ITD Builds Nesting Platforms for Osprey (PHOTOS)

BOISE, Idaho (News Release) – Many innovations start with meeting a need. This one came from an environmental and federal safety necessity.

The Federal Highway Administration requires an inspection of the 1,500-foot-long Dent Bridge every two years, but the Idaho Transportation Department could not inspect the overhead cable saddles because of nesting osprey, which are federally protected migratory birds.

The 45-year-old bridge spans the Dworshak Reservoir on the North Fork of the Clearwater River, north of Orofino.

“Inspectors needed to check the bridge, but could not inspect the top of the towers because of the nesting osprey,” said ITD Bridge Asset Management Engineer Dan Gorley. “Efforts in 2014 to remove the nests when they were unoccupied, in order to clear the area for inspection, only resulted in the birds returning to rebuild the nests in the same spot in 2015. Three huge, new nests appeared – each weighing at least 600 pounds.”

ITD needed to come up with an environmentally responsible plan to accommodate both the birds and the inspections.

Four new aluminum platforms were manufactured by ITD’s District 2 in early January and installed in late January. The new platforms were installed three feet above the current nesting areas, at the bridge’s crown, about 125 feet above the bridge’s driving surface. Each platform is about 5 feet wide by 5 feet long, and designed to hold up to 1,000 pounds.

By early April, four adult osprey could be seen occupying two separate nests with their families.

Biologists may be able to use some of the lessons learned from the osprey platforms to inform decisions in the future. For instance, the birds may use multiple platforms on the same bridge, if the platforms are far enough apart and there in a consistent food supply nearby. Providing these nesting opportunities for the osprey may also allow biologists more opportunity to observe the bird’s behavior.

A bridge inspection costs about $22,600, but cost for the platforms was around $10,000, which included materials, manufacturing and installation.