The American Association of State Highway and Transportation Officials is “generally supportive” of a rule proposed in October by the U.S. Fish and Wildlife Service (USFWS) to develop a national migratory bird “incidental take mechanism” that also provides “flexibility” to state departments of transportation as construction seasons and bird breeding seasons vary across the country.

[Above photo of migratory swans by the U.S. Army Corps of Engineers]

The proposed rule regards the Migratory Bird Treaty Act of 1918, which protects migratory bird species between the United States and Canada. That law makes it unlawful without a waiver from the USFWS to “pursue, hunt, take, capture, kill, or sell” nearly 1,100 species of birds listed with the statute and does not discriminate between live or dead birds. It also grants full protection to any bird parts including feathers, eggs, and nests.

AASHTO stressed in a December 3 letter to the USFWS in a letter that it is desirable “to have a mechanism that allows state DOTs to propose bird management timeframes and best management practices” to limit migratory bird take.

AASHTO added that state DOTs do not support a general conservation fee as part of the transportation permitting process when migratory birds are involved. However, the organization noted that an “in-lieu fee approach” for individual transportation projects with unavoidable impacts could make sense depending on the details.

The Minnesota Department of Transportation is helping test ultrasonic bat “deterrence devices” at two bridges to help keep the mammals away from such structures when they undergo maintenance and/or repair activity.

[Above photo by the Minnesota DOT]

The agency noted in a blog post that bats like to roost in bridge expansion joints and temporarily preventing such roosting during bridge maintenance repair activity typically requires installing physical barriers that are often difficult to establish effectively, due to the design characteristics of many structures.

More importantly, the Minnesota DOT does not necessarily want to keep bats away permanently from its bridges because bat populations throughout North America are in serious decline. For example, the agency said white-nose syndrome – a fungal disease – has killed more than 5.7 million bats in eastern North America since 2005. On top of that, wind turbines kill hundreds of thousands of bats in North America annually, according to a study by the U.S. Geological Survey.

The Minnesota DOT has worked with the Minnesota Department of Natural Resources and the U.S. Fish and Wildlife Service for the last two years testing battery-operated ultrasonic deterrence devices that reduce bat activity at bridge site when activated, but ensure a quick return of bat roosting activity when deactivated.

“This project was innovative. We worked with a technology that wasn’t really on the market yet for real-world applications in anticipation of its availability,” noted Christopher Smith, wildlife ecologist with the Minnesota DOT’s Office of Environmental Stewardship.

He added that current regulations require shorter maintenance period options during the construction season in order to protect bats – mandating that crews must avoid having bats present during their work, which impacts cleaning, painting, and other maintenance timelines.

“The presence of bats disrupts bridge work timelines and budgets, and work upsets habitation for species struggling to survive,” Smith said.

The Minnesota DOT noted that it hopes to develop a procedure for deploying this ultrasonic bat deterrence technology when needed and determine associated expenses from this two-year research effort.

Further study could consider the technology in different configurations and environments, test the devices at many bridges around the country, and conduct a cost-benefit analysis, the agency added – while also comparing the “relative impact” of acoustic deterrents on specific bat species.