy development on greater sage grouse,” Patricelli commented. “It emerged as a result of robust studies that energy development is related to declines in greater sage grouse populations, and some studies that implicated noise as a probable cause of the declines.”
Because oil and gas development involves noisy infrastructure, such as generators, drilling rigs, compressor stations and traffic, Patricelli’s team set out to determine whether noise alone impacts grouse.
Beginning in 2006 on four leks, Patricelli’s team played drilling noise and road noise recorded from drilling activity in the Pinedale Anticline to sage grouse populations. Each lek was matched with a control lek that did not hear any noise. The leks were otherwise similar in population and location and were otherwise undisturbed.
In 2007-08, the team increased their research to include eight leks.
They utilized constant noise, designed to replicate drilling rigs, as well as intermittent noise as a result of traffic.
“We broadcast noise 24 hours a day, seven days a week for three breeding seasons,” explained Patricelli, adding that the project also involved use of dummy speakers in control leks.
“We did find a change in annual peak male count from a baseline percentage,” Patricelli commented.
By comparing lek counts to baselines data collected by the Wyoming Game and Fish Department and BLM, she said, “Noisy leks had lower male attendance than control leks.”
“Surprisingly, the effect size was much greater for road noise than drilling noise,” Patricelli explained. “We found a difference of 29 percent for drilling noise and 73 percent difference on road noise leks, which was surprising to us.”
In addition, the effects of noise were both immediate and sustained, with impacts being seen the first season.
“We also didn’t see any evidence of the birds habituating, or getting used to the noise,” she added.
In also looking at female lek attendance, they noticed a change in annual peak attendance, but small sample size and baseline data that wasn’t ideal led the group to say that the impact is suggestive, but not conclusive as related to female sage grouse.
“We also asked what happens to the birds that remain behind because not all the birds left,” Patricelli noted. “To address that question, we compared the levels of stress hormones from fecal samples.”
In analyzing stress hormones from fecal samples of sage grouse, Patricelli noted that the group also found impacts.
“There is a 17 percent increase in stress hormone levels on the noisy leks, compared to paired control leks,” she said. “Increased fecal corticosteroid indicated increased stress on noisy leks.”
Behavior of birds was also analyzed in the study, and Patricelli’s team noted that males did, in fact, change the timing of their displays based on road noise.
“Birds display 50 percent less often in noise events than expected by chance,” she said, “and they were strutting more often than expected during quiet periods.”
Similar to how humans may pause conversation to allow for passing of a loud vehicle, Patricelli noted that birds were displaying more frequently in quiet times.
“They may do this to reduce masking by strutting in quiet gaps so they can be better heard,” she said, as a possible explanation of the behavior.
Current regulation in non-core areas allows noise levels to exceed ambient levels by 10 decibels, a measure which is problematic for several reasons, according to Patricelli.
The team noted that current standards are too loud, measurement of noise at lek edge is insufficient for protecting sage grouse and approaches do not adequate address traffic.
“Defining ambient noise is very difficult,” said Patricelli of the problem with the current standard. “Outside of core areas, it allows up to 49 decibels to remain in compliance – that is too loud. That level is about as loud as an office or busy residential area.”
In fact, the noise emitted from the speakers used in the study was compliant with current restrictions.
“The actual ambient value is probably between 17 and 23 decibels quieter,” Patricelli said. “That is quite a huge difference in noise levels.”
Additionally, measuring at lek edge is insufficient, as Patricelli noted that nesting and brood rearing areas are not protected and can be plagued by loud noises.
“Areas surrounding leks are critical to supporting lekking and critical to support nesting and brood rearing,” she explained. “If the goal is to limit disruptive activity to sage grouse habitat, then we recommend noise measurements should be at the edge of the critical nesting and brood rearing habitat.”
“We want to acknowledge that noise is only one of many factors that may affect sage grouse populations,” commented Patricelli. “Noise mitigation should be a part of a comprehensive conservation strategy.”